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Electronic Theses and Dissertations
2021
The Influence of Carcass Weight on Beef Primal Temperature, Tenderness, and Palatability
Samantha Egolf South Dakota State University
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Recommended Citation Egolf, Samantha, "The Influence of Carcass Weight on Beef Primal Temperature, Tenderness, and Palatability" (2021). Electronic Theses and Dissertations. 5274. https://openprairie.sdstate.edu/etd/5274
This Dissertation - Open Access is brought to you for free and open access by Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact [email protected]. THE INFLUENCE OF CARCASS WEIGHT ON BEEF PRIMAL TEMPERATURE,
TENDERNESS, AND PALATABILITY
BY
SAMANTHA R. EGOLF
A dissertation submitted in partial fulfillment of the requirements for the
Doctor of Philosophy
Major in Animal Science
South Dakota State University
2021 ii
DISSERTATION ACCEPTANCE PAGE Samantha R. Egolf
This dissertation is approved as a creditable and independent investigation by a candidate
for the Doctor of Philosophy degree and is acceptable for meeting the dissertation
requirements for this degree. Acceptance of this does not imply that the conclusions
reached by the candidate are necessarily the conclusions of the major department.
Judson K. Grubbs Advisor Date
Joseph P Cassady Department Head Date
Nicole Lounsbery, PhD Director, Graduate School Date iii
ACKNOWLEDGEMENTS
I would like to extend my gratitude to Dr. Kyle Grubbs for accepting me as a
Ph.D. student. Nobody said graduate school would be easy, especially with you as an advisor! I appreciate the advice you have given over the years. You have challenged me, not only academically and professionally, but personally, always encouraging me to look at the situation with a new perspective.
Thank you to Dr. Keith Underwood and Dr. Amanda Blair for serving on my committee and sharing your wealth of meat science knowledge with me. Keith, I am grateful for the opportunity to continue learning about meat processing from you. Thank you to you and your family for inviting me into your lives these past few years. Amanda, you challenged me to apply my work beyond the lab-to think about the producer and the packer. I am grateful for the tools and resources I accrued that will help me to continue being knowledgeable in the beef industry, as well as other livestock sectors.
Thank you to Dr. Jana Hanson for the assistance with my education research project. Your knowledge and expertise were greatly appreciated. Because of my education project, I have a greater appreciation for the education materials available, and
I feel I will be a better instructor in the future from what I gained.
A huge thank you goes to the meat science graduate students and Adam Rhody for your assistance with my project. The summer of 2018 will go down as one of our least favorite for all the long days spent in the beef plant, but I could not have completed data collection and processing without your help. I have learned so much from you all these past three years.
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Lastly, I would like to thank my family and friends for the love and support you have given me as I continued on my graduate school journey. I would not be here today if it were not for Dr. Jonathan Campbell encouraging me to pursue my Ph.D. A special thank you goes to my husband, Austin, for the encouragement and love. Thank you for enduring coolers and sprinklers to collect data for me and early mornings to do shear force and sarcomere work. Both of us in graduate school simultaneously was not easy at times, but I would not have done this with anybody else.
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TABLE OF CONTENTS
LIST OF FIGURES ...... vii LIST OF TABLES ...... ix ABSTRACT ...... x Chapter 1 ...... 1 Factors Influencing Beef Hot Carcass Weight ...... 2 Mechanisms of Tenderization ...... 3 Sarcomere Length ...... 4 Protein Degradation ...... 7 Background and the Bulk Density Effects ...... 9 Factors Impacting Tenderness ...... 10 Muscle Location and Fiber Type ...... 10 Quality Grade ...... 12 pH Decline ...... 14 Postmortem Chilling and Product Quality ...... 17 Current Industry Chilling Practices ...... 17 Influence of Increased Temperature on Product Quality ...... 18 Problem ...... 23 Objectives ...... 24 Literature Cited ...... 25 Chapter 2 ...... 32 Abstract ...... 33 Introduction ...... 34 Materials and Methods ...... 36 Carcass Selection and Internal Temperature Monitoring ...... 36 Statistical Analysis...... 37 Results ...... 38 Carcass Traits ...... 38 Temperature decline ...... 38 Discussion ...... 40 Conclusion ...... 44 Literature Cited ...... 45 Chapter 3 ...... 54 Abstract ...... 55 Introduction ...... 56 Materials and Methods ...... 58 Carcass Selection, Internal Temperature Monitoring, and Sample Processing58 Ultimate pH and Color ...... 60 Myofibril Isolation ...... 60 Sarcomere Length Determination ...... 61 Statistical Analysis...... 62 Results and Discussion ...... 62 Carcass Characteristics ...... 62
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Temperature Decline ...... 63 Ultimate pH and Color ...... 67 Sarcomere Length ...... 70 Conclusion ...... 71 Literature Cited ...... 73 Chapter 4 ...... 89 Abstract ...... 90 Introduction ...... 91 Materials and Methods ...... 92 Carcass Selection and Sample Processing ...... 92 Warner Bratzler Shear Force and Cook Loss ...... 93 Protein Extraction and Gel Sample Preparation ...... 93 Western Blot Analysis ...... 94 Statistical Analysis...... 96 Results and Discussion ...... 96 Warner Bratzler Shear Force ...... 96 Cook Loss ...... 99 Troponin-T Degradation ...... 102 Desmin Degradation ...... 103 Conclusion ...... 105 Literature Cited ...... 106 Chapter 5 ...... 125 Abstract ...... 126 Introduction ...... 127 Materials and Methods ...... 128 Carcass Selection and Sample Processing ...... 128 Consumer Sensory Panels ...... 129 Statistical Analysis...... 130 Results and Discussion ...... 130 Denver Cut Steaks ...... 130 Strip Steaks ...... 132 Eye of Round Steaks ...... 134 Conclusion ...... 138 Literature Cited ...... 139 Chapter 6 ...... 167
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LIST OF FIGURES
Figure 2.1 Data logger location in the round, chuck, and loin ...... 49 Figure 2.2 Interaction of hot carcass weight and quality grade for internal temperature decline of chuck primals of beef carcasses ...... 50 Figure 2.3 Interaction of hot carcass weight and quality grade for internal temperature decline of round primals of beef carcasses ...... 51 Figure 2.4 Internal temperature decline of loin primals of beef carcasses (n = 308) ...... 52 Figure 3.1 Data logger location in the round, chuck, and loin ...... 81 Figure 3.2 Steak fabrication guide for serratus ventralis, longissimus dorsi, and semitendinosus steaks ...... 82 Figure 3.3 Internal temperature decline in loin primals of USDA Select and low Choice beef carcasses ...... 83 Figure 3.4 Internal temperature decline in round primals of USDA Select and low Choice beef carcasses ...... 84 Figure 3.5 Internal temperature decline in chuck primals by of USDA Select (Se) and low Choice (LC) beef carcasses ...... 85 Figure 3.6 Representative color images of light weight and heavy weight semitendinosus steaks ...... 87 Figure 3.7 Representative sarcomere length images of light weight and heavy weight semitendinosus muscles ...... 88 Figure 4.1 Steak fabrication guide of the serratus ventralis, longissimus lumborum, and semitendinosus ...... 113 Figure 4.2 Mean (± SE) Warner-Bratzler shear force of the serratus ventralis, longissimus lumborum, and semitendinosus from USDA Select and low Choice carcasses ...... 114 Figure 4.3 Means (± SE) for cook loss of the serratus ventralis, longissimus lumborum, and semitendinosus from USDA Select and low Choice carcasses ...... 115 Figure 4.4 Representative Western blot for Troponin-T ...... 117 Figure 4.5 Means (± SE) for abundance of the 30 kDa troponin-T degradation product in the serratus ventralis from USDA Select and low Choice beef carcasses ...... 118 Figure 4.6 Means (± SE) for the abundance of the 30 kDa troponin-T degradation product in the longissimus lumborum from USDA Select and low Choicebeef carcasses ...... 119 Figure 4.7 Significant effects for the 30 kDa troponin-T degradation product in the semitendinosus from USDA Select and low Choice beef carcasses ...... 120 Figure 4.8 Representative Western blot of desmin ...... 121 Figure 4.9 Means (± SE) for the abundance of the 35 kDa desmin degradation product in the serratus ventralis from USDA Select and low Choice carcasses ...... 122
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Figure 4.10 Means (± SE) for the abundance of the 35 kDa desmin degradation product in the longissimus lumborum from USDA Select and low Choice carcasses ...... 123 Figure 4.11 Means (± SE) for the abundance of the 35 kDa desmin degradation product in the semitendinosus from USDA Select and low Choice carcasses ...... 124 Figure 5.1 Diagram of steak location for Denver cut, strip, and eye of round muscles . 148 Figure 5.2 Sample consumer sensory scales for intensity ratings and liking ratings ..... 149 Figure 5.3 Consumer sensory evaluation of USDA Select Denver steaks ...... 150 Figure 5.4 Consumer sensory evaluation of USDA low Choice Denver steaks ...... 153 Figure 5.5 Consumer sensory evaluation of USDA Select strip steaks ...... 155 Figure 5.6 Consumer sensory evaluation of USDA low Choice strip steaks ...... 158 Figure 5.7 Consumer sensory evaluation of USDA Select eye of round steaks ...... 161 Figure 5.8 Consumer sensory evaluation of USDA low choice eye of round steaks ..... 164
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LIST OF TABLES
Table 2.1 Carcass traits (means ± SE) of beef carcasses by grade within weight group .. 48 Table 3.1 Means (± SE) of carcass traits from USDA Select and low Choice carcasses selected to monitor internal temperature decline ...... 77 Table 3.2 Mean (± SE) for ultimate pH and color (Hunter L, a, b) of the serratus ventralis (SV), longissimus lumborum (LL), and semitendinosus (ST) from USDA Select and low Choice beef carcasses ...... 78 Table 3.3 Mean (± SE) for sarcomere lengths (µm) of steaks from the longissimus lumborum from USDA Select and low Choice beef carcasses ...... 79 Table 3.4 Mean (± SE) for sarcomere lengths (µm) of steaks from the serratus ventralis and semitendinosus muscles from USDA Select and low Choice beef carcasses ...... 80 Table 4.1 Means (± SE) for Warner-Bratzler shear force (kg) of steaks from USDA Select and low Choice carcasses ...... 109 Table 4.2 Means (± SE) for percent cook loss of steaks from the longissimus lumborum from USDA Select and low Choice carcasses ...... 110 Table 4.3 Means (± SE) for the abundance of the 30 kDa troponin-T degradation product for steaks from USDA Select and low Choice carcasses ...... 111 Table 4.4 Means (± SE) for the abundance of the 35 kDa desmin degradation product for serratus ventralis steaks from USDA Select and low Choice carcasses ...... 112 Table 5.1 Consumer demographics...... 141 Table 5.2 Consumer sensory evaluations of USDA Select Denver steaks ...... 142 Table 5.3 Consumer sensory evaluation of low Choice Denver steaks ...... 143 Table 5.4 Consumer sensory evaluations of USDA Select strip steaks ...... 144 Table 5.5 Consumer sensory evaluations of USDA low Choice strip steaks ...... 145 Table 5.6 Consumer sensory evaluations of USDA Select eye of round steaks ...... 146 Table 5.7 Consumer sensory evaluations of USDA low Choice eye of round steaks .... 147
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ABSTRACT
THE INFLUENCE OF CARCASS WEIGHT ON BEEF PRIMAL TEMPERATURE,
TENDERNESS, AND PALATABILITY
SAMANTHA R. EGOLF
2021
The United States beef industry has experienced increasing hot carcass weights
(HCW) and improvements to quality grade the last three decades. Postmortem chilling of beef carcasses is critical to overall product quality. Carcass weight and composition may influence carcass temperatures during postmortem chilling. The objective of this research was to evaluate the effects of HCW and quality grade during postmortem chilling and on product quality. A-maturity carcasses were selected by weight [light = 296–341 kg; middle = 386–432 kg; heavy = 466–523 kg]. A 20 cm data logger was placed into the chuck and round and a 10 cm data logger placed in the loin. Muscles from a subs-sample of USDA Select and low Choice carcasses were collected for further analyses. Ultimate pH and color (Hunter L, a, and b) were measured at the time of steak fabrication. Steaks were aged 5 d for sarcomere length and 5, 10, or 14 d for Warner Bratzler shear force, cook loss, troponin-T and desmin degradation, and consumer sensory analyses.
Generally, heavier carcasses with improved quality grade retain heat for an extended period of time. No differences were observed for ultimate pH across weight groups, but ultimate pH was increased from Select to low Choice serratus ventralis muscles. Heavy weight carcasses had higher L, a, and b values compared to lighter carcasses in the serratus ventralis, longissimus lumborum, and semitendinosus muscles
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(P < 0.05). Shorter sarcomeres were observed in heavy weight semitendinosus muscles (P
< 0.05).
In the longissimus lumborum, Warner Bratzler shear force was highest in light weight steaks aged 5 d (P < 0.05). By 10 d of aging, no differences were observed between weight groups for tenderness. Protein degradation was also influenced by HCW in all three muscles. In general, sensory attributes of steaks from middle weight carcasses had higher scores overall compared to steaks from light and heavy weight carcasses in all muscles. These data demonstrate HCW can influence temperature decline and overall product quality. Additional research to further explore the impact of HCW and quality grade on temperature decline will help improve chilling systems for the beef industry to continue producing high-quality beef products.
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Chapter 1
Literature Review
2
Beef hot carcass weights (HCW) in the United States have increased an average of 2.3 kg per year over the last three decades culminating in approximately a 70 kg increase (USDA-ERS, 2019). Simultaneously, average backfat thickness (1.32 0.12 cm) has remained consistent (NCBA, 2016a), indicating the observed increase in HCW over the past 30 years is a result of increased muscle (lean) mass and internal fat
(visceral, intermuscular, and intramuscular) deposition. In 2016, 70% of carcasses received a quality grade of USDA Choice or Prime compared to 55% in 1991 (NCBA,
2016a) demonstrating increased intramuscular fat deposition. Increased lean and intramuscular fat can be attributed to an increased understanding of beef nutrition and growth (Bruns et al., 2004), utilization of beta agonists and growth promoting technologies (Ebarb et al., 2016), improved genetics, and selection for carcass characteristics.
Factors Influencing Beef Hot Carcass Weight
Beef HCW and carcass composition are the result of a combination of factors.
Between and within cattle breeds, cattle are market-ready at different times due to frame size. Larger framed beef cattle generally require additional days on feed and produce heavier carcasses with more muscling. Additionally, carcasses from male cattle are heavier and leaner than their female counterparts (Marchello et al., 1970; Martin et al.,
1971; Park et al., 2002; Choat et al., 2006).
Diet, length of time on a finishing diet, and season during the finishing stage can impact carcass composition (Marchello et al., 1970; Bruns et al., 2004). Marchello et al.
(1970) reported summer-fed cattle had increased carcass weights, deposited more
3 subcutaneous fat, and had a more desirable quality grade than winter-fed cattle. The advances in knowledge of growth and maintenance requirements for market cattle has enabled nutritionists to formulate rations to promote the appropriate tissue growth (i.e. muscle or fat). Growing cattle will use energy first for maintenance, followed by bone growth, then protein accretion, and deposit excess energy in fat depots (Hammond, 1940;
Bruns et al., 2004; Kern et al., 2014). Nutrient utilization can be manipulated through the use of growth-promoting technologies to repartition nutrients to muscle growth instead of fat deposition (Pendlum et al., 1978; Scramlin et al., 2010; Ebarb et al., 2016). Many fed cattle receive a growth implant or feed additive to optimize feedlot performance resulting in heavier muscled carcasses (Strydom et al., 2009; Ebarb et al., 2016). Heavier HCW and changes in carcass composition may influence postmortem chilling rates and biochemical changes, product quality, and consumer sensory evaluations of beef products as previously reported by Djimsa et al. (2019), Fevold et al. (2019) and Lancaster et al.
(2020).
Mechanisms of Tenderization
Following slaughter, a series of biochemical changes occur resulting in rigor mortis and tenderization of meat. During the first few hours postmortem, the carcass attempts to maintain homeostasis. Metabolism during this time will shift from aerobic, or using oxygen, to anaerobic, or lacking oxygen (Huff Lonergan et al., 2010). Anaerobic metabolism uses glycolysis to produce energy, which results in the production of lactate and hydrogen byproducts that decrease the pH (Huff Lonergan et al., 2010). Muscles enter rigor mortis when adenosine triphosphate (ATP) is depleted and muscles are no
4 longer able to contract and a set sarcomere length is established. During postmortem aging, proteins are broken down via proteolytic systems resulting in loss of structural integrity and tenderization (Huff Lonergan et al., 2010).
Sarcomere Length
Skeletal muscle is comprised of individual units called sarcomeres that allow the muscle to change length and tension to contract and relax (Ertbjerg and Puolanne, 2017).
Sarcomeres are made up of proteins that help maintain structural integrity (i.e. titin and desmin), regulate contraction (i.e. tropomyosin and troponin), and perform contraction
(i.e. myosin and actin; Ertbjerg and Puolanne, 2017). Titin, a structural protein, connects the z-disk to the M-line in the thick filament and acts like a spring during contraction
(Ertbjerg and Puolanne, 2017). Maximum sarcomere lengths (up to 3.7 m) occur when titin is completely stretched (Locker and Hagyard, 1963). At the other extreme, maximum shortness occurs when the z-disk touches the thick filament, which is 1.5 m in length. During extreme contraction, the thick filament can penetrate the z-disk.
Sarcomere lengths have been reported as short as 0.7 m during extreme contraction
(Locker and Hagyard, 1963). However, sarcomere lengths under 1.4 m are rare because they exceed the biological minimum (length of the thick filament) and cause loss to muscle structural stability (Locker, 1959).
In muscle, contractions occur when calcium released from the sarcolemma binds to troponin-C in the thin filament resulting in a conformational change in the troponin complex (Aberle et al., 2001). This conformational change moves tropomyosin, exposing the binding site on actin. Myosin is able to form cross-bridges with actin, pulling the thin
5 and thick filaments closer together so they have a greater degree of overlap. After crossbridge formation, ATP is hydrolyzed and the energy from the hydrolysis causes myosin to break from actin (Aberle et al., 2001). Provided sufficient calcium and ATP concentrations, the binding and breaking of myosin to actin continues. If calcium is resequestered into the sarcolemma or ATP depleted, muscle will no longer be able to contract or relax (Aberle et al., 2001).
The same process is utilized for muscle contraction during the rigor process.
Calcium is released from the sarcolemma allowing sarcomeres to undergo contraction.
Muscle attempts to rephosphorylate adenosine diphosphate to maintain ATP levels
(Ertbjerg and Puolanne, 2017). Postmortem ATP production is through aerobic metabolism until oxygen is depleted, then the system switches to anaerobic metabolism, in which case ATP is a product of glycolysis (Huff Lonergan et al., 2010). Once ATP is no longer synthesized and the stores depleted, permanent cross-bridges are formed between myosin and actin and the sarcomere no longer extensible.
Post-rigor sarcomere length can be influenced by muscle location on the carcass.
Increasing tension, or force on muscles, results in increased sarcomere lengths. As the amount of tension varies throughout a muscle, so too will sarcomere length (Rhee et al.,
2004). Devine et al. (1999) demonstrated the importance of muscle attachment to the skeletal structure to sarcomere length in restrained and unrestrained beef longissimus lumborum muscle. Sarcomere length was longer in restrained muscle than in the unrestrained muscle demonstrating the importance of tension to sarcomere length during the rigor process.
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Sarcomere length has an established link with tenderness with shorter sarcomere lengths resulting in decreased tenderness (Locker, 1960; Herring et al., 1965; Marsh and
Leet, 1966; Wheeler and Koohmaraie, 1994). Locker (1960) reported increased Warner
Bratzler shear force (WBSF) values in psoas major and psoas minor muscles with shortened sarcomeres in Prime beef carcasses. Herring et al. (1965) reported similar findings in the psoas major and semitendinosus muscles from Choice carcasses. Marsh and Leet (1966) reported at ~40% sarcomere shortening, sternomandibularis muscles were the least tender. Sternomandibularis muscles with 60% sarcomere shortening had similar WBSF values to sternomandibularis muscles with 20% sarcomere shortening
(Marsh and Leet, 1966). The extreme shortening and associated tenderness may be a result of myofibrillar disruption and loss of structural integrity of the muscle.
The strength of the relationship between sarcomere length and tenderness can vary based upon when sarcomeres are analyzed. Wheeler and Koohmaraie (1994) reported sarcomere lengths of 1.75 µm in lamb carcasses at the time of rigor mortis and lengths of 1.9 µm at 13 d postmortem. Similar observations were observed by Gothard et al. (1966) in beef longissimus dorsi and semimembranosus muscles and Stromer et al.
(1967) in the beef semitendinosus muscle. During the postmortem aging period, proteins are degraded, which results in loss of structural integrity of the muscle. In the sarcomere, the thin filament is attached to the z-disk by α-actinin (Taylor et al., 1995). As proteins in the z-disk and thin filament are degraded, the sarcomere begins to lose its structure
(Taylor et al., 1995). Additionally, as titin is degraded, there is no protein to maintain the connection, and thus length, between the z-disk and thick filament. The changes occurring to sarcomere structure during the postmortem period show the importance of
7 stating when sarcomere samples are collected and analyzed and to which aging days the sarcomere lengths are being correlated as it may impact the results of the strength of the sarcomere-tenderness relationship.
Protein Degradation
The calpain system is thought to be responsible for the majority of postmortem proteolysis (Koohmaraie, 1992). The calpain system is comprised of calpain-1, calpain-2, and calpastatin. Calpain is activated by calcium (2–80 µmol for calpain-1 and 200–800
µmol for calpain-2) and inhibited by calpastatin (Goll et al., 2003). Under postmortem conditions, calcium is released from the sarcoplasmic reticulum and binds to calpain. In its inactive form, calpain is 80 kDa. Upon activation, calpain-1 autolyzes from 80 kDa to the active 78 kDa product (Goll et al., 2003). Once active, calpain degrades proteins, including itself. Further autolysis renders calpain inactive (Goll et al., 2003). Most postmortem protein degradation occurs because of calpain-1 due to insufficient amounts of calcium available in the postmortem system to activate calpain-2. The conditions for optimum calpain-1 activity are 25ºC at pH 6.5 (Boehm et al., 1998). To confirm the role of calpain-1, Huff-Lonergan et al. (1996) studied the effect of calpain-1 on multiple proteins, including troponin-T and desmin, and determined that the majority of postmortem protein degradation and tenderization could be caused by calpain-1.
The rate and extent of the degradation of muscle proteins during postmortem aging can impact product tenderness (Huff Lonergan et al., 2010). Proteins that can be analyzed to assess protein degradation include troponin-T (TnT), desmin, and calpain-1.
Troponin-T is a 37 kDa regulatory protein that is known to degrade into a 30 kDa TnT
8 product (MacBride and Parrish Jr., 1977; Olson and Parrish Jr., 1977; Huff-Lonergan et al., 1996). Loins from veal, A-maturity and C-maturity beef carcasses were analyzed by
Olson and Parrish Jr. (1977) to determine the correlation of TnT to tenderness. In more tender steaks, the 30 kDa TnT degradation product appeared in greater density and was highly correlated to shear force, explaining over 50% of the tenderness variation
(MacBride and Parrish Jr., 1977; Olson and Parrish Jr., 1977). Troponin-T has been found to contribute to protein degradation due to its association with the I-band, which breaks down during the aging process (Huff-Lonergan et al., 1996). The I-band, which is made up of actin, the troponin complex, and tropomyosin, along with other proteins, spans the distance between thick filaments. As proteins in the I-band are degraded, the thin filament loses its structural integrity. Although troponin-T is not indicative of tenderness, it does contribute to the tenderization process.
Desmin is a structural protein that connects myofibrils at the point of the z-disk.
The 55 kDa intact desmin product has been found to be associated with postmortem aging as an indicator of overall protein degradation (Hwan and Bandman, 1989; Whipple and Koohmaraie, 1991). As the abundance of the intact desmin decreases, WBSF values decrease. At elevated temperatures (≥25°C), it may be possible to accelerate desmin degradation to improve tenderness at earlier postmortem aging times (Hwan and
Bandman, 1989). This is most likely due to temperatures providing optimal conditions for calpain-1 activity, for which desmin is a substrate. Under normal chilling temperatures
(4°C), the majority of desmin degradation occurs within the first few days postmortem and is mostly degraded by three weeks of aging (Hwan and Bandman, 1989).
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Background and the Bulk Density Effects
Connective tissue and fat impact perceived tenderness of beef products. The background effect relates connective tissue to meat tenderness. As the abundance of connective tissue increases, steaks are going to be perceived as less tender. This is because connective tissue is not highly degraded by proteolytic enzymes during postmortem aging and requires high heat for extended periods of time to be broken down
(Christensen et al., 2013). Increasing fat makes a product seem more tender. Fat has a lower resistance to shear force, making the product seem more tender. The “bulk density,” or “lubrication,” effect, first proposed by Smith and Carpenter in 1974, explains the role of marbling to the eating experience. Bulk density is the concept that, per unit volume, fat will dilute lean tissue, making the product seem more tender (Savell and
Cross, 1988). Fat within the muscle also lubricates the muscle fibers, making the product seem juicier.
Historically, the use of muscles from the chuck and round are used as ground product and roasts because of increased connective tissue content and decreased fat content in the round making some muscles appear less tender. Research has been devoted to identifying chuck and round muscles that can be marketed as steaks and increase carcass value (Smith et al., 1978; Calkins and Sullivan, 2007; Nyquist et al., 2018). Smith et al. (1978) aged several muscles from the chuck and round and conducted WBSF tests across a 28-d aging period. Of the muscles observed, the infraspinatus muscle (Flat iron) and serratus ventralis (Denver cut) were amongst the most tender muscles after 28 d of aging (2.5 kg and 2.4 kg, respectively). Nyquist et al. (2018) reported WBSF values for the infraspinatus and serratus ventralis at 21 d of aging at 2.16 kg and 2.04 kg,
10 respectively. From the round, the semimembranosus muscle (top round) has been reported to have an acceptable tenderness level of 4.0 kg or less (Smith et al., 1978;
Nyquist et al., 2018). However, the top round is often cut into roasts or used for sliced beef due to its size and low fat composition. A smaller muscle from the round, the semitendinosus (eye of round) provides a more economical steak option for consumers seeking lean cuts of beef, but the eye of round has WBSF values of 4.7 kg (Smith et al.,
1978; Calkins and Sullivan, 2007). Miller et al. (2001) reported consumers begin to categorize steaks as “more tender” or “less tender” at 4.6 kg. Therefore, the eye of round steak, although economical, may not provide a positive eating experience for consumers.
Factors Impacting Tenderness
Tenderness is the most important factor for consumer selection of beef products, followed closely by flavor (Miller et al., 1998; Calkins and Sullivan, 2007). Providing consistently tender products has been a challenge for the beef industry. Tenderization is the result of a combination of intrinsic factors, such as muscle location (Rhee et al., 2004;
Wheeler et al., 2007), muscle composition (Smith et al., 1985) and fiber type (Calkins et al., 1981; Klont et al., 1998; Kirchofer et al., 2002), and quality grade (Miller et al., 1997;
O'Quinn et al., 2012) and postmortem factors, such as rate and extent of pH decline (Yu and Lee, 1986; Purchas, 1990; Rathgeber et al., 1999; Sammel et al., 2002).
Muscle Location and Fiber Type
Locomotive muscles, such as muscles found in the chuck and round, can be less tender compared to cuts from support muscles, such as the rib and loin. In comparison to
11 support muscles, locomotive muscles have increased connective tissue and a decreased fat content is observed in muscles from the round. Differences observed in tenderness can be explained by the background and bulk density effects. As the percent connective tissue increases, products are perceived as less tender; as percent fat increases, products are perceived as more tender (Smith et al., 1985; O’Quinn et al., 2012).
Within-muscle tenderness also varies. Rhee et al. (2004) analyzed the within- muscle location effect on both support and locomotive beef muscles and reported a location effect in five of 11 muscles analyzed (psoas major, semitendinosus, biceps femoris, semimembranosus, and rectus femoris). This variation in tenderness within a muscle was linked to sarcomere length and collagen content (Rhee et al., 2004). Bratcher et al. (2005) determined a within-muscle location effect for WBSF in the complexus, rhomboideus, vastus lateralis, and rectus femoris. Warner Bratzler shear force values decreased in the complexus and rhomboideus from the anterior to posterior ends of the muscle, whereas the rectus femoris increased in WBSF from anterior to posterior. The vastus lateralis increased in WBSF from the dorsal to ventral side of the muscle. Wheeler et al. (2007) reported decreased sliced shear force values at either end of the longissimus muscle and increased sliced shear force values in the middle of the muscle. The effects of tension, or force, on individual muscles throughout the carcass varies, explaining the gradients in shear force values throughout muscles (Rhee et al., 2004; Nian et al., 2018).
Tension to individual muscles comes from attachment to the skeleton and adjacent muscles and suspension method used during postmortem chilling.
Muscle fiber type has been reported to be an indicator of tenderness (Calkins et al., 1981). Type I muscle fibers are slow-twitch muscle fibers that primarily use oxidative
12 processes to function, while Type II muscle fibers are characterized as fast-twitch muscle fibers that primarily use glycolytic metabolism to function (Klont et al., 1998). Type I muscle fibers have a small diameter and are associated with increased myoglobin content, making these fibers appear more red. Type II fibers can be further divided into Type IIA
IIX, and IIB. In comparison to Type I fibers, Type IIB fibers are larger and have a decreased myoglobin content making them appear more white. Type IIA and IIX fibers are intermediate fast-twitch fiber types between Type I and Type II using both oxidative and glycolytic metabolic processes (Klont et al., 1998). Fiber type is thought to impact the rate of aging and protein degradation, and, thus, tenderization. In comparison to Type
I muscle fibers, aging of Type II muscle fibers is thought to be more rapid due to a higher calpain/calpastatin ratio (Koohmaraie, 1996; Klont et al., 1998; Lee et al., 2010).
Although Type II muscle fibers may have an increased aging rate, these muscle fibers are typically higher in connective tissue, have less adipose tissue, and are less tender than
Type I muscle fibers (Calkins et al., 1981; Kirchofer et al., 2002).
Quality Grade
Quality grade has been demonstrated to be an estimate of palatability and consumer eating experience. Consumers rate steaks of increasing quality grade more tender, juicier, and more flavorful (Smith et al., 1985; Miller et al., 1997; O'Quinn et al.,
2012; Nyquist et al., 2018).
For A-maturity beef carcasses (<30 months), the United States Department of
Agriculture (USDA) has three quality grades most commonly used to market beef products to food establishments and consumers: USDA Prime, Choice, and Select
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(USDA-AMS, 2021). Although not common, carcasses could receive a USDA Standard or Commercial quality grade. Carcasses that grade USDA Choice can be further separated into low Choice and upper 2/3 Choice. The division between upper 2/3 Choice and low Choice is important to branded beef programs in the United States, where products can be marketed for a premium due to the positive eating experience consumers can expect. Quality grade is assigned based upon the amount of intramuscular fat, or marbling, in the ribeye as observed between the 12th and 13th rib following chilling and a
15-20 min bloom period; skeletal maturity; and lean color and texture (USDA-AMS,
2021). Prime carcasses have the greatest amount of marbling, over 9.9% intramuscular fat (Wilson et al., 1999). Low Choice carcasses have 4.0–5.7% intramuscular fat and upper 2/3 Choice carcasses have 5.8–9.8% intramuscular fat (Wilson et al., 1999). Select carcasses have 2.3–3.9% intramuscular fat (Wilson et al., 1999), and Standard and
Commercial carcasses have less than 2.0% intramuscular fat (Legako et al., 2015). Given the increased fat content of Prime steaks (>10% intramuscular fat), the bulk density effect likely explains why those products are often perceived as being more tender, compared to lower quality grading steaks with less than 4.0% fat.
The positive relationship between quality grade and tenderness has been the focus of multiple studies in an effort to evaluate the consumer eating experience. Smith et al.
(1985) reported Prime and upper 2/3 Choice longissimus dorsi steaks had no difference in tenderness or overall palatability. There was a detectable difference between upper 2/3
Choice and low Choice for tenderness; however, consumers gave similar overall palatability ratings for both upper 2/3 Choice and low Choice. A nationwide consumer palatability and trained sensory panel study conducted by Savell et al. (1987) confirmed
14 the findings of Smith et al. (1985). The 2016 National Beef Tenderness Survey (NCBA,
2016b) reported Prime steaks were more tender in comparison to high Choice, low
Choice, and Select steaks. Prime beef products have consistently been shown to have an improved eating experience over low Choice and Select products. Low Choice beef products are often considered as having better eating quality than Select beef products.
Platter et al. (2003) used consumer evaluations of tenderness, juiciness, and flavor to create a model to predict consumer acceptance of steaks with varying WBSF values and quality grade. The model from Platter et al. (2003) shows as quality grade increases from
Select to low Choice, consumer acceptance increases O'Quinn et al. (2012) reported higher consumer ratings for low Choice strip steaks for tenderness, flavor, and overall liking compared to Select strip steaks. However, some studies have reported no differences for overall palatability between USDA Select and low Choice beef products.
Smith et al. (1985) reported no differences in palatability of Good (now USDA Select) and low Choice ribeye and top round steaks. Nyquist et al. (2018) reported low Choice steaks across nine muscles had higher consumer ratings for juiciness and flavor, but overall liking was not different from Select steaks.
pH Decline
The pH of living muscle is 7.2–7.4 but decreases to approximately 5.4–5.8 as lactate and H+ ions accumulate during postmortem metabolism (Huff Lonergan et al.,
2010). Both the rate and extent of pH decline influence product quality. Rate of pH decline has been studied extensively in pork carcasses due to pale, soft, and exudative
(PSE) pork. Although not common in the beef industry, PSE-like conditions are observed
15 in muscles experiencing a rapid pH decline while maintaining elevated temperatures for an extended period of time. A rapid pH decline negatively impacts meat quality by reducing water holding capacity (WHC; the ability of muscle to retain water), increasing cook loss, reducing muscle color quality, and reducing protein extraction capability due to increased protein denaturation (Rathgeber et al., 1999; Sammel et al., 2002; Kim et al.,
2012). Individual muscles experience different rates of pH decline and within muscle pH decline variation also exists due to a combination of factors, one of which is muscle fiber type. Type II muscle fibers are least susceptible to an increased rate of pH decline due to the increased glycolytic activity that provides a buffering capacity (Devine et al., 1984;
Aalhus and Price, 1991). Rate of pH decline will also vary within a muscle. A significant increase in the rate of pH decline in the deep semimembranosus compared to the superficial semimembranosus has been reported by Sammel et al. (2002) and Lancaster et al. (2020). The difference in the rate of pH decline within the semimembranosus was due to the higher temperature and slower rate of temperature decline observed in the deep portion of the muscle.
The extent, or ultimate pH (pHu), of pH decline will affect product quality influencing WHC, color, and tenderness. A positive relationship exists between pHu and
WHC. Purchas (1990) reported increased pHu decreased cook loss and expressed juices in bull and steer longissimus dorsi muscles, indicating an increased WHC capacity.
Proteins are able to bind to water molecules at sites either positively or negatively charged. When pHu approaches the isoelectric point of meat at pH 5.1, the number of positive and negative charges found on proteins is equal, resulting in decreased water binding and increased water loss. Muscles with a higher pHu will have an increased WHC
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compared to muscles with a lower pHu. In addition to increased WHC, high pHu muscles are dark red to purple in color (Abril et al., 2001). Hughes et al. (2017) reported darker longissimus thoracis muscles had increased pHu and myofibril widths and shorter sarcomere lengths compared to the lighter muscles. As pH decreases, myofibrils have been reported to shrink, increasing the space between myofibrils (Heffron and Hegarty,
1974; Offer and Trinick, 1983). The decreased space between myofibrils and shortened sarcomere lengths increase the protein density of the muscle, which has been postulated to increase light absorption and decrease light reflectance making the product appear darker (Hughes et al., 2017).
A curvilinear relationship between tenderness and pHu has been reported by
Bouton et al. (1973) and Yu and Lee (1986). Bouton et al. (1973) reported a curvilinear relationship between pHu and tenderness in beef longissimus dorsi and semimembranosus muscles. Tenderness was increased in steaks with a pHu of 5.8–6.0. Yu and Lee (1986) reported a similar relationship between pHu and tenderness of beef longissimus muscle with pHu <5.8 (low), 5.8–6.3 (intermediate), >6.3 (high). Steaks from high pHu longissimus muscles were the most tender followed by the low pH steaks, and intermediate steaks were the least tender. Yu and Lee (1986) proposed intermediate steaks (pHu 5.8–6.3) were the least tender because pHu influences protease activity.
Intermediate pHu steaks have a pHu range in which conditions are not ideal for optimal protease activity (Yu and Lee, 1986). However, it is known proteolytic enzymes can continue to function between pH 5.8–6.3 as demonstrated by Koohmaraie (1992),
Maddock et al. (2005) and Bee et al. (2007).
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Postmortem Chilling and Product Quality
Current Industry Chilling Practices
Following slaughter, beef carcasses enter a hotbox, which is a cooler designed to chill carcasses from normal body temperature (38.9C) to below 4.4C. Hotbox capacity varies based on holding capacity, number of rails, rail length, carcass size, chilling system utilized, and spacing between carcasses. Crowding of carcasses is not recommended so as to minimize moisture loss and shrinkage and allow for proper chilling (Allen et al., 1987). Carcasses that maintain higher temperatures for a longer period of time have increased drip loss caused by protein denaturation (den Hertog-
Meischke et al., 1997). Due to the high operational cost of chilling systems, facilities will push carcasses as close together as possible to maximize space utilization, potentially decreasing chilling efficiency (Allen et al., 1987; Gill et al., 1991). Following chilling, carcasses are ribbed between the 12th and 13th rib to be presented for grading. Following grading, carcasses are generally relocated to a holding cooler to continue chilling until fabrication. Time spent by carcasses in coolers prior to fabrication varies between beef packing plants. Plants generally grade beef carcasses 24 to 48 h postmortem and fabricate shortly thereafter.
The beef industry uses chilled air movement or air movement in addition to an intermittent cold-water spray to decrease carcass temperatures during postmortem chilling. The use of spray chilling systems was introduced to the beef industry nearly 50 years ago with the goal of chilling carcasses at an increased rate to improve product quality and safety and decrease shrinkage (Hansen et al., 1973; Jones and Robertson,
1988; Prado and de Felício, 2010). These spray chill systems not only reduce shrinkage,
18 but carcass temperatures have also been reported to decrease more rapidly when water is intermittently applied to the surface (Savell, 2012). The average beef carcass size was
288 kg when early spray chilling systems were introduced to the meat industry, and the beef carcasses of today’s cattle average 367 kg (USDA-ERS, 2019). The additional weight entering hotboxes increases the incoming heat load to the cooler, which the system may not be able to properly handle to efficiently chill carcasses.
Alternative chilling methods include the use of very rapid chilling procedures.
Very rapid chilling of beef carcasses is not common, unlike the pork industry because of the ultra-low temperatures used. Very rapid chilling uses ultra-low temperatures, as low as -70℃, to rapidly reduce the temperature of carcasses to 4C within 24 h post- slaughter. The use of these ultra-low temperatures to chill a beef carcass could result in cold shortening of some muscles, like the loin and rib. It has been demonstrated there is potential to use very rapid chilling in the beef industry to prevent carcass shrinkage and increase plant efficiency (Bowling et al., 1987; Aalhus et al., 2002). However, very rapid chilling also results in muscles with dark color and increased drip loss during storage
(Aalhus et al., 2002). Additional research regarding the use of very rapid chilling in the beef industry is required prior to industry wide adoption. Research needs to determine the optimum chilling temperature and time to minimize the negative impacts of blast chilling on product quality.
Influence of Increased Temperature on Product Quality
Tenderness, one of the most important sensory attributes to consumers, is directly impacted by muscle location and composition, sarcomere length, and postmortem
19 proteolysis. The mechanism responsible for tenderization can be impacted by internal carcass temperature. Internal carcass temperature can also impact product quality attributes such as juiciness, color, and flavor.
A rapid pH decline decreases WHC, increases cook loss, and decreases juiciness.
High carcass temperatures and a rapid pH decline have been reported to occur simultaneously in turkey breast (Rathgeber et al., 1999), pork longissimus (Lindahl et al.,
2006), beef longissimus dorsi (White et al., 2006), and beef longissimus lumborum muscles (Kim et al., 2012). Mechanisms proposed to explain the relationship between rate of pH decline and temperature include ATPase and glycogen debranching enzyme activity. Scopes (1974) proposed the amount and activity of ATPase has the greatest influence on the rate of pH decline by limiting the rate of phosphorylase and phosphofructokinase (PFK), two enzymes involved in glycolysis. England et al. (2014) proposed elevated temperatures (39-42C) increased PFK activity, an enzyme required for the conversion of fructose-6-phosphate to fructose-1,6-phosphate in the glycolysis cycle. At 4 h, PFK activity and rate of pH decline were decreased at 42C compared to
33C. Kyla-Puhju et al. (2005) reported higher temperatures (39–42°C) increased glycogen debranching enzyme activity, the enzyme responsible for removing glucose molecules from glycogen, in pork masseter and longissimus dorsi muscles. By increasing glycogen debranching enzyme activity, additional substrate is available to allow glycolysis to proceed. These studies demonstrate the increased rate of pH decline during postmortem metabolism is the result of a combination of enzymes that are influenced by high temperatures.
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Chilling carcasses too quickly results in the phenomenon of cold shortening
(Locker and Hagyard, 1963), which occurs when carcasses reach 14C to 19C prior to the depletion of ATP (Locker and Hagyard, 1963). Elevated temperatures during postmortem chilling can cause heat shortening which results in shortened sarcomeres
(Marsh, 1954; Hertzman et al., 1993). Locker and Hagyard (1963) reported increased sarcomere lengths in carcasses held at 25°C for 1.5 to 11 h prior to chilling at 2°C compared to carcasses constantly chilled at 2°C. It is now believed the loss of proteolytic enzyme functionality during postmortem aging is the primary reason for the observed decrease in tenderization, not the degree of sarcomere shortening (Locker and Hagyard,
1963; Kim et al., 2012).
Postmortem aging is important to the tenderization process, but tenderization can be influenced by increased carcass temperatures during chilling. Lochner et al. (1980) investigated the effects of slow chilling on the tenderness of lean and fat carcasses. The authors concluded that temperatures at 2–4 h were most important to tenderization but offered no mechanism. Koohmaraie (1992) reported an increase in calpain-1 autolysis at lower pH values and higher temperatures. This could cause limited proteolysis and increased toughness of meat products. Marsh et al. (1981) investigated the effects of temperature on beef tenderness in the longissimus muscle. All carcasses were subjected to a 3 h chilling period at 37° C prior to chilling at 2°C. Carcasses with a higher pH at 3 h postmortem had improved tenderness. The authors suggested a high pH in combination with high temperature promotes the activation of enzymes responsible for postmortem protein degradation, but analysis of tenderization throughout aging was not conducted.
Within the semimembranosus pH decline and temperature have been reported to vary
21 between the deep and superficial portions of the muscle, with the deep semimembranosus having a higher temperature, more rapid pH decline, and decreased proteolysis after 7 d of aging (Kim et al., 2010). Similar results were observed in beef longissimus lumborum muscles resulting in increased WBSF values (Kim et al., 2012). Additional work by
Mohrhauser et al. (2014) found allowing carcasses to remain at elevated temperatures prior to being chilled, did not impact tenderness or proteolysis when evaluating the calpain system under different pH and temperature conditions. However, the authors did note temperature had a larger effect on postmortem tenderization than the rate of pH decline.
Color is one attribute beef consumers use to determine product quality.
Consumers prefer beef to be bright cherry red, while pale or discolored product is often discounted or discarded (Young et al., 1999). Muscles entering rigor at higher temperatures have been reported to have higher L* values and decreased color stability than carcasses entering rigor at normal temperatures. Young et al. (1999) reported that during the first hour of blooming, steaks from the longissimus lumborum muscle that entered rigor at 24°C had increased L* values compared to muscles that entered rigor at
9°C or 14°C. Kim et al. (2010) assessed color of the deep and superficial portions of beef semimembranosus muscles for 7 d. On average, the deep portion of the semimembranosus was lighter, redder, and yellower than the superficial portion of the semimembranosus. In the sternomandibularis, Hughes et al. (2018) reported muscles entering rigor at 35°C were lighter than muscles entering rigor at 5°C and 15°C.
Increased color values are due to changes in the redox capabilities of myoglobin caused by high temperature and low pH conditions; a more open myofibril structure caused by
22 myofibril shrinkage that allows for more water to move to the surface, and increased light scattering and reflectance (Kim et al., 2010; Hughes et al., 2018).
Postmortem chilling temperatures also impact color stability of beef muscles.
Young et al. (1999) reported longissimus lumborum muscles entering rigor at 24C had higher a* values through the first week of storage, but after two weeks, the muscles that entered rigor at 9C or 14C had higher L* and a* values. Sammel et al. (2002) reported the effects of temperature on color of cold-boned (fabricated after rigor) and hot-boned
(fabricated prior to rigor) of the inside and outside semimembranosus. The cold-boned inside semimembranosus had the highest temperatures during chilling and were the lightest at d 0 of display. By the end of the 5-d display period, the cold-boned inside semimembranosus was dark red to brown and no longer an acceptable color. In comparison, the outer semimembranosus and hot-boned inner semimembranosus maintained acceptable color throughout the 5-d display period. Muscles entering rigor at a higher temperature have been reported to become reflective earlier, partially due to the observed decreased fiber width and modified sarcoplasmic protein structures (i.e. denaturation) of muscles entering rigor at increased temperatures (Young et al., 1999;
Hughes et al., 2018). High temperatures increase the rate of pH decline, and lower pH results in a shrinkage of the myofilament lattice structure (Hughes et al., 2017). Other possibilities for poor color stability are myoglobin denaturation from high temperature and low pH during rigor, less oxygen consumption to maintain oxymyoglobin, and lower metmyoglobin reducing activity as a result of high temperature/low pH postmortem conditions (Sammel et al., 2002).
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Sensory attributes of beef products may also be affected by carcass temperatures.
Warner et al. (2014) assessed consumer ratings of beef longissimus lumborum and gluteus medius and reported higher scores for muscles with decreased temperatures at pH
6. Aroma may also be affected by muscles held at increased temperatures as demonstrated by Locker and Daines (1975) in beef sternomandibularis, which the authors attributed to bacterial growth from the increased temperatures. The effect of high temperatures on flavor profile and odors in beef requires further research to better understand the mechanisms involved.
Problem
The demand for beef products is increasing in the United States and globally as consumers seek the flavor profile and nutritional quality of beef. Due to the increasing demand for beef as a quality protein source and limited slaughter capacity of beef plants, packers are seeking to increase carcass weight per trolley to maximize throughput.
Additionally, as packers continue to raise the ceiling for discounts for HCW, cattle producers are selling larger cattle to maximize profits. Previous studies report heavier carcasses have higher internal temperatures during chilling (Agbeniga and Webb, 2018;
Djimsa et al., 2019; Fevold et al., 2019; Lancaster et al., 2020). Additionally, heavier carcasses are generally fatter and higher grading carcasses. In an early study by Lochner et al. (1980), the heavy, higher grading beef carcasses had slower chilling rates. In addition to subcutaneous fat acting as an insulator the authors postulated intramuscular fat may also insulate the carcass, increasing carcass temperatures and extend chilling time. This increase in chilling time may lead to the development of quality issues,
24 including increased water loss, decreased protein degradation and tenderization, and poor color. With some muscles being utilized for further processed products, it is important to understand the effects of heavier HCW on product quality to continue producing high- quality fresh and processed beef products.
Objectives
Internal temperatures recorded in most previous studies are subsurface or a few centimeters beneath the surface. The studies in this dissertation aimed to evaluate internal temperature decline of three primals at depths up to 20 cm. The first objective of this dissertation was to determine the influence of HCW and quality grade on internal temperature decline of the chuck, loin, and round. The second objective was to determine the influence of HCW on internal temperature decline, ultimate pH, color, and sarcomere length of the serratus ventralis, longissimus lumborum, and semitendinosus in USDA
Select and low Choice carcasses. The third objective was to determine the effect of HCW on WBSF, cook loss, and troponin-T and desmin degradation of the serratus ventralis, longissimus lumborum, and semitendinosus in USDA Select and low Choice carcasses aged 5, 10, or 14 days. The final objective was to utilize consumer sensory panels to determine the effect of HCW on palatability traits and consumer liking of Denver cut, strip loin, and eye of round steaks in USDA Select and low Choice carcasses aged 5, 10, or 14 days.
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Strydom, P. E., L. Frylinck, J. L. Montgomery, and M. F. Smith. 2009. The comparison of three beta-agonists for growth performance, carcass characteristics and meat quality of feedlot cattle. Meat Sci. 81(3):557-564. doi: 10.1016/j.meatsci.2008.10.011 Taylor, R. G., G. H. Geesink, V. F. Thompson, M. Koohmaraie, and D. E. Goll 1995. Is z-disk degradation responsible for postmortem tenderization? J. Anim. Sci. 73(5):1351-1367. doi: 10.2527/1995.7351351x United States Department of Agriculture, Agricultural Marketing Service (USDA-AMS). 2021. Beef grading shields. https://www.ams.usda.gov/grades- standards/beef/shields-and-marbling-pictures (Accessed 26 March 2021). United States Department of Agriculture, Economic Research Service (USDA-ERS). 2019. Livestock and Poultry Live and Dressed Weights. https://www.ers.usda.gov /data-products/livestock-meat-domestic-data/livestock-meat-domesticdata/ #Livestock%20and%20poultry%20live%20and%20dressed%20weights. Warner, R. D., J. M. Thompson, R. Polkinghorne, D. Gutzke, and G. A. Kearney. 2014. A consumer sensory study of the influence of rigor temperature on eating quality and ageing potential of beef striploin and rump. Anim. Prod. Sci. 54(4):396-406. doi: 10.1071/an12226 Wheeler, T. L., and M. Koohmaraie. 1994. Prerigor and postrigor changes in tenderness of ovine longissimus muscle. J. Anim. Sci. 72(5):1232-1238. doi: 10.2527/1994.7251232x Wheeler, T. L., S. D. Shackelford, and M. Koohmaraie. 2007. Beef longissimus slice shear force measurement among steak locations and institutions. J. Anim. Sci. 85(9):2283-2289. doi: 10.2527/jas.2006-736 Whipple, G., and M. Koohmaraie. 1991. Degradation of myofibrillar proteins by extractable lysosomal enzymes and m-calpain, and the effects of zinc chloride. J. Anim. Sci. 69(11):4449-4460. doi: 10.2527/1991.69114449x White, A., A. O'Sullivan, D. J. Troy, and E. E. O'Neill. 2006. Manipulation of the pre- rigor glycolytic behavior of bovine M. longissimus dorsi in order to identify causes of inconsistencies in tenderness. Meat Sci. 73(1):151-156. doi: 10.1016/j.meatsci.2005.11.021 Wilson, D. E., G. H. Rouse, and S. Greiner. 1999. Relationship between chemical percentage intramuscular fat and USDA marbling score, Iowa State University. Young, O. A., A. Priolo, N. J. Simmons, and J. West. 1999. Effects of rigor attainment temperature on meat blooming and colour on display. Meat Sci. 52(1):47-56. doi: 10.1016/s0309-1740(98)00147-8 Yu, L. P., and Y. B. Lee. 1986. Effects of postmortem pH and temperature on bovine muscle structure and meat tenderness. J. Food Sci. 51(3):774-780. doi: 10.1111/j.1365-2621.1986.tb13931.x
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Chapter 2
Beef hot carcass weight and quality grade influence internal carcass temperature decline
33
Abstract
Beef hot carcass weights (HCW) in the United States have increased more than 70 kg in the last 30 years. Simultaneously, the beef industry has seen an improvement in carcass quality grades (QG). Heavier and higher grading carcasses may result in chilling inefficiencies. The objective of this study was to investigate the influence of beef HCW and QG on internal temperature decline during chilling of the chuck, loin, and round. A- maturity beef carcasses (<30 months; n = 309) were selected at a commercial beef packing facility by weight [light (LW) = 296–341 kg; middle (MW) = 386–432 kg; heavy
(HW) = 466–523 kg]. A 20 cm data logger was placed in the chuck and round and a 10 cm data logger placed in the loin to record internal temperature for 26 h during chilling.
A QG HCW interaction was observed for internal temperature in the chuck (P = 0.02) and round (P < 0.0001). Generally, as HCW and QG increased, internal carcass temperature was higher. In the loin, heavy weight carcasses had higher temperatures (P <
0.0001) during chilling. USDA Select carcasses had decreased temperatures compared to low Choice and upper 2/3 Choice carcasses. All loins were 3.5–4.0C at 26 h of chilling.
The internal temperature of chucks at 26 h was 6.1–7.7C in all LW, Select MW, and LC
MW carcasses, 9.1–9.5C in UC MW and Prime MW carcasses, and 10.7–11.6C in all
HW carcasses (P < 0.05). Round temperatures at 26 h were 8.9–10.6C in LW carcasses,
11.8–12.7C in MW carcasses, and 14.3–14.8C in HW carcasses. These data suggest internal temperature decline of some beef primals is impacted by HCW and QG during the chilling of beef carcasses. Generally, heavier carcasses with improved QG retain heat for an extended period of time. Additional research to further explore the interaction of
HCW and QG will help improve chilling systems and efficiency for the beef industry.
34
Introduction
Hot carcass weight (HCW) of fed cattle has increased an average of 2.3 kg per year since the early 1990s (USDA-ERS, 2019). During this time frame, average backfat thickness for carcasses has remained approximately 1.27 cm, while intramuscular fat has increased, resulting in improved quality grades (QG; NCBA, 2016). In the early 1990s,
55% of carcasses graded USDA Choice or Prime, compared to 70% in 2016 (NCBA,
2016). These changes to muscle and fat deposition of fed cattle can be attributed to better understanding of diet (Bruns et al., 2004), utilization of beta agonists and other growth promoting agents to promote lean tissue growth (Ebarb et al., 2016), and improved genetics and breeding selections for carcass characteristics. Despite the steady increase in
HCW, the distribution of carcass weights varies greatly based upon several factors including, but not limited to, genetics, sex, days on feed, and seasonality of feeding and marketing (Marchello et al., 1970; Martin et al., 1971; Park et al., 2002; Wheeler et al.,
2005; Choat et al., 2006).
Increased HCW can benefit beef producers as it allows producers to maximize profits when marketing cattle. Beef packing facilities can benefit from heavier carcasses by optimizing product throughput with fewer head of cattle to meet the demand of beef consumption. Conversely, heavier carcasses pose a challenge during postmortem chilling.
Although HCW have increased, beef packers continue to use chilling systems designed when the average carcass was 285 kg (USDA-ERS, 2019). Chilling systems most commonly used in the beef industry rely on chilled air movement only (~1.7C with high-speed air movement) or chilled air movement supplemented with spray chilling
(intermittent cycles of sprayed cold water). By using both chilled air and spray chilling,
35 the beef industry is able to increase carcass chilling rates and decrease carcass temperatures (Prado and de Felício, 2010) in an effort to decrease cooler shrinkage and improve product quality (Allen et al., 1987).
The chuck, loin, and round are the largest beef primals on the carcass accounting for over 60% of total HCW (27.9%, 16.7%, and 21.7%, respectively; NCBA, 2014).
Based on the mass of the chuck and round, it is expected these primals would have a decreased chilling efficiency under normal chilling procedures compared to smaller primals. Subcutaneous fat has been well documented to slow chilling by acting as an insulator and increasing heat retention (Smith et al., 1976; Lochner et al., 1980; Aalhus et al., 2001). It has been suggested intramuscular fat may have insulation properties like subcutaneous fat (Lochner et al., 1980), but these studies are limited. Thus, the relationship between intramuscular fat and internal carcass temperature remains unclear.
Chilling systems account for approximately 24.5% of the total electricity costs, making refrigeration the largest energy cost to packing facilities (Li et al., 2018).
Developing a greater understanding of the chilling dynamics of heavier carcasses could result improved chilling efficiency of these carcasses and decreased energy costs. There is limited research evaluating the effects of HCW and QG on internal carcass temperature during chilling. It was hypothesized that increased HCW and improved QG would result in carcasses with higher internal temperatures during chilling. Therefore, the objective of this study was to determine the influence of beef HCW and QG on internal temperature decline of the chuck, loin, and round.
36
Materials and Methods
Carcass Selection and Internal Temperature Monitoring
Institutional Animal Care and Use Committee approval was not obtained as cattle were humanely harvested at a USDA inspected commercial beef packing facility in the upper Midwest. Thirty-five carcasses were selected per day over nine days from June to
September 2018. A total of 309 A-maturity (<30 months) beef carcasses produced usable data. Approximately an equal number of carcasses were selected based upon weight
[light (LW) = 296–341 kg; middle (MW) = 386–432 kg; heavy (HW) = 466–523 kg] 45 min postmortem. A stainless-steel data logger (20.32 cm; ThermoWorks, American Fork,
UT) was placed in the center of the round near, but not touching, the femur 48 min postmortem (Figure 2.1a). Another 20.32 cm data logger was placed in the chuck posterior to the scapula at the junction of the brisket and foreleg in the serratus ventralis
50 min postmortem (Figure 2.1b). A 10.16 cm data logger was placed in the geometric center of the longissimus lumborum at the third lumbar vertebra 50 min postmortem
(Figure 2.1c). Carcasses entered a chilling cooler belonging to one of five cooler styles
(determined by the direction of airflow) at the plant and internal temperature (C) was recorded every 15 minutes in the right side of the carcass for the duration of the chilling period (26 h). During chilling, carcasses were subjected to continual air movement and intermittent spray chilling (80 s every 32 min for the first 20 h).
At 26 h postmortem, carcasses were ribbed and allowed to bloom for 20 min.
Marbling score, QG, ribeye area, and 12th rib back fat thickness were collected on the right side of the carcass by trained South Dakota State University personnel. Quality
37 grade was determined by in-plant dentition and marbling score of SDSU personnel. Yield grade was calculated using the following equation:
푌푖푒푙푑 퐺푟푎푑푒 = 2.50 + (2.50 × Fat Thickness, inches)
− (0.32 × Ribeye Area, in2)
+ 0.20 × % Kidney, Pelvic, and Heart Fat)
+ (0.0038 HCW, lbs)
Carcasses were categorized by HCW and QG [USDA Select, low Choice (LC), upper 2/3
Choice (UC), and Prime]. Following grading, data loggers were removed and temperatures downloaded using ThermaData Studio software (v. 3.3.0.0; ThermoWorks,
American Fork, UT). Data logger malfunction during chilling resulted in the removal of one carcass from the temperature analysis of the chuck, one from the loin analysis, and six from the round analysis.
Statistical Analysis
For this study, carcass side was considered the experimental unit. Carcass traits were analyzed for the effects of HCW and QG using the MIXED procedure of SAS (v
9.4; SAS Inc., Cary, NC). Internal temperature data were analyzed as repeated measures using the Toeplitz covariance structure in the MIXED procedure to determine the effects of HCW, QG, and their interactions. Backfat thickness at the 12th rib was included as a covariate; collection day and cooler style were included as random effects. Separation of least square means was performed using a Tukey-Kramer adjustment at = 0.05.
38
Results
Carcass Traits
Carcass traits (Table 2.1) of the 309 carcasses monitored indicate the normal variation that is observed in an upper Midwest beef plant. Carcasses had no dairy influence or hump (rhomboideus <5.1 cm), were grain-finished, and <30 months of age.
No dark cutting carcasses were observed in the carcasses monitored.
The weight ranges of carcasses collected were 297-341 kg, 386-431 kg, and 466-
526 kg for LW, MW, and HW carcasses, respectively. As HCW increased, ribeye area and backfat increased. The overall QG distribution of carcasses monitored was 21.4%
Select, 35.3% LC, 37.8% UC, and 5.5% Prime. Within each weight group, LW carcasses had the highest percentage of Select carcasses and HW carcasses had the lowest percentage of Select carcasses. Backfat and yield grade increased as marbling score and
QG improved.
Temperature decline
In the chuck, a QG HCW interaction was observed for internal temperature decline (P = 0.02; Figure 2.2). At 0 h, the temperature of chucks from LC HW carcasses
(40.1 ± 0.6C) was higher than LC LW (38.5 ± 0.6C; P = 0.04), LC MW (38.3 ± 0.5C;
P = 0.01), and Select MW carcasses (38.2 ± 0.6C; P = 0.03). By 6 h of chilling, all LW carcasses had lower temperatures than HW carcasses. During chilling, chucks from
Select LW, LC LW, Select MW, and LC MW carcasses had similar chilling dynamics. At
26 h of chilling, chucks across all QG in LW, Select MW, and LC MW carcasses had the lowest temperatures (6.1–7.7C), followed by UC MW and Prime MW (9.1–9.5C), and
HW carcasses across all QG had the highest temperatures (10.7–11.6C).
39
In the round, a QG HCW interaction was observed (P < 0.0001; Figure 2.3). At
0 h, rounds from LC LW carcasses (40.4 ± 0.3C; P = 0.01) had higher temperatures compared to Select LW (39.6 ± 0.3C; P = 0.01) and Prime LW carcasses (39.1 ± 0.5C;
P = 0.01). Rounds from Select MW carcasses (40.8 ± 0.3C; P < 0.01) were intermediate to Select LW (39.6 ± 0.3C; P < 0.01) and UC MW (39.9 ± 0.2C; P = 0.03) carcasses.
Low Choice MW carcasses (40.4 ± 0.3C; P = 0.02) had higher temperatures compared to Select LW (39.6 ± 0.3C; P = 0.02) and Prime LW carcasses (39.1 ± 0.5C; P = 0.02).
Internal temperature of rounds from LW carcasses peaked between 1.5–1.75 h of chilling, increasing 0.5–0.8C from the 0 h temperature. Rounds from MW and HW carcasses increased 0.8–1.2C from the 0 h temperature and peak temperatures were recorded between 2–3 h of chilling. At 12.75 h of chilling, rounds from Select HW carcasses (27.6
± 0.4C) had higher temperatures than UC HW carcasses (26.7 ± 0.2C; P = 0.04). After an additional 1.5 h of chilling, Select HW and UC HW carcasses had similar temperatures. At 26 h, Select LW carcasses had similar temperatures (8.9 ± 0.3C) to
Prime LW carcasses (9.2 ± 0.5C; P = 0.55); Prime LW carcasses had similar temperatures (9.2 ± 0.5C) to UC LW carcasses (9.9 ± 0.3C; P = 0.28); and UC LW (9.9
± 0.3C) and LC LW (10.6 ± 0.3C) had similar temperatures (P = 0.05). At 26 h, similar temperatures were observed between UC MW (11.8 ± 0.2C), Prime MW (12.2 ± 0.6C), and LC MW carcasses (12.5 ± 0.3C; P > 0.05). Prime MW (12.2 ± 0.6C), LC MW
(12.5 ± 0.3C), and Select MW carcasses (12.7 ± 0.3C; P > 0.05) had similar temperatures at 26 h. Select MW carcasses had similar temperatures (12.7 ± 0.3C) to
Prime HW carcasses (14.3 ± 0.8C; P = 0.06) at 26 h. All HW carcasses were of similar
40 temperatures at 26 h (Prime HW = 14.3 ± 0.8C, UC HW = 14.5 ± 0.2C, LC HW = 14.6
± 0.3C, and Select HW = 14.8 ± 0.4C; P > 0.05).
No QG × HCW interaction was observed for internal temperature in the loin.
Internal temperature decline of the loin was influenced by HCW (P < 0.0001; Figure
2.4a). By 0.75 h of chilling, loins from LW carcasses exhibited decreased temperatures
(37.9 ± 0.2C) compared to MW (39.0 ± 0.2C; P < 0.0001) and HW carcasses (38.8 ±
0.2C; P = 0.01). Loins from MW carcasses remained at similar temperatures to HW until 2.25 h of chilling. By 15.75 h, temperatures of loins from HW were similar to MW, and all loins were the same temperature (4.2–4.8C) by 22.5 h of chilling.
Temperature decline of the loin was also influenced by QG (P = 0.04; Figure
2.4b). After 1.5 h of chilling, Select loins had lower temperatures (P = 0.03) compared to
UC loins. After 4.25 h, Select loins had lower temperatures compared to LC loins (P =
0.04). By 18.75 h, no differences were observed in the loin for internal temperature based upon QG (5.4–6.1C).
Discussion
The influence of HCW on internal temperature decline is an area of interest to the beef industry (Aalhus et al., 2001; Agbeniga and Webb, 2018; Djimsa et al., 2019).
Existing chilling systems may not sufficiently chill heavier carcasses currently produced in the beef industry. This study supports previous work reporting increased internal carcass temperature during postmortem chilling as carcass weight increases. Differences in internal temperature decline have been reported in lighter carcasses (< 300 kg) in other countries. Agbeniga and Webb (2018) reported a slower rate of temperature decline in the
41 loin from carcasses ≥290 kg compared to carcasses weighing ≤260 kg in the first 24 h of chilling. In the U. S., the average beef carcass is much heavier (~384 kg; USDA-ERS,
2019). Djimsa et al. (2019) assessed the temperature decline of beef loins and rounds and reported heavy carcasses (greater than the plant average) maintained higher temperatures and had decreased rates of temperature decline compared to light carcasses (lower than the plant average). Similar results were reported by Fevold et al. (2019) in beef longissimus and semimembranosus muscles from light (<363 kg), middle (363–408 kg), and heavy (>408 kg) carcasses and by Lancaster et al. (2020) in beef semimembranosus muscles from average weight (335-387 kg) and oversized (≥432 kg) carcasses.
Elevated internal temperatures observed in heavier carcasses can be a result of increased heat retention caused by the combination of muscle mass, muscle location
(Sammel et al., 2002; Lancaster et al., 2020), heat generation during postmortem metabolism (de Meis, 1998; Scheffler and Gerrard, 2007), and adipose tissue (Aalhus et al., 2001). As muscles increase in size and mass, the rate of heat dissipation is slowed, causing larger muscles to remain at higher temperatures for extended periods of time
(Savell, 2012). This concept can be applied to primals such as the round and chuck.
Larger primals maintain higher temperatures for a longer duration during chilling. In the current study, as HCW increased, peak temperatures in the round occurred later during chilling and at higher temperatures. Superficial portions of muscles are able to dissipate heat at a faster rate than deep muscles as demonstrated by Sammel et al. (2002) and
Lancaster et al. (2020) in the semimembranosus. During the conversion of muscle to meat, as muscles work to maintain normal function and homeostasis, heat is generated through muscle contractions and glycolysis. The majority of heat generated during
42 postmortem metabolism derives from two sources: 1) hydrolysis of ATP to ADP and 2) inorganic phosphate and during glycolysis as glucose is converted to pyruvate (de Meis,
1998; Scheffler and Gerrard, 2007). The hydrolysis of ATP results in the release of 52 kJ/mol of heat, which can raise the temperature of muscle up to 2.2°C (Morley, 1974).
Subcutaneous fat also acts as an insulator, allowing heat retention during the postmortem chilling process (Koohmaraie et al., 1988; Aalhus et al., 2001). Lochner et al.
(1980) suggested intramuscular fat may also act in a similar capacity during postmortem chilling. In the current study, internal temperature during chilling varied with increasing levels of intramuscular fat (determined by marbling score). In the round, lower QG carcasses had higher temperatures compared to higher QG carcasses periodically throughout chilling. In the chuck, Select LW carcasses had decreased temperatures compared to Prime LW carcasses. Contrary to these observations, loins from Select MW and Select HW carcasses had higher temperatures compared to their Prime counterparts.
The influence of intramuscular fat on postmortem temperature remains uncertain and is variable with muscle and carcass size.
Interestingly, loins from HW carcasses had a lower temperature compared to MW at 0 h, but by 0.5 h, loins from MW and HW carcasses were of similar temperatures. This demonstrates the ability of heavier carcasses to retain heat, while lighter carcasses are able to dissipate heat more rapidly. Despite the influence of HCW on internal temperature, loins in each weight group achieved similar internal temperatures prior to presentation for grading (3.5–4.0°C). As required by USDA, loin temperature must achieve ≤4.4℃ prior to ribbing for uniformity at grading (USDA-AMS, 2019). Loins that do not reach ≤4.4℃ may receive a lower QG at the time of grading (Calkins et al., 1980).
43
Heavier carcasses create increases in heat load in chilling coolers. Many plants allot additional chilling time to allow the entire carcass to reach 4C prior to fabrication.
Some beef plants opt to fabricate at approximately 24 h or use solid carbon dioxide to increase the rate of chilling in fabricated subprimals. Other options to combat the increased heat load in coolers include increasing air speeds, increasing the amount and frequency of chilled water applied to the carcass surface, and increasing carcass spacing to increase air movement around carcasses. Changes in cooler operation through carcass spacing or modified chilling regimens would likely increase plant cost or result in decreased processing efficiencies.
The decreased chilling rate observed in heavier beef carcasses could indicate current chilling systems may not be sufficient if HCW continues to increase. The energy required to chill a carcass from body temperature (39.5C) to chilled temperature (2.0C) can be measured using British thermal units (BTUs). Using the current chilling systems, the energy required to chill LW carcasses would be approximately 32,800 BTU, while
HW carcasses would require approximately 48,100 BTU. This 31.8% increase in energy required to chill HW carcasses coupled with a higher temperature for longer periods of time suggests current chilling systems are not as efficient at chilling heavier carcasses in comparison to lighter carcasses. Studies have assessed the effects and cost of very rapid chilling procedures (VRC; -40C with rapid air movement) on beef carcasses to help chill larger primals and carcasses more efficiently (Aalhus et al., 2001; Bowater, 2001; Van
Moeseke et al., 2001). In the European Union, Bowater (2001), concluded VRC may be a cost-effective alternative to normal plant procedures based upon cost and revenue. Very rapid chilling can result in increased product throughput; however, with VRC, darker
44 product color and increased drip loss during storage has been observed, decreasing product quality (Bowling et al., 1987; Aalhus et al., 2002). Additional research is required to determine if an optimum time-temperature combination exists for VRC so as to increase production efficiency while minimizing product quality issues.
Conclusion
Chilling heavier carcasses efficiently will remain a challenge for the beef industry as carcass weight and composition change. Heavier HCW increased the initial temperature and extended the amount of time at higher temperatures. The effect of QG on temperature decline was variable with muscle and HCW. In the current study, Select MW and LC MW carcasses exhibited chilling dynamics more closely aligned to LW carcasses, while UC MW and Prime MW carcasses exhibited chilling dynamics more closely aligned to HW carcasses. Understanding the role of intramuscular fat on postmortem chilling of beef carcasses will help clarify the relationship between HCW,
QG, and internal carcass temperatures.
45
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size on chilling rate, pH decline, display color, and tenderness of top round subprimals. Trans. Anim. Sci. 4(4):2573-2102. doi: 10.1093/tas/txaa199 %1 txaa199 Li, S., R. M. M. Ziara, B. Dvorak, and J. Subbiah. 2018. Assessment of water and energy use at process level in the U.S. beef packing industry: Case study in a typical U.S. large‐size plant. J. Food Process Eng. 41(8):e12919. doi: 10.1111/jfpe.12919 Lochner, J. V., R. G. Kauffman, and B. B. Marsh. 1980. Early-postmortem cooling rate and beef tenderness. Meat Sci. 4(3):227-241. doi: 10.1016/0309-1740(80)90051-0 Marchello, J. A., D. E. Ray, and W. H. Hale. 1970. Carcass characteristics of beef cattle as influenced by season, sex and hormonal growth stimulants. J. Anim. Sci. 31(4):690-696. doi: 10.2527/jas1970.314690x Martin, A. H., H. T. Fredeen, and G. M. Weiss. 1971. Characteristics of youthful beef carcasses in relation to weight, age and sex: III. Meat quality attributes. Can. J. Anim. Sci. 51(2):305-315. doi: 10.4141/cjas71-043 Morley, M. J. 1974. Measurement of the heat production in beef muscle during rigor mortis. Int. J. Food Sci. Tech. 9(2):149-156. doi: 10.1111/j.1365- 2621.1974.tb01758.x National Cattlemen’s Beef Association (NCBA). 2014. Beef cutout calculator. https://www.beefresearch.org/CMDocs/BeefResearch/Beef%20Cutout%20Calcul ator.pdf (Accessed September 1, 2019). National Cattlemen’s Beef Association (NCBA). 2016. Beef quality audit. https://www.bqa.org/Media/BQA/Docs/2016nbqa_es.pdf (Accessed July 12 2019). Park, G. B., S. S. Moon, Y. D. Ko, J. K. Ha, J. G. Lee, H. H. Chang, and S. T. Joo. 2002. Influence of slaughter weight and sex on yield and quality grades of Hanwoo (Korean native cattle) carcasses. J. Anim. Sci. 80(1):129-136. doi: 10.2527/2002.801129x Prado, C. S., and P. E. de Felício. 2010. Effects of chilling rate and spray-chilling on weight loss and tenderness in beef strip loin steaks. Meat Sci. 86(2):430-435. doi: 10.1016/j.meatsci.2010.05.029 Sammel, L. M., M. C. Hunt, D. H. Kropf, K. A. Hachmeister, C. L. Kastner, and D. E. Johnson. 2002. Influence of chemical characteristics of beef inside and outside semimembranosus on color traits. J. Food Sci. 67(4):1323-1330. doi: 10.1111/j.1365-2621.2002.tb10282.x Savell, J. W. 2012. Beef carcass chilling: Current understanding, future challenges. National Cattlemen's Beef Association, Centennial, CO. Scheffler, T. L., and D. E. Gerrard. 2007. Mechanisms controlling pork quality development: The biochemistry controlling postmortem energy metabolism. Meat Sci. 77(1):7-16. doi: 10.1016/j.meatsci.2007.04.024 Smith, G. C., T. R. Dutson, R. L. Hostetler, and Z. L. Carpenter. 1976. Fatness, rate of chilling and tenderness of lamb. J. Food Sci. 41(4):748-756. doi: 10.1111/j.1365- 2621.1976.tb00717_41_4.x United States Department of Agriculture, Agricultural Marketin Service (USDA-AMS). 2019. QAD Procedure 500: Beef, bullock, and bull grading methods and procedures. Agricultural Marketing Service, Washington, DC.
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Table 2.1 Carcass traits (means ± SE) of beef carcasses by grade within weight group
LW1 MW1 HW1 Quality Average grade2 Se LC UC Pr Se LC UC Pr Se LC UC Pr SE n 27 33 25 6 23 32 36 6 16 44 56 5 – %3 29.7 36.3 27.5 6.5 23.7 33.0 37.1 6.2 13.2 36.4 46.3 4.1 – HCW, kg 330c 325c 325c 329c 407b 408b 406b 410b 480a 486a 484a 488a 3.5 REA, cm2 82.7gh 85.1fh 78.6eg 73.9e 96.7d 91.9bc 89.2bf 86.3bgh 107.3a 103.6a 99.8d 100.3acd 2.2 Marbling4 354e 454d 548c 735b 361e 438d 567a 745b 374e 445d 576a 742b 8.8 Backfat5, cm 1.0f 1.2df 1.4ce 1.7bce 1.2df 1.3de 1.6ac 1.6bce 1.4cde 1.7ab 1.8ab 1.7bce 0.1 Yield grade 2.5f 2.6f 3.1bcd 3.7ace 2.6f 3.1be 3.5ce 3.6acde 2.9bdf 3.5a 3.8a 3.7ade 0.2 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice; UC = upper 2/3 Choice; and Pr = Prime 3Reported as a percent of the total carcasses in the corresponding weight group 4Marbling scores are as follows: 300 = Slight; 400 = Small; 500 = Modest; 600 = Moderate; 700 = Slightly Abundant 5Backfat was measured between the 12th and 13th ribs following ribbing a-h Means with different superscripts within a row differ (P < 0.05)
48
49
Figure 2.1 Data logger location in the a) round, b) chuck, and c) loin
A)
B)
C)
Figure 2.2 Interaction of hot carcass weight1 and quality grade2 for internal temperature decline of chuck primals of beef carcasses (n=308)
42 P = 0.02 Se LW LC LW UC LW Pr LW Se MW LC MW UC MW Pr MW Se HW LC HW UC HW Pr HW 36
30
C)
°
( 3 24
18 Temperature
12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice; UC = upper 2/3 Choice; Pr = Prime 3Temperature data loggers (20.32 cm in length) were placed in the chuck posterior to the scapula at the junction of the brisket and
foreleg in the serratus ventralis 50 min postmortem and temperature reported every 15 min 50
Figure 2.3 Interaction of hot carcass weight1 and quality grade2 for internal temperature decline of round primals of beef carcasses (n = 303)
42 P < 0.0001 Se LW LC LW UC LW Pr LW Se MW LC MW UC MW Pr MW Se HW LC HW UC HW Pr HW 36
30
C)
°
( 3
24
Temperature 18
12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice; UC = upper 2/3 Choice; Pr = Prime 3Temperature data loggers (20.32 cm in length) were placed in the center of the round near, but not touching, the femur 48 min
postmortem and temperature reported every 15 min 51
Figure 2.4 Internal temperature decline of loin primals of beef carcasses (n = 308). Data are reported by a) weight group1 and b) quality grade2 42 P < 0.0001 A LW MW HW
36
30
C)
(
3 24
18 Temperature 12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
52
42 B P = 0.04 Se LC UC Pr
36
30
C) ° 24
18 Temperature ( Temperature 12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice; UC = upper 2/3 Choice; Pr = Prime 3Temperature data loggers (10.16 cm in length) were placed in the geometric center of the longissimus lumborum at the third lumbar vertebra 50 min postmortem and temperature reported every 15 min
53
54
Chapter 3
Beef hot carcass weight influences temperature decline during chilling, color, and sarcomere length of muscles from USDA Select and low Choice carcasses
55
Abstract
An increase in hot carcass weight (HCW) has been observed in the U.S. beef industry. The objectives of this study were to assess the impact of beef HCW on: 1) internal temperature decline of the chuck, loin, and round and 2) ultimate pH (pHu), instrumental color (Hunter L, a, and b), and sarcomere length of the serratus ventralis, longissimus lumborum, and semitendinosus in USDA Select and low Choice (LC) carcasses. Carcasses were selected by HCW (light = 296–341 kg; middle = 386–432 kg; heavy = 466–523 kg) and data loggers placed in the chuck, loin, and round to record internal temperature for 26 h during chilling. Following chilling and carcass data collection, muscles from a sub-sample of Select and LC carcasses were collected for analysis. Steaks from the collected muscles were analyzed for color and sarcomere length. Heavy weight carcasses had higher internal temperature during chilling and steaks had higher L, a, and b values compared to light weight carcasses in all muscles (P <
0.001). Middle weight carcasses had similar chilling dynamics and color to both light and heavy carcasses depending on muscle. In the longissimus lumborum, steaks from LC light weight carcasses had shorter sarcomeres than steaks from Select light weight (P = 0.03) and LC middle weight carcasses (P = 0.01), but did not differ from steaks from Select middle, Select heavy, and LC heavy weight carcasses. In the semitendinosus, steaks from heavy carcasses had shorter sarcomeres than steaks from light and middle weight carcasses (P < 0.01). Hot carcass weight causes variation in temperature decline during postmortem chilling resulting in lighter, redder, and yellower steaks and shorter sarcomere lengths in some muscles from carcasses >465 kg.
56
Introduction
Average beef hot carcass weights (HCW) have increased from 319.5 kg in 1991 to 369.5 kg in 2019 (USDA-ERS, 2020). Additionally, 70% of carcasses graded USDA
Choice or higher in 2016 compared to 55% in 1991 (NCBA, 2016). Increasing beef HCW and improved quality grade (QG) have created challenges to efficiently chill carcasses in plants designed for smaller carcasses raising concerns over beef quality. Environment and internal carcass temperature during chilling directly impact postmortem physiological and biochemical changes and product quality (Locker and Hagyard, 1963; Sammel et al.,
2002; Kim et al., 2010. Research on the effects of high pre-rigor carcass temperatures on sarcomere length and color is inconclusive. Higher carcass temperatures during early postmortem chilling have been reported to decrease sarcomere length (Locker and
Hagyard, 1963), increase CIE L* and a* values (Kim et al., 2010) and decrease color stability through d 5 postmortem (Sammel et al., 2002). However, a rapid decline of carcass temperatures has been shown to result in decreased sarcomere length (Marsh and
Leet, 1966; Li et al., 2012) and decreased color stability (Li et al., 2012). The aforementioned studies were conducted using excised muscles from beef carcasses, lighter beef carcasses (~250 kg), or with non-bovine species; therefore, research regarding the impact of temperature decline in non-excised muscles is warranted.
Approximately 57.5% of beef sold in the U.S. is USDA Select or low Choice
(LC; USDA-AMS, 2020). Consumers purchasing Select or LC beef products may have a less desirable eating experience, depending on preference. In a comparison of Select to
LC strip steaks, Corbin et al. (2015) reported LC strip steaks were more tender, juicier, and had higher overall liking than Select steaks. In addition to steak and roast
57 consumption, Select and LC beef are used for lean meat products (i.e. beef jerky) and to mix with beef products with higher fat contents to decrease the fat percentage. In an industry challenged by inconsistencies in product quality, understanding the impact of temperature on postmortem mechanisms and product quality will help beef processing facilities produce more consistent products.
Postmortem muscle temperature decline is impacted by muscle size, muscle depth
(i.e. superficial v. deep; Sammel et al., 2002; Lancaster et al., 2020), and subcutaneous fat
(Aalhus et al., 2001). Lochner et al. (1980) suggested intramuscular fat acts similarly to subcutaneous fat by insulating muscles. Limited research has investigated the impact of intramuscular fat, especially in heavier carcasses, on internal carcass temperature during chilling and the subsequent effect on muscle color and sarcomere length. It is hypothesized that muscles from larger primals of heavier and higher grading carcasses will have increased internal temperatures during chilling and steaks from heavier carcasses will have higher L and a values and shorter sarcomere lengths compared to steaks lighter carcasses. Thus, the objectives of this study were to assess the impact of beef HCW on: 1) internal temperature decline in USDA Select and LC carcasses and 2) ultimate pH (pHu), instrumental color (Hunter L, a, b), and sarcomere length in the serratus ventralis (SV), longissimus lumborum (LL), and semitendinosus (ST) muscles of
Select and LC carcasses.
58
Materials and Methods
Carcass Selection, Internal Temperature Monitoring, and Sample Processing
Carcasses were selected at a USDA inspected beef packing facility in the Midwest between June and September 2018. A-maturity beef carcasses (n = 312) were selected at approximately 45 min postmortem based on HCW [light (LW) = 296–341 kg; middle
(MW) = 386–432 kg; heavy (HW) = 466–523 kg]. Stainless-steel data loggers were placed in the round, loin, and chuck of the right side of each carcass to monitor internal temperature. A 20.32 cm data logger (ThermoWorks, American Fork, UT) was inserted in the center of the round near, but not touching, the femur 48 min postmortem (Figure
3.1a). A second 20.32 cm data logger was placed in the chuck posterior to the scapula at the junction of the brisket and foreleg in the serratus ventralis 50 min postmortem
(Figure 3.1b). A 10.16 cm data logger was placed in the geometric center of the longissimus lumborum at the third lumbar vertebra 50 min postmortem (Figure 3.1c).
Carcasses entered one of five chilling coolers (as determined by airflow) and internal temperature (C) was recorded every 15 min for 26 h. During the 26-h chilling period, carcasses received continual air movement and intermittent spray chilling, per normal plant operation (80 s water spray every 32 min for 20 h). Approximately 26–30 h postmortem, carcasses were ribbed, allowed to bloom approximately 20 min, and carcass traits (12th rib backfat, ribeye area, and marbling score) were measured by trained South
Dakota State University (SDSU) personnel. Quality grade was determined by in-plant dentition and marbling score of SDSU personnel. Yield grade was calculated using the following equation:
59
푌푖푒푙푑 퐺푟푎푑푒 = 2.50 + (2.50 × Fat Thickness, inches)
− (0.32 × Ribeye Area, in2)
+ 0.20 × % Kidney, Pelvic, and Heart Fat)
+ (0.0038 x HCW, lbs)
Following carcass data collection, data loggers were removed and temperature data downloaded using ThermaData Studio software (v. 3.3.0.0; ThermoWorks,
American Fork, UT). One carcass was removed from the loin analysis and six from the round analysis due to data logger malfunctions during the chilling period. Following grading, the chuck roll [Institutional Meat Purchase Specification (IMPS) #116A; n =
116), strip loin (IMPS #180; n = 116), and eye of round (IMPS #171C; n=114) were collected from a sub-sample of USDA Select and LC carcasses. Carcasses selected were within the weight ranges previously described and met the marbling criteria for USDA
Select and LC as measured in the right loin. No dark cutting carcasses were collected. Of the carcasses meeting the sub-sample criteria, 56 Select carcasses and 60 LC carcasses were designated for subprimal collection and further analysis.
Subprimals were transported under refrigeration to the SDSU meat laboratory for further processing. Subprimals were trimmed of excess fat and fabricated into 2.54 cm thick steaks for instrumental color analysis and 0.64 cm thick steaks for sarcomere length determination. The SV (Figure 3.2a) was dissected along the major seam. The first steak from the dorsal side of the anterior portion was used for instrumental color analysis (steak
1). The first steak from the dorsal side of the posterior portion was used to determine sarcomere length (steak 5). The anterior face of the LL (Figure 3.2b) was removed prior
60 to steak fabrication. The most anterior steak was used for color analysis (steak 1) and the most posterior steak was used to determine sarcomere length (steak 11). The ST (Figure
3.2c) was bisected along the medial plane prior to fabricating into steaks. Starting from the point of the bisection, the first steak from the posterior half was used for color analysis (steak 7) and the most anterior portion used for sarcomere length (steak 1).
Samples for sarcomere length determination were vacuum packaged (3 mm thickness;
Koch Supplies, Riverside, MO) and frozen 5 d postmortem.
Ultimate pH and Color
Ultimate pH was measured on each subprimal in triplicate (anterior end, middle, and posterior end) using an Orion Star A221 pH meter (Thermo Scientific, Beverly, MA) and KNIpHE probe (model 9121 APWP; Orion, Thermo Scientific) prior to fabrication of steaks. The average pHu for each sample was used for statistical analysis.
Instrumental color (Hunter L, a, and b) was measured in triplicate after a 15 min bloom period using a colorimeter (Chroma Meter CR 410; Konica Minolta, Inc., Tokyo,
Japan). The colorimeter was calibrated using a standard white plate (L = 96.61, a = 0.02, and b = 1.12) using a 2 observer, 50 mm aperture, and C illuminance. The average values for color for each sample were used for statistical analysis.
Myofibril Isolation
Myofibrils were isolated according to the procedures of Weaver et al. (2008) with modifications. Briefly, 2.5 g of muscle was homogenized on medium speed in 20 mL of rigor buffer [RB; 75 mM KCl, 10 mM imidazole, 2 mM MgCl2, 2 mM ethylene glycol- bis(2-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA), and 1 mM NaN3)] for two 10
61 s bursts for the LL and ST and one 15 s burst for the SV (Model T25 DS1, IKA Works,
Inc., Wilmington, NC). Homogenized samples were brought to 35 mL using RB and centrifuged at 1,000 x g for 10 min at 4C. The supernatant was decanted, and the remaining pellet homogenized on medium speed in 20 ml of RB for the times indicated previously. Samples were brought to 35 mL using RB and centrifuged again at 1,000 x g for 10 min at 4C. The supernatant was decanted, and the remaining pellet re-suspended in 35 mL of RB by vigorously shaking. Samples were centrifuged a third time at 1,000 x g for 10 min at 4C. The supernatant was decanted, and the pellet re-suspended in 20 mL of RB, plus 20 l of 0.1 mM phenylmethylsulfonyl fluoride by shaking vigorously.
Sarcomere Length Determination
Sarcomere length was determined using the methods of Mohrhauser et al. (2011) with modifications. Myofibrils were diluted with double distilled H2O to 1:10 for SV,
1:100 for LL, and 1:50 for ST samples. A 175 l aliquot of myofibrils was immediately affixed onto microscope slides at 140 x g for 4 min at 25C (Statspin Cytofuge 2, Iris
Sample Processing, Westwood, MA). Slides were dried one hour in an oven at 37C. One hundred-fifty microliters of monoclonal anti-alpha-actinin (sarcomeric) antibody (#MA1-
22863, Thermo Fisher Scientific, Asheville, NC) diluted 1:500 with RB was placed onto each slide, and slides were incubated for one hour at 37C. Slides were rinsed twice with
RB and allowed to air dry. One hundred-fifty microliters of donkey anti-mouse fluorescein isothiocyanate conjugated secondary antibody (#715-095-150, Jackson
Immuno Research, West Grove, PA) diluted 1:100 with RB was applied to each slide and incubated for one hour at 37C. Slides were rinsed twice with RB and allowed to air dry.
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Twenty microliters of mounting media [75 mM KCl; 10 mM Tris, pH 8.5; 2 mM EGTA;
2mM MgCl2; 2 mM NaN3; 9.25 mM phenylenediamine; 75% (vol/vol) glycerol] was added to each slide and a coverslip applied. Coverslips were sealed with nail polish and dried overnight. Images were acquired using 40X magnification (BX53; Olympus,
Waltham, MA). The distance between z-disks was measured over 20 myofibrils for a total of 100 sarcomeres per sample using ImageJ2 software (Schindelin et al., 2012;
Rueden et al., 2017) and the average used for statistical analysis.
Statistical Analysis
Carcass side was used as the experimental unit in this study. Temperature data were analyzed as repeated measures using a Toeplitz covariance structure in the MIXED procedure in SAS (v 9.4; SAS Inc., Cary, NC) for the effects of HCW, QG, and their interactions. Backfat thickness at the 12th rib was included as a covariate and collection day and cooler style included as random effects. Carcass data, ultimate pH, instrumental color, and sarcomere length were analyzed using the MIXED procedure for the effects of
HCW, QG, and their interactions. Separation of the least square means was performed using a Tukey-Kramer adjustment at α = 0.05.
Results and Discussion
Carcass Characteristics
Carcass traits for the Select and LC carcasses collected for analysis are reported in
Table 3.1. Traits show the normal carcass variation of the upper Midwest cattle industry.
No carcasses were admitted into the study with dairy influence, signs of dark cutting, or a hump (rhomboideus >5.1 cm). Carcasses were also from grain-finished cattle that were
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<30 months of age. As expected, ribeye area increased as HCW increased indicating heavier carcasses were heavier muscled. Backfat also increased as HCW increased.
Interestingly, no differences were observed for yield grade between weight groups for
Select carcasses. However, for LC carcasses, yield grade increased as HCW increased.
Temperature Decline
A QG × HCW interaction was observed for internal temperature in the loin (P =
0.03; Figure 3.3). All loins started with similar temperatures between 39.5–40.2℃. After
0.75 h of chilling, loins from Select LW carcasses had lower temperatures (37.2 ± 0.4℃) compared to loins from Select MW (38.6 ± 0.4℃; P = 0.01), LC MW (38.4 ± 0.4℃; P =
0.04), Select HW (39.0 ± 0.4℃; P < 0.01), and LC HW carcasses (38.5 ± 0.4℃; P =
0.04). At 1.75 h, Select LW carcasses had lower temperatures (31.8 ± 0.4℃) compared to
LC LW carcasses (33.0 ± 0.4℃; P = 0.02). By 2.5 h, all loins from LW and MW carcasses had lower temperatures compared to loins from HW carcasses (P < 0.0001 and
P < 0.05, respectively). By 20.75 h of chilling, all loins from LW and MW carcasses were 4.4C. Loins from LC HW and Select HW carcasses reached 4.4C at 22.5 h and
24.25 h, respectively. The USDA mandates loins reach an internal temperature of 0–
4.4℃ prior to being presented for quality and yield grading (USDA-AMS, 2019) to ensure temperature uniformity across carcasses at the time of grading. Based on these data, HW carcasses may require additional chilling time if a plant is operating with a 24 h chilling cycle.
A QG × HCW interaction was observed for internal temperature in the round (P <
0.0001; Figure 3.4). At 0 h, rounds from Select LW carcasses had decreased temperatures
(39.3 ± 0.3℃) compared to rounds from LC LW (40.5 ± 0.3℃; P < 0.01), Select MW
64
(40.9 ± 0.3℃; P < 0.01), LC MW (40.4 ± 0.3℃; P < 0.01), and Select HW carcasses
(40.5 ± 0.4℃; P < 0.01). Rounds from Select LW and LC HW carcasses were not different at 0 h; however, after 0.25 h of chilling, rounds from Select LW carcasses had lower internal temperatures (39.5 ± 0.4℃) compared to rounds from LC HW carcasses
(40.5 ± 0.4℃; P = 0.04). For the remaining duration of chilling, rounds from Select LW carcasses had lower temperatures compared to rounds from other carcasses. Rounds reached peak temperatures at 1.5 h in Select LW carcasses (39.9 ± 0.3℃), 1.75 h in LC
LW (41.4 ± 0.3℃), 2 h in Select MW and LC MW (41.7 ± 0.3℃ and 41.5 ± 0.3℃, respectively), and 2.25 h in Select HW and LC HW (41.7 ± 0.4℃ and 41.3 ± 0.4℃, respectively). Following 26 h of chilling, differences in temperature between QG were observed in rounds from LW carcasses, with rounds from Select LW carcasses having lower temperatures (8.8 ± 0.3℃) compared to rounds from LC LW carcasses (10.6 ±
0.3℃; P < 0.0001). No temperature differences were observed between Select and LC carcasses in either the MW or HW carcasses throughout chilling. At the end of 26 h of chilling, rounds from Select HW and LC HW carcasses had the highest internal temperatures (14.9 ± 0.4℃ and 14.6 ± 0.4℃, respectively), followed by rounds from
Select MW and LC MW carcasses (12.6 ± 0.4℃ and 12.2 ± 0.3℃, respectively), LC LW carcasses (10.6 ± 0.3℃), then Select LC carcasses (8.8 ± 0.3℃).
No QG × HCW interaction was observed for temperature decline in the chuck. A main effect of HCW (P < 0.0001; Figure 3.5a) was observed for temperature decline in chucks. Chucks from HW carcasses had higher internal temperatures throughout chilling compared to chucks from LW and MW carcasses (P < 0.0001). At 1 h, chucks from HW carcasses (38.6 ± 0.7℃) had higher temperatures compared to MW carcasses (36.7 ±
65
0.5℃; P = 0.03). Chucks from HW carcasses had higher temperatures (38.1 ± 0.7℃) than LW chucks (36.3 ± 0.5℃; P = 0.05) at 1.5 h. No differences were observed in temperature throughout 26 h of chilling between chucks from LW and MW carcasses (P
> 0.05). After 26 h of chilling, the internal temperature of chucks from HW carcasses was
10.4 0.7C, MW carcasses was 7.6 0.5C, and LW carcasses was 7.1 0.5C. Quality grade did not influence temperature decline in the chuck (P = 0.87; Figure 3.5b).
Postmortem temperature of carcasses during the first few hours of chilling is of critical importance to product quality and has been reported to be influenced by muscle and adipose tissue mass (May et al., 1992; Aalhus et al., 2001). These data are supported by the results of previous studies demonstrating the influence of HCW on internal carcass temperature of beef longissimus lumborum (Warner et al., 2014; Agbeniga and Webb,
2018), semitendinosus (Lancaster et al., 2020), and semimembranosus muscles (Djimsa et al., 2019). In the current study, muscles in HW carcasses generally had the highest temperatures during chilling. At 26 h, temperatures of the chuck and round of HW carcasses was still high indicating larger primals take longer to chill. As mass increases, the energy required to remove heat from the carcass increases (Pentzer, 1966). British thermal units (BTUs) are a measurement of thermal energy and can be used to quantify energy required to chill a carcass by multiplying the amount of water in the carcass by the difference from body temperature (38.9°C) to being completely cooled (1.6°C). A 465 kg carcass will require approximately 48,100 BTU to chill while a 315 kg carcass will require approximately 32,800 BTU (Pentzer, 1966; Henrickson 1981).
During postmortem metabolism, muscle continues to produce ATP during glycolysis in an effort to maintain homeostasis (Morley, 1974; Chauhan and England,
66
2018). The hydrolysis of ATP releases approximately 52 kJ/mol (de Meis, 1998) and without the circulatory or respiratory systems to rid muscle of heat, muscle temperature has been reported to rise as much as 2.2°C (Morley, 1974). While larger muscles are more efficient at retaining heat, it is important to recognize heat retention is also dependent on location within muscles and within a carcass; deep muscles are unable to dissipate heat as quickly as superficial muscles (Aalhus et al., 2001; Kim et al., 2010).
Additionally, subcutaneous fat is known to insulate carcasses during postmortem chilling (Koohmaraie et al., 1988; Aalhus et al., 2001). Intramuscular fat has been suggested to act as an insulator during the chilling process by decreasing the rate of heat dissipation (Lochner et al., 1980). However, the role of intramuscular fat during chilling of beef carcasses remains unclear. In the current study, temperatures in the round and the loin were influenced by QG. Select LW carcasses exhibited lower temperatures than LC
LW carcasses in both the loin and round. Select LW carcasses had numerically smaller ribeye areas compared to LC LW carcasses, suggesting Select LW carcasses were lighter muscled. Lighter muscling coupled with less marbling may explain how LL and ST muscles from Select LW carcasses were able to have lower carcass temperatures than muscles from LC LW carcasses No differences were observed in the loin and round of
Select and LC MW and HW carcasses throughout chilling. Additional heat production from postmortem metabolism in Select carcasses may be comparable to the heat retention of the higher grading LC carcasses explaining why Select and LC carcasses did not have temperature differences during the chilling period. These data demonstrate the complex relationship between temperature and quality grade.
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There are several methods the industry could employ to mitigate the effects of prolonged temperature declines of heavier carcasses, such as extended chilling time, arteriole chilling solution injection (Wang et al., 1995), and very rapid chilling at -4 to -
40C with air speed of 3–4.8 m/s for 1 to 3 h (Aalhus et al., 2001; Van Moeseke et al.,
2001; Aalhus et al., 2002; Li et al., 2012). Although, these methods could increase production efficiency, they result in variable product quality. Until further research is completed to determine optimal chilling conditions using these methods, they will be unlikely options for use in the beef industry.
Ultimate pH and Color
Regardless of HCW or QG, pHu of all muscles were within the expected ranges and are similar to previous studies (Tarrant and Sherington, 1980; Page et al., 2001; Hunt et al., 2014). No differences were observed in pHu for any muscle based on carcass weight (P > 0.54; Table 3.2). A decrease in pHu was observed when comparing Select SV steaks and LC SV steaks (P = 0.01; Table 3.2), but no differences were observed in pHu between Select and LC carcasses in the LL or ST. Page et al. (2001) reported a numerical decrease in pHu in the longissimus dorsi as QG increased. The decrease in pHu observed by Page et al. (2001) may be due to the differences observed for fat thickness: as fat thickness increased, pHu decreased. Since subcutaneous fat has insulation properties, the rate of pH decline would have occurred at a faster rate. At high temperatures, glycolysis can still occur and may not arrest until pH is below the normal values observed (5.4–5.6;
England et al., 2014). In the current study, accounting for backfat in the model for pHu may lead to similar observations as Page et al. (2001).
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In this study, SV and ST steaks from HW carcasses had increased L values compared to steaks from LW carcasses (P < 0.01; Table 3.2). Steaks from MW carcasses were generally similar in color to steaks from HW carcasses. An example of the differences observed for color between weight groups is provided in Figure 3.6. High pre-rigor temperature has been reported to result in pale beef color in the sternomandibularis, longissimus thoracis, and longissimus lumborum (Young et al.,
1999; Warner et al., 2014; Agbeniga and Webb, 2018; Hughes et al., 2018). Hughes et al.
(2018) suggested elevated temperatures increase the light scattering properties causing beef muscles to appear lighter. The increased lightness from steaks in HW carcasses may favor consumer satisfaction (Acebrón and Dopico, 2000).
Steaks from HW carcasses had increased a and b values compared to steaks from
LW carcasses in all three muscles (P < 0.01; Table 3.2). In the LL, a and b values were higher for steaks from MW carcasses compared to steaks from LW carcasses. Djimsa et al. (2019) reported no differences in a* in one plant but higher a* values in another plant for heavy weight carcasses (heavier than the plant average) compared to light weight carcasses (lighter than the plant average) in beef LL and psoas major muscles. The authors also reported higher b* values in steaks from heavy weight carcasses for both plants in both muscles. At 1 d of retail display, Lancaster et al. (2020) reported an increase in a* and b* in semimembranosus muscles from overweight (>432 kg) carcasses compared to average weight (341-397 kg) carcasses. No differences were reported by
Fevold et al. (2019) for a* between heavy (>408 kg) and light (<363 kg) carcasses in beef longissimus dorsi and semimembranosus; however, an increase in b* was observed in the steaks from heavy carcasses.
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No color differences were observed between Select and LC steaks in the LL and
ST (Table 3.2). Select SV steaks had decreased a (25.59 0.17) and b (10.29 0.16) values compared to LC SV steaks (a = 26.13 0.17, P = 0.03; b = 10.97 0.16, P <
0.01), which is similar to findings by Page et al. (2001) in the longissimus dorsi, in which the authors reported increasing a and b values with increasing QG. The values for a and b from Select carcasses were higher than those reported by Stetzer et al. (2008). This may be due to the heavier weights used in the current study, even in the LW group, compared to the Stetzer et al. (2008) study (270–320 kg). As previously discussed, HCW impacts rate of chilling, which in turn can impact color attributes.
Ultimate pH and color are related: a higher pHu results in a dark-appearing muscle and lower pHu results in a light-appearing muscle (Abril et al., 2001). Throughout chilling, no differences were observed for internal temperature between Select and LC carcasses in the chuck, so internal temperature is likely not the primary factor influencing the color differences observed in the chuck. Changes to muscle proteins, caused by changes in rate of pH decline, protein denaturation, and muscle structure, during the rigor process can also influence color (Hughes et al., 2018). In addition to structural changes, differences observed between Select and LC SV steaks could be a result of muscle fiber composition. Type I muscle fibers are more red in color, while Type II are more white
(Calkins et al., 1981). An increase in the percent Type I muscle fibers would likely result in steaks with higher a values.
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Sarcomere Length
In the current study, a QG HCW interaction was observed for sarcomere length in the LL (P = 0.03; Table 3.3). Sarcomeres in the LL were shorter in LC LW carcasses
(1.83 0.07 m) compared to LC MW (2.09 0.07; P = 0.02) and Select LW carcasses
(2.06 0.07 m; P = 0.03). Sarcomere length has been reported to be influenced by postmortem temperature extremes during chilling, as observed in cold-shortening and rigor (heat-induced) shortening (Locker and Hagyard, 1963). Loin temperatures of LC
LW carcasses exhibited temperatures between Select LW and LC MW loins yet LC LW loins had shorter sarcomere lengths compared to both Select LW and LC MW loins.
From these data, it can be concluded temperature decline was not the primary factor influencing sarcomere length. Other factors impacting sarcomere length are pHu and rate of pH decline (Smulders et al., 1990; Li et al., 2012). Ultimate pH was not different amongst HCW or QG in the LL and can be eliminated as the contributing factor to the variation in sarcomere lengths in the LL. Carcasses that have higher temperatures for extended periods can have a quicker pH decline (Li et al., 2012) which can shorten sarcomeres (Smulders et al., 1990). The relationship between HCW and sarcomere length requires additional research to determine how the rate of pH decline impacts sarcomere length in carcasses with higher temperatures.
Hot carcass weight influenced sarcomere length in the ST (P < 0.01; Table 3.4).
Sarcomere length in HW carcasses (1.82 0.05 m) was shorter than LW (2.08 0.05
m; P < 0.01) and MW carcasses (2.07 0.05 m; P < 0.01). Sarcomere lengths of LW and MW ST steaks were similar (P > 0.05). An image depicting the differences observed in sarcomere length in the ST between LW and HW carcasses is given in Figure 3.7.
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Rigor, or heat induced, shortening was observed by Locker and Hagyard (1963) and
Hertzman et al. (1993) in sternomandibularis, biceps femoris, semimembranosus, and semitendinosus muscles held at 25°C and 37°C during early postmortem chilling. Similar findings were reported by Hwang et al. (2004) in the longissimus lumborum and semitendinosus. Rigor shortening could have occurred in rounds in HW due to increased mass and the inability to dissipate heat at the same rate as rounds from lighter carcasses.
Contrary to these finding, Yu et al. (2008) reported increased sarcomere length in longissimus lumborum muscles held at 12°C for 4 h. Mohrhauser et al. (2014) and Kim et al. (2012) reported no differences in sarcomere length between coventional and delay chilled muscles. No differences were observed between HCW or QG in the SV (P >
0.05)which may be due to the muscles attachment to both the scapula and ribs.
Conclusion
This study shows beef HCW influence internal carcass temperatures during postmortem chilling, color, and sarcomere length. Elevated temperatures; increased lightness, redness, and yellowness of SV, LL, and ST steaks; and decreased sarcomere length in the ST were a result of HW carcasses. Differences observed for pHu and a and b values in Select SV and LC SV and sarcomere length in the LL warrant further investigation to understand the relationship HCW and QG have on these carcass traits in beef muscles. The beef industry faces challenges related to the chilling of heavier beef carcasses. Optimization of cooler loading (weight on the rail), carcass spacing, and utilization of different chilling systems will be important factors for the beef industry to
72 consider to continue producing high-quality beef for consumers despite a range of incoming HCW into the cooler.
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Morley, M. J. 1974. Measurement of the heat production in beef muscle during rigor mortis. Int. J. Food Sci. Tech. 9(2):149-156. doi: 10.1111/j.1365- 2621.1974.tb01758.x National Cattlemen’s Beef Association (NCBA). 2016. Beef quality audit. https://www.bqa.org/Media/BQA/Docs/2016nbqa_es.pdf (Accessed July 12 2019). Page, J. K., D. M. Wulf, and T. R. Schwotzer. 2001. A survey of beef muscle color and pH. J. Anim. Sci. 79(3):678-687. doi: 10.2527/2001.793678x Pentzer, W. T. 1966. The giant job of refrigeration. p 123-138. Rueden, C. T., J. Schindelin, M. C. Hiner, B. E. DeZonia, A. E. Walter, E. T. Arena, and K. W. Eliceiri. 2017. ImageJ2: ImageJ for the next generation of scientific image data. BMC Bioinformat. 18:529. doi: 10.1186/s12859-017-1934-z Sammel, L. M., M. C. Hunt, D. H. Kropf, K. A. Hachmeister, C. L. Kastner, and D. E. Johnson. 2002. Influence of chemical characteristics of beef inside and outside semimembranosus on color traits. J. Food Sci. 67(4):1323-1330. doi: 10.1111/j.1365-2621.2002.tb10282.x Schindelin, J., I. Arganda-Carreras, E. Frise, V. Kaynig, M. Longair, T. Pietzsch, S. Preibisch, C. Rueden, S. Saalfeld, B. Schmid, J.-Y. Tinevez, D. J. White, V. Hartenstein, K. Eliceiri, P. Tomancak, and A. Cardona. 2012. Fiji: An open- source platform for biological-image analysis. Nat. Methods 9:676-682. doi: 10.1038/nmeth.2019 Smulders, F. J., B. B. Marsh, D. R. Swartz, R. L. Russell, and M. E. Hoenecke. 1990. Beef tenderness and sarcomere length. Meat Sci. 28(4):349-363. doi: 10.1016/0309-1740(90)90048-B Stetzer, A. J., T. E., F. K. McKeith, and M. S. Brewer. 2008. Quality changes in beef complexus, serratus ventralis, vastus lateralis, vastus medialis, and longissimus dorsi muscles enhanced prior to aging. J. Food Sci. 73(1):S6-S10. doi: 10.1111/j.1750-3841.2007.00582.x Tarrant, P. V., and J. Sherington. 1980. An investigation of ultimate pH in the muscles of commercial beef carcasses. Meat Sci. 4(4):287-297. doi: 10.1016/0309- 1740(80)90028-5 United States Department of Agriculture, Agricultural Marketing Service (USDA-AMS). 2019. QAD Procedure 500: Beef, bullock, and bull grading methods and procedures. Agricultural Marketing Service, Washington, DC. United States Department of Agriculture, Agricultural Marketing Service (USDA-AMS). 2020. USDA national steer & heifer estimated grading percent report. https://mymarketnews.ams.usda.gov/filerepo/sites/default/files/2816/2020-12- 07/359169/ams_2816_00042.txt (Accessed 19 December 2020). United States Department of Agriculture, Economic Research Service (USDA-ERS). 2020. Livestock and poultry live and dressed weights. https://www.ers.usda.gov/ data-products/livestock-meat-domestic-data/livestock-meat-domesticdata/ #Livestock%20and%20poultry%20live%20and%20dressed%20weights (Accessed February 4 2020). Van Moeseke, W., S. De Smet, E. Claeys, and D. Demeyer. 2001. Very fast chilling of beef: effects on meat quality. Meat Sci. 59(1):31-37. doi: 10.1016/s0309- 1740(01)00049-3
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Wang, Y., M. D. S., R. R. Segado, and S. D. M. Jones. 1995. Vascular infusion of beef carcasses: Effects on chilling efficiency and weight change. Food Res. Int. 28(4):425-430. doi: 10.1016/0963-9969(95)00030-P Warner, R. D., F. R. Dunshea, D. Gutzke, J. Lau, and G. Kearney. 2014. Factors influencing the incidence of high rigor temperature in beef carcasses in Australia. Anim. Prod. Sci. 54(4):363-374. doi: 10.1071/an13455 Weaver, A. D., B. C. Bowker, and D. E. Gerrard. 2008. Sarcomere length influences postmortem proteolysis of excised bovine semitendinosus muscle. J. Anim. Sci. 86(8):1925-1932. doi: 10.2527/jas.2007-0780 Young, O. A., A. Priolo, N. J. Simmons, and J. West. 1999. Effects of rigor attainment temperature on meat blooming and colour on display. Meat Sci. 52(1):47-56. doi: 10.1016/s0309-1740(98)00147-8 Yu, L. H., D. G. Lim, S. G. Jeong, T. S. In, J. H. Kim, C. N. Ahn, C. J. Kim, and B. Y. Park. 2008. Effects of temperature conditioning on postmortem changes in physico-chemical properties in Korean native cattle (Hanwoo). Meat Sci. 79(1):64-70. doi: 10.1016/j.meatsci.2007.07.033
Table 3.1 Means (± SE) of carcass traits from USDA Select and low Choice carcasses selected to monitor internal temperature decline
LW1 MW1 HW1 P-value Average QG Se2 LC2 Se2 LC2 Se2 LC2 SE QG HCW HCW n 20 20 20 20 16 20 HCW, kg 323.6c 329.3c 407.7b 410.5b 479.9a 486.9a 2.7 0.02 <0.0001 0.72 REA4, cm2 80.3c 85.5c 95.8b 91.9b 107.3a 103.9a 2.0 0.65 <0.0001 0.03 Marbling3 354d 458a 363cd 442b 374c 446ab 5.5 <0.0001 0.42 0.01 Backfat4, cm 1.0c 1.0c 1.2bc 1.3bc 1.4b 1.7a 0.1 0.12 <0.0001 0.26
Yield grade 2.61bc 2.4c 2.7bc 3.0b 2.9b 3.5a 0.1 0.11 0.0002 0.06 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice 3Marbling scores are as follows: 300–399 = Slight, 400–499 = Small 4Measured between the 12th and 13th ribs a-d Means with different superscripts within a row differ (P < 0.05)
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Table 3.2 Mean (± SE) for ultimate pH (pHu) and color (Hunter L, a, b) of the serratus ventralis (SV), longissimus lumborum (LL), and semitendinosus (ST) from USDA Select and low Choice beef carcasses
Weight1 Quality Grade2 Average Average LW MW HW SE P-value Se LC SE P-value pHu SV 5.79 5.79 5.80 0.02 0.96 5.77 5.82 0.02 0.01 LL 5.58 5.59 5.58 0.01 0.87 5.59 5.58 0.01 0.58 ST 5.55 5.54 5.56 0.02 0.54 5.55 5.54 0.02 0.64
L3,4 SV 41.08b 41.98ab 43.05a 0.41 0.0048 41.82 42.25 0.33 0.36 LL 38.68 39.37 39.84 0.37 0.09 38.94 39.66 0.30 0.09 ST 43.25b 44.81a 45.16a 0.35 0.0006 44.26 44.55 0.29 0.48 a3,4 SV 25.00c 25.88b 26.71a 0.21 <0.0001 25.59 26.14 0.17 0.03 LL 23.18b 23.97a 24.29a 0.18 0.0002 23.83 23.80 0.15 0.86 ST 24.70b 25.68a 26.18a 0.24 0.0002 25.33 25.71 0.19 0.18 b3,4 SV 9.88b 10.75a 11.25a 0.35 <0.0001 10.29 10.97 0.15 0.0027 LL 8.68b 9.33a 9.70a 0.16 0.0001 9.16 9.32 0.13 0.42
ST 10.52b 11.74a 12.28a 0.23 <0.0001 11.28 11.75 0.18 0.07 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice 3Color was determined after a 15 min bloom period 4L: 0 = black, 100 = white; a: negative = green, positive = red; b: negative = blue, positive = yellow abc Means with different superscripts within a row for weight differ (P < 0.05)
Table 3.3 Mean (± SE) for sarcomere lengths (µm) of steaks from the longissimus lumborum from USDA Select and low Choice beef carcasses as measured at 5 d postmortem LW1 MW1 HW1 P-value Average QG Se2 LC2 Se2 LC2 Se2 LC2 SE QG HCW HCW LL 2.06a 1.83b 1.94ab 2.09a 2.00ab 2.03ab 0.07 0.79 0.59 0.03 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice ab Means with different superscripts differ (P < 0.05)
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Table 3.4 Mean (± SE) for sarcomere lengths (µm) of steaks from the serratus ventralis and semitendinosus muscles from USDA Select and low Choice beef carcasses as measured at d5 postmortem
Weight1 Quality Grade2 Average Average LW MW HW SE P-value Se LC SE P-value SV3 2.12 2.07 2.13 0.03 0.69 2.11 2.10 0.02 0.50
ST3 2.08a 2.07a 1.82b 0.05 0.0014 1.96 2.01 0.04 0.44 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Se = USDA Select; LC = low Choice 3SV = serratus ventralis; ST = semitendinosus ab Means with different superscripts within a row are significantly different (P < 0.05)
81
Figure 3.1 Data logger location in the a) round, b) chuck, and c) loin
A)
B)
C)
82
Figure 3.2 Steak fabrication guide for a) serratus ventralis, b) longissimus dorsi, and c) semitendinosus
A
B
C
Figure 3.3 Internal temperature decline in loin primals of USDA Select (Se) and low Choice (LC) beef carcasses from three weight groups1 (n = 115) selected prior to entering the cooler
42 P = 0.03 Se LW LC LW Se MW LC MW 36 Se HW LC HW
30
C)
( 2 24
18
Temperature 12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Temperature data loggers (10.16 cm in length) were placed in the geometric center of the longissimus lumborum 50 min postmortem and temperature reported every 15 min
83
Figure 3.4 Internal temperature decline in round primals of USDA Select (Se) and low Choice (LC) beef carcasses from three weight categories1 (n = 110) selected prior to entering the cooler
42 P < 0.0001 Se LW LC LW Se MW LC MW 36 Se HW LC HW
30
C)
( 2 24
18
Temperature 12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Temperature data loggers (20.32 cm in length) were placed in the center of the round near, but not touching, the femur 48 min postmortem and temperature reported every 15 min
84
Figure 3.5 Internal temperature decline in chuck primals by a) hot carcass weight1 and b) quality grade of USDA Select (Se) and low Choice (LC) beef carcasses (n = 116) selected prior to entering the cooler
A 42 P < 0.0001 LW MW HW
36
30
C)
( 2 24
18
Temperature 12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
85
B 42 P = 0.87 Se LC
36
30
C)
( 2 24
18
Temperature 12
6
0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Time (h)
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Temperature data loggers (20.32 cm in length) were placed posterior to the scapula at the junction between the brisket and foreleg in the serratus ventralis 50 min postmortem and temperature reported every 15 min
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87
Figure 3.6 Representative color images of light weight and heavy weight semitendinosus steaks
HEAVY
LIGHT
88
Figure 3.7 Representative sarcomere length images of a) light weight and b) heavy weight semitendinosus muscles A)
B)
89
Chapter 4
Beef hot carcass weight impacts tenderness and protein degradation of steaks from USDA Select and low Choice carcasses
90
Abstract
Postmortem proteolysis and tenderization of beef muscles can be influenced by internal carcass temperature during chilling. The objective of this study was to investigate the impact of hot carcass weight (HCW) on Warner-Bratzler shear force (WBSF), cook loss, and proteolysis of troponin-T and desmin in the serratus ventralis (SV),
Longissimus lumborum (LL), and semitendinosus (ST) muscles of USDA Select and low
Choice (LC) beef carcasses. Carcasses were selected by HCW (light = 296–341 kg; middle = 386–432 kg; heavy = 466–523 kg) at a commercial beef packing facility.
Following chilling, subprimals were obtained from a sub-sample of USDA Select and LC carcasses for analyses. A HCW aging day interaction was observed for WBSF in LL steaks (P < 0.01). At 5 d, LL steaks from light weight carcasses were tougher than all other weight groups and aging days. In the SV and ST, steaks aged 5 d were tougher than steaks aged 10 d and 14 d (P < 0.0001). An increased abundance of the 30 kDa troponin-
T degradation products was observed in SV steaks from LC heavy weight carcasses compared to all other weight groups and quality grades (P < 0.01). Abundance of the 30 kDa troponin-T degradation product increased with aging day in the LL and ST (P <
0.01). In the SV, the abundance of the 35 kDa desmin degradation product was increased in light and middle weight carcasses (P < 0.0001) and at 10 d and 14 d of aging (P <
0.0001). A quality grade HCW aging day interaction was observed for the 35 kDa desmin degradation product in the LL (P = 0.03), but all steaks had a similar abundance of the 35 kDa desmin degradation product by 14 d of aging. In the ST, a quality grade
HCW interaction was observed for the 35 kDa desmin degradation product (P = 0.02).
Heavier carcasses had earlier tenderization and decreased extent of tenderization
91 suggesting the internal carcass conditions during postmortem chilling impact proteolytic enzyme activity during postmortem aging.
Introduction
Producing a product with a consistent eating experience in an industry with large variations in carcass size and composition is a challenge for the beef industry. Carcass weight has increased 70 kg the past 30 years (USDA-ERS, 2020). In the previous chapters, it was reported heavier carcasses (>465 kg) had higher internal temperatures for an extended period of time during chilling compared to lighter carcasses. Additionally, higher internal carcass temperatures were observed in larger primals, such as the round.
Higher internal carcass temperatures during postmortem chilling can negatively impact enzymatic systems involved in postmortem aging as reported by Koohmaraie (1992), Bee et al. (2007), and Kim et al. (2012) in in vitro systems and excised muscles. Reduced enzymatic activity may result in beef products with inferior quality. Research on the influence of higher temperature of non-excised muscles in heavy weight carcasses on tenderness and postmortem aging is limited. In addition to hot carcass weight (HCW), the effects of quality grade on temperature decline were variable, as reported in Chapter 3.
The hypothesis of this study was increased HCW will result in decreased tenderization and increased toughness in steaks. The objective of this study was to investigate the influence of beef HCW on Warner-Bratzler shear force (WBSF), cook loss, and proteolysis of troponin-T and desmin in the serratus ventralis, Longissimus lumborum, and semitendinosus muscles of USDA Select and low Choice beef carcasses.
92
Materials and Methods
Carcass Selection and Sample Processing
Carcasses were selected and samples collected as described in Chapter 3. Briefly,
A-maturity carcasses were selected at a commercial beef packing facility based upon
HCW [light (LW) = 296–341 kg; middle (MW) = 386–432 kg; heavy (HW) = 466–523 kg]. A subsample of carcasses was selected from the USDA Select and low Choice (LC) carcasses monitored for temperature decline. Subprimals from the subsample of carcasses were transported to the South Dakota State University Meat Laboratory, trimmed of excess fat, and fabricated into steaks. A 2.54 cm thick steak was used for WBSF and 0.64 cm thick steak for proteolytic analysis. The serratus ventralis (SV; Figure 4.1a) was dissected along the major seam. All steaks were removed from the posterior portion of the SV (steaks 1-3 for WBSF, steaks 4-6 for proteolysis). The anterior face of the longissimus lumborum (LL; Figure 4.1b) and additional three inches was removed prior to steak fabrication. Steaks were collected from the medial portion of the LL (steaks 1-3 for WBSF, steaks 4-6 for proteolysis). The semitendinosus (ST; Figure 4.1c) was bisected along the medial plane prior to fabricating into steaks. Starting from the anterior end, the first three steaks (steaks 1-3) were used for proteolysis. From the point of the bisection, the first three steaks from the posterior half of the ST (steaks 4-6) were used for WBSF.
Samples were vacuum packaged (3 mm; Koch Supplies, Riverside, MO) and aged 5, 10, or 14 d at 2–4C. Samples were frozen (-20C) until analyzed.
93
Warner Bratzler Shear Force and Cook Loss
Warner-Bratzler shear force followed the procedures outlined by the American
Meat Science Association (AMSA, 2015). Steaks were removed from the freezer and allowed to equilibrate to 4C prior to cooking. Steaks were cooked to an internal temperature of 71C using a clamshell grill (George Foreman model GR2144P;
Beachwood, OH). Internal temperature was monitored using thermocouples (model
39658-K; Atkins Technical, Gainesville, FL). Steaks were weighed before and after cooking to determine cook loss. Following a 24 h chilling period at 4C, steaks were equilibrated to room temperature. Six cores (1.27 cm diameter) were taken parallel to the muscle fibers and sheared at a crosshead speed of 20 cm/min using a texture analyzer
(Shimadzu, model EZ SX; Suzhou Instruments Manufacturing, Co., LTD, Jiangsu,
China) and TrapeziumX software (v 1.5.1; Suzhou Instruments Manufacturing, Co.,
LTD). The average of the cores was used for statistical analysis.
Protein Extraction and Gel Sample Preparation
Frozen samples were thawed approximately one hour, sliced into 1-2 mm pieces, and frozen in liquid nitrogen for one minute. Nitrogen-frozen samples were powdered in stainless steel blender cups using a commercial blender (model 51BL32; Waring,
Torrington, CT) for 5–7 s bursts until the sample was uniformly powdered. Powdered samples were stored at -10C until further analysis.
Gel samples were prepared using the methods outlined by Melody et al. (2004) with modifications. Briefly, 0.65 g of powdered sample was placed in 10 ml whole muscle buffer [2% sodium dodecyl sulfate (SDS), 10 mM sodium phosphate]. Samples
94 were homogenized on high speed for 2 minutes using an over-head stirrer (model RZR1;
Heidolph, Schwabach, Germany). Homogenized samples were centrifuged for 20 min at
3000 RPM (1700 x g) at 25C. Protein concentration was determined using the DC
Lowry protein assay (BioRad, Hercules, CA). Gel samples, 3.76 mg/ml, were placed in a heating block at 60C for 15 min to denature proteins. Samples were frozen immediately and stored at -10C.
Load check gels were run to ensure proper dilution during protein extraction and gel sample preparation. Samples were run on 15% SDS polyacrylamide separating gels
[acrylamide:N,N’-bis-methylene acrylamide = 100:1, 0.1% SDS, 0.05% tetramethyethylenediamine (TEMED), 0.05% ammonium persulfate (APS), and 0.375 M
Tris-HCl (pH 8.8)] with 5% stacking gels (acrylamide:N,N′-bis-methylene acrylamide =
100:1, 0.1% SDS, 0.125% TEMED, 0.075% APS, and 0.125 M TrisHCl (pH 6.8)]. Gels were run using a mini gel electrophoresis unit (model SE-260; Hoefer Scientific
Instruments) at 120 V for approximately 3 hours. Gels were stained using a blue staining dye (40% methanol, 7% glacial acetic acid, 0.1% Coomassie brilliant blue R-250) for 24 h, washed using 40% methanol and 7% glacial acetic acid, and visually analyzed using a
FluorChem M multi-fluor imaging system (Protein Simple, Santa Clara, CA).
Western Blot Analysis
Troponin-T and desmin were analyzed on 15% and 10% polyacrylamide separating gels, respectively, with 5% polyacrylamide stacking gels. Gels were run on the mini gel electrophoresis units previously described for an average of 390 volt-hours for troponin-T and 300 volt-hours for desmin. Running buffer contained 50 mM Tris, 384
95 mM glycine, 0.2% SDS, and 0.4 mM ethylenediaminetetraacetic acid (EDTA). Gels were transferred to a 0.45 m polyvinylidene difluoride membrane (Immobilon, Darmstadt,
Germany) for 90 min at 90 V. Temperature of the transfer buffer (24 mM Tris, 186 mM glycine, 15% methanol) was maintained at 4C using a refrigerated water bath (IsoTemp, model 6200 R28; Thermo Fisher Scientific, Asheville, NC). Membranes were blocked using a 0.5% non-fat dry milk solution for 1 h at room temperature. Troponin-T blots were incubated overnight at 4C with JLT-12 primary antibody (Sigma, St. Louis, MO) diluted in phosphate buffer solution (PBS; 66 mM sodium phosphate, 0.1 M NaCl) to
1:15,000; desmin blots were incubated overnight at 4C with rabbit anti-desmin primary antibody (obtained from the Lonergan lab, Iowa State University) diluted in PBS to
1:80,000. Blots were warmed to room temperature and washed for 10 min in PBS with tween (PBST; PBS + 0.1% Tween-20) three times. Secondary antibody was applied to each membrane [troponin-T: goat anti-mouse horseradish peroxidase (Thermo Fisher
Scientific) diluted in PBS to 1:20,000; desmin: goat anti-rabbit horseradish peroxidase
(Thermo Fisher Scientific) diluted in PBS to 1:20,000] for 1 h at room temperature. Blots were washed for 10 min three times using PBST following secondary antibody incubation. A final wash was completed using PBS. Membranes were developed using the ECL Prime detection kit from GE Healthcare (Lafayette, CO). Images were obtained via chemiluminescence using the imaging system previously described and blots analyzed using the AlphaView program (v 3.4.0.0; Protein Simple). Appearance of the 30 kDa troponin-T and 35 kDa desmin degradation products were analyzed. Samples were reported as a ratio of the sample to an internal standard analyzed on the same gel. The
96 average between two blots (coefficient of variation <20%) was used for statistical analysis.
Statistical Analysis
Warner Bratzler shear force, cook loss, and protein data were analyzed as repeated measures using the unstructured covariance structure in the MIXED procedure in SAS (v 9.4; SAS Inc., Cary, NC) for the effects of HCW, quality grade (QG), aging day, and their interactions. Peak temperature during cooking was included as a covariate for WBSF and cook loss. Separation of least square means were determined using a post- hoc Tukey-Kramer analysis at = 0.05.
Results and Discussion
Warner Bratzler Shear Force
In the SV, an aging day effect was observed for WBSF. Steaks aged 5 d had the highest WBSF, 10 d were an intermediate and 14 d had the lowest WBSF (P < 0.0001;
Figure 4.2a). No HCW or QG effect was observed for WBSF in the SV (P = 0.36 and P =
0.58, respectively; Table 4.1). In the LL, QG was not significant for WBSF (P = 0.62;
Table 4.1). A HCW aging day interaction was observed for WBSF in the LL (P < 0.01;
Figure 4.2b); Steaks from the LL aged 5 d were the least tender in LW steaks compared to all other weight groups and aging days (P < 0.01). Light weight LL steaks aged 10 d had increased toughness compared to 10 d MW and 10 d HW steaks (P = 0.03). At 14 d of aging, all LL steaks had achieved similar WBSF values. Longissimus lumborum steaks from LW carcasses had improved tenderness from 10 d to 14 d of aging (P = 0.02),
97 whereas LL steaks from MW and HW carcasses did not have improved tenderness between 10 d and 14 d of aging. In the ST, an aging day effect was observed. Warner
Bratzler shear force was highest for 5 d steaks, intermediate for 14 d steaks, and lowest for 10 d steaks (P < 0.0001; Figure 4.2c). Hot carcass weight and QG did not impact
WBSF in the ST (P = 0.66 and P = 0.81, respectively; Table 4.1). Phelps et al. (2016) reported a location effect on WBSF values of ST steaks. At either end of the muscle,
WBSF increased. Towards the middle of the muscle, approximately where samples were obtained for the current study, Phelps et al. (2016) reported a decrease in WBSF. A measure of sarcomere length of the same steaks used for WBSF may also explain the differences observed as sarcomere length influences tenderness (Locker and Hagyard,
1963) and postmortem aging (Weaver et al., 2008).
Increased internal temperatures early postmortem can negatively influence the aging process and tenderization by negatively impacting proteolytic enzyme activity
(Koohmaraie, 1992). Heavier beef carcasses had higher temperatures during early postmortem chilling in the SV, LL, and ST as reported in Chapter 3. In the current study,
WBSF of the LL was the only muscle influenced by HCW. At early aging times, steaks from LW carcasses were less tender than steaks from MW and HW carcasses, which may be a result of the lower internal temperatures during early postmortem chilling potentially contributing to the shorter sarcomere lengths that were observed in Chapter 3 between steaks from LW and MW carcasses. Hwang et al. (2004) reported the extent of proteolysis during aging may be able to overcome the impact of decreased sarcomere length, explaining why LL steaks from LW carcasses were able to be of similar tenderness to MW and HW by 14 d of aging. Improved tenderness in steaks from muscles
98 with higher temperatures is supported by Thomson et al. (2008) who reported decreased
WBSF at 1 d of aging in steaks from longissimus dorsi muscles held at 36C compared to
LL muscles held at 15C until a pH 5.6. Contrary to these findings, Kim et al. (2012) reported increased WBSF values in the LL when the pre-rigor temperature was 38C compared to 15C. The different portions of the longissimus used in the studies may be one reason for the differences observed between the Thomson et al. (2008) and Kim et al.
(2012) studies. Kim et al. (2012) suggested the difference in pre-rigor temperature (36C v. 38C) may be enough to increase protein denaturation resulting in less tender steaks.
Additional studies have reported a limited extent of tenderization during postmortem aging due to earlier inactivation of proteolytic enzymes. Thomson et al.
(2008) reported proteolysis of LD muscles held at 36C during the postmortem aging period was not to the same extent as LD muscles held at 15C. In the current study, steaks from LW carcasses had a 23.6% improvement in tenderness from 5 d to 10 d, whereas MW and HW had 16.6% and 13.1%, respectively. At 14 d, steaks from MW and
HW carcasses had no improvement to tenderness, while steaks from LW carcasses continued to increase in tenderness, indicating steaks from LW carcasses continue to age past 14 d.
A WBSF value of 4.6 kg has often been reported as the average at which consumers begin to consider steaks as “tender” or “tough” (Shackelford et al., 1991;
Miller et al., 2001; Hunt et al., 2014). Regardless of treatment, SV steaks from the current study were below this threshold to be considered “tender” after aging for 5 d. Steaks from the LL in MW and HW carcasses would be considered “tender” after 10 d of aging, and
LL steaks from LW carcasses would be considered tender after 14 d of aging. Miller et al.
99
(2001) suggested tenderness could be influenced by variations in juiciness and flavor of steaks, so it is important to consider other sensory attributes when assessing tenderness.
No steaks from the ST were below 4.6 kg. In the current study, ST steaks were 6.0 kg at
14 d of aging, similar to Phelps et al. (2016), who reported ST steaks were 5.1 kg at 14 d of aging. The ST has increased amounts of collagen, is a slower aging muscle, and would be expected to have increased WBSF values in comparison to many other beef muscles
(Rhee et al., 2004; Calkins and Sullivan, 2007; Phelps et al., 2016).
Cook Loss
In the SV, a QG HCW aging day interaction (P = 0.01) was observed for cook loss (Figure 4.3a). Cook loss was decreased in 10 d LC steaks from MW carcasses (23.2
± 0.7%) compared to 5 d Select LW (25.3 ± 0.7%; P = 0.02), 5 d LC MW (25.3 ± 0.7%;
P < 0.01), 5 d Select MW (25.0 ± 0.7%; P = 0.04), 5 d Select HW (25.9 ± 0.8%; P <
0.01), 5 d LC HW (25.8 ± 0.7%; P < 0.01), 10 d LC LW (25.0 ± 0.7%; P = 0.04), and 14 d Select LW (25.4 ± 0.9%; P = 0.03). Cook loss was decreased in 10 d Select steaks from
LW carcasses (23.4 ± 0.7%) compared to 5 d Select LW (25.3 ± 0.7%; P = 0.02) and 5 d
Select HW. A decrease in cook loss was observed in 10 d LC steaks from MW carcasses
(23.2 ± 0.7%) compared to 5 d Select LW (25.3 ± 0.7%; P = 0.02), 5 d LC MW (25.3 ±
0.7%; P < 0.01), 5 d Select MW (25.0 ± 0.7%; P = 0.04), 5 d Select HW (25.9 ± 0.8%; P
< 0.01), 5 d LC HW (25.8 ± 0.7%; P < 0.01), 10 d LC LW (25.0 ± 0.7%; P = 0.04), and
14 d Select LW (25.4 ± 0.9%; P = 0.03).
In the LL an aging day effect was observed for cook loss (P < 0.01; Figure 4.3b).
Cook loss was highest for 5 d aged steaks (19.8 ± 0.2%), intermediate for the 14 d aged
100 steaks (19.4 ± 0.2%), and lowest for 10 d aged steaks (18.2 ± 0.2%). Hot carcass weight and QG did not influence cook loss in LL steaks (P = 0.10 and P = 0.63, respectively;
Table 4.2). Colle et al. (2015) reported no change in percent cook loss from LL steaks aged 2 d and 14 d, which supports the data of the current study. Li et al. (2012) and Kim et al. (2021) reported no difference in cook loss of LL steaks aged 1, 7, 14, and 21 d.
In the ST, a QG HCW interaction was observed for cook loss (P = 0.04; Figure
4.3c). Steaks from Select LW carcasses had decreased cook loss (28.7 ± 0.3%) compared to steaks from LC LW (29.7 ± 0.3%; P = 0.04), Select MW (30.2 ± 0.3%; P < 0.01),
Select HW (30.3 ± 0.4%; P < 0.01), and LC HW (29.8 ± 0.3%; P = 0.03) carcasses. An aging effect was also observed for cook loss in the ST (P < 0.0001; Figure 4.3d). Cook loss was increased for 5 d aged ST steaks compared to 10 d and 14 d aged steaks.
Water holding capacity (WHC) is a result of the extent of protein denaturation and can be measured using drip loss, purge, and cook loss. Slow chilling of carcasses increases water loss in meat products due to the increased protein denaturation occurring at the higher temperatures (den Hertog-Meischke et al., 1997). When protein denaturation is increased, myofibrils shrink, which reduces the space available for water and increases water loss either during the rigor process, storage, or cooking (den Hertog-Meischke et al., 1997; Melody et al., 2004). As reported by Melody et al. (2004) and Davis et al.
(2004) in pork muscles, the aging process, particularly the increased degradation of desmin, results in meat products with a higher WHC. It would be expected further aged products would have decreased cook loss due to the expected increased protein degradation.
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In the current study, cook loss generally decreased from 5 d to 10 d steaks; however, cook loss from 10 d to 14 d aged steak was variable with muscle. In beef semimembranosus muscles, Mungure et al. (2016) reported an increase in cook loss as aging day increased from 3 d to 7 d. The authors attributed this increase in cook loss to increased degradation of myofibrillar proteins resulting in decreased WHC and increased cook loss. Mungure et al. (2016) reported no further increases in cook loss between 7 d and 21 d of aging. Daszkiewicz et al. (2003) reported increased juice expression and decreased WHC of beef longissimus dorsi steaks aged 3 d and 7 d compared to steaks aged 10 d and 14 d, corresponding to the observed slight improvement in juiciness of sensory panels.
In addition to aging day, the SV and ST were influenced by HCW and QG. In general, as HCW increased, cook loss increased. Heavier carcasses used for the current study were reported to have higher temperatures during postmortem chilling (Chapter 3).
Hwang et al. (2004) also reported LL and ST muscles held at higher temperatures had an increase in cook loss. Offer and Trinick (1983) reported cook loss is increased in muscles that are pale, soft, and exudative-like, which round muscles may experience due to the high postmortem temperatures and rapid pH decline (Kim et al., 2010). Lancaster et al.
(2020) reported no differences in cook loss for semimembranosus muscles from average weight (341-397 kg) and overweight (>432 kg) beef carcasses. The difference between their study and the current study may be due to the difference in HCW collected. The average overweight carcass, reported by Lancaster et al. (2020) was 462 kg, with the heaviest carcasses weighing 500 kg. In the current study, the average HCW for the HW group was 484 kg, with the heaviest carcass weighing 525 kg. The difference in weight
102 could be enough to result in more extreme temperature differences, increased protein denaturation, and increased cook loss. Although the ST and semimembranosus muscles are from the same primal, the muscles do have slightly different characteristics
(Kirchofer et al., 2002; Rhee et al., 2004) and experience different temperature dynamics during chilling that could impact cook loss observed.
Purge loss was not accounted for in this study and total water loss not calculated.
To note, noticeable differences in the amount of purge were observed in the packaging during subprimal fabrication and cooking. Total water loss would be a better indicator of
WHC throughout the storage and cooking process and may help to explain some of the differences observed with cook loss.
Troponin-T Degradation
Proteolysis during postmortem aging can be assessed by measuring the density or abundance of intact or degraded proteins in a sample. The 30 kDa degradation product of troponin-T (TnT) is commonly analyzed because of its strong association with meat tenderness (MacBride and Parrish Jr., 1977; Olson and Parrish Jr., 1977). Figure 4.4 is a representative Western blot for TnT. A QG HCW interaction was observed for the 30 kDa TnT degradation product in the SV (P < 0.01; Figure 4.5). Steaks from LC HW carcasses had an increased abundance of the 30 kDa TnT degradation product compared to steaks from Select and LC LW, Select and LC MW, and Select HW carcasses (P <
0.0001). Aging day was not significant for the 30 kDa TnT degradation product in the SV
(P = 0.89; Table 4.3). An aging day effect was observed in both the LL (Figure 4.6) and
ST (Figure 4.7), with steaks aged 5 d having a lower abundance of the 30 kDa TnT
103 degradation product than 10 d and 14 d steaks (P < 0.0001). Neither HCW or QG influenced abundance of the 30 kDa TnT degradation product in the LL or ST (P > 0.05;
Table 4.3). The results of the appearance of the 30 kDa TnT degradation product in the
LL and ST support the results observed for WBSF.
The effects of increased temperatures to postmortem proteolysis are variable.
Koohmaraie (1992) reported a decreased abundance of the inactive form of proteolytic enzymes in an in vitro system at 25C compared to 5C. Hwang et al. (2004) reported increased rates of TnT degradation at higher temperatures in LL and ST muscles. In the current study, no differences were observed between weight groups in the LL and ST, despite HW carcasses having higher temperatures during chilling as reported in Chapter
3. However, LC HW carcasses had increased TnT degradation in the SV, indicating there may be earlier postmortem aging in LC HW carcasses. The abundance of degraded TnT continued to increase in the SV as aging progress.
Desmin Degradation
Desmin degradation was analyzed because of its association to overall protein degradation (Hwan and Bandman, 1989; Whipple and Koohmaraie, 1991). Figure 4.8 is a representative Western blot for desmin. In the SV, both a HCW (P < 0.0001; Figure 4.9a) and aging day effect were observed for desmin degradation (P < 0.0001; Figure 4.9b).
The abundance of the 35kDa desmin degradation product was increased in LW and MW carcasses (P < 0.0001) and at 10 d and 14 d of aging (P < 0.0001). The abundance of the
35 kDa desmin degradation product in the SV was not influenced by QG (P = 0.13; Table
4.4).
104
A QG HCW aging day interaction was observed for the 35 kDa desmin degradation product in the LL (P = 0.03; Figure 4.10). The abundance of the 35 kDa desmin degradation product was lower in 5 d Select LW steaks compared to 5 d Select
MW, 10 d Select LW, 10 d LC LW, 10 d Select MW, 10 d LC MW, 10 d Select HW, 14 d Select LW, 14 d LC LW, 14 d LC MW, 14 d Select HW, and 14 d LC HW (P < 0.05).
The abundance of the 35 kDa desmin degradation product was greater in LC MW steaks aged 10 d compared to 5 d LC LW, 5 d LC MW, 5 d Select HW, 5 d LC HW, 10 d LC
HW, 14 d Select LW, and 14 d Select MW (P < 0.05). By 14 d of aging, all LL steaks had the same abundance of the 35 kDa desmin degradation product across all treatments.
In the ST, a QG HCW interaction was observed for the appearance of the 35 kDa desmin degradation product (P = 0.02; Figure 4.11a). Degraded desmin was increased in LC LW and Select MW compared to Select LW carcasses (P < 0.05). An aging day effect was observed in ST steaks (P < 0.0001; Figure 4.11b) with 5 d steaks having the lowest abundance of the 35 kDa desmin degradation product, 10 d steaks an intermediate, and 14 d steaks having the greatest abundance of the 35 kDa desmin degradation product.
As observed with TnT, desmin degradation was influenced by HCW in all three muscles. Despite higher temperatures in heavier carcasses, proteolysis continued throughout the 14-d aging period. In beef semimembranosus muscles, Kim et al., (2010) reported decreased desmin degradation at 14 d in the deep portion of the semimembranosus where muscle temperature was higher during the chilling period compared to the superficial semimembranosus where muscle temperature was lower during chilling. This was not observed in the ST in the current study. No difference was
105 observed for the abundance of degraded desmin in ST muscles from LW and HW carcasses experiencing different internal carcass temperatures during chilling. However,
Select MW carcasses did have an increased abundance of the 35 kDa desmin degradation product in the ST compared Select LW carcasses. The effect of QG in the LL and ST indicates there is a relationship between QG and proteolysis which is yet to be understood.
Conclusion
Hot carcass weight influenced cook loss in the SV and ST and WBSF in the LL.
The rate and extent of tenderization was influenced by HCW. Tenderization appears to occur earlier during postmortem aging as HCW increases, suggesting proteolytic enzyme activity is impacted by postmortem conditions. However, aging up to 14 d helped to reduce the tenderization differences observed resulting in more uniform beef products for consumers. Beef packers processing larger cattle should feel confident USDA Select and
LC products being marketed will meet consumer expectations for tenderness provided a sufficient aging period.
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Table 4.1 Means (± SE) for Warner-Bratzler shear force (WBSF; kg) of steaks from USDA Select (Se) and low Choice (LC) carcasses Weight1 LW MW HW SE P-value Serratus ventralis 3.5 3.7 3.7 0.1 0.36 Semitendinosus 6.2 6.1 6.3 0.1 0.66
Grade Se LC Serratus ventralis 3.6 3.6 0.1 0.58 Longissimus lumborum 4.7 4.8 0.2 0.56 Semitendinosus 6.2 6.2 0.1 0.81 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg
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Table 4.2 Means (± SE) for percent cook loss of steaks from the longissimus lumborum from USDA Select and low Choice (LC) carcasses Cook loss SE P-value 1 Weight LW 19.62 0.23 0.10 MW 19.53 HW 18.95
Grade Select 19.43 0.19 0.63 LC 19.30 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg
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Table 4.3 Means (± SE) for the abundance1 of the 30 kDa troponin-T degradation product for steaks from USDA Select (Se) and low Choice (LC) carcasses Weight2 LW MW HW SE P-value Longissimus lumborum 1.47 1.57 1.56 0.08 0.63 Semitendinosus 0.78 0.87 0.86 0.08 0.69
Grade Se LC Longissimus lumborum 1.47 1.59 0.07 0.21 Semitendinosus 0.87 0.81 0.06 0.51
Age 5 10 14 Serratus ventralis 0.40 0.42 0.39 0.05 0.89 1Values are reported as a ratio of the sample protein to an internal standard sample 2LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg
112
Table 4.4 Means (± SE) for the abundance1 of the 35 kDa desmin degradation product for serratus ventralis steaks from USDA Select (Se) and low Choice (LC) carcasses Desmin SE P-value Se 0.91 0.07 0.13 LC 1.05 0.07 1Values are reported as a ratio of the sample protein to an internal standard sample 2LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg
113
Figure 4.1 Steak fabrication guide of the a) serratus ventralis, b) longissimus lumborum, and c) semitendinosus. Warner-Bratzler shear force (WBSF) steaks were cut to 2.54 cm and proteolysis steaks to 0.64 cm
A
B
C
114
Figure 4.2 Mean (± SE) Warner-Bratzler shear force (WBSF) of the a) serratus ventralis, b) longissimus lumborum, and c) semitendinosus from USDA Select and low Choice carcasses
A 5 a 4 b c 3 2
1 WBSF (kg) WBSF 0 5 10 14 Aging day
B 7 a 6 bc bc b cf ef 5 def f d ef 4 e 3
2 WBSF (kg) WBSF 1 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight1 and aging day
C 7 a c b 6 5 4 3 2
WBSF (kg) WBSF 1 0 5 10 14 Aging day
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-f Means with different superscripts differ (P < 0.05)
115
Figure 4.3 Means (± SE) for cook loss of the a) serratus ventralis, b) longissimus lumborum, c) interaction of quality grade × HCW in the semitendinosus, and d) aging day effect in the semitendinosus from USDA Select (Se) and low Choice (LC) carcasses
A 30 a ab ab ac abc ad ac ad a ad ad ad ad ad 25 cd ab bd d
20 Se 5 Se 10 15 Se 14
10 LC 5 Cook loss (%)loss Cook 5 LC 10 LC 14 0 LW MW HW Weight1
B 21 a c b 18 15 12 9
Cook loss (%)loss Cook 6 3 0 5 10 14 Aging day
116
C 35 a a ab a a 30 b 25 20 15
10 Cook loss (%)loss Cook 5 0 Se LC Se LC Se LC LW MW HW Weight1 and quality grade
D 35 a 30 b b 25 20 15
Cook loss (%)loss Cook 10 5 0 5 10 14 Aging day
1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-d Means with different superscripts differ (P < 0.05)
117
Figure 4.4 Representative Western blot for Troponin-T. Samples were run on 15% SDS- PAGE gels and transferred to PVDF membrane. Membranes were blocked with a 0.5% non-fat dry milk solution, then incubated overnight at 4°C in JLT-12 troponin-T antibody (1:15,000). Goat-anti mouse was used as the secondary antibody (1:20,000)
30 kDa
118
Figure 4.5 Means (± SE) for abundance of the 30 kDa troponin-T degradation product in the serratus ventralis from USDA Select (Se) and low Choice (LC) beef carcasses
0.8 a
1 0.7 T - 0.6 0.5 b b b b 0.4 b 0.3 0.2
Ratio of Ratio troponin 0.1 0 Se LC Se LC Se LC LW MW HW Weight2 and quality grade
1Values are reported as a ratio of the sample protein to an internal standard sample 2LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg ab Means with different superscripts differ (P < 0.05)
119
Figure 4.6 Means (± SE) for the abundance of the 30 kDa troponin-T degradation product in the longissimus lumborum from USDA Select (Se) and low Choice (LC) beef carcasses 2
1.8 a a 1
T 1.6 - b 1.4 1.2 1 0.8 0.6
Ratio of Ratio troponin 0.4 0.2 0 5 10 14 Aging day
1Values are reported as a ratio of the sample protein to an internal standard sample ab Means with different superscripts differ (P < 0.05)
120
Figure 4.7 Significant effects for the 30 kDa troponin-T degradation product in the semitendinosus from USDA Select (Se) and low Choice (LC) beef carcasses 1.4 a
1.2
1 T - 1 a 0.8 0.6 b 0.4
Ratio of Ratio troponin 0.2 0 5 10 14 Aging day
1Values are reported as a ratio of the sample protein to an internal standard sample ab Means with different superscripts differ (P < 0.05)
121
Figure 4.8 Representative Western blot of desmin. Samples were run on 10% SDS-PAGE gels and transferred to PVDF membrane. Membranes were blocked with a 0.5% non-fat dry milk solution, then incubated overnight at 4°C in a desmin antibody (1:80,000). Goat- anti rabbit was used as the secondary antibody (1:20,000)
35 kDa
122
Figure 4.9 Means (± SE) for the abundance of the 35 kDa desmin degradation product by a) hot carcass weight and b) aging day in the serratus ventralis from USDA Select and low Choice carcasses
A 1.4 a 1.2 a 1 1 0.8 b 0.6
0.4 Ratio of Ratio desmin 0.2 0 LW MW HW Weight2
B 1.6 1.4 a
1 1.2 a 1 0.8 b 0.6
Ratio of Ratio desmin 0.4 0.2 0 5 10 14 Aging day
1Values are reported as a ratio of the sample protein to an internal standard sample 2LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg ab Means with different superscripts differ (P < 0.05)
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Figure 4.10 Means (± SE) for the abundance of the 35 kDa desmin degradation product in the longissimus lumborum from USDA Select (Se) and low Choice (LC) carcasses 2.5 a abc ab abc abcd abcd abc abc abe 2 abcf 1 bef beg defg Se 5 efg efg efg 1.5 fg Se 10 g 1 Se 14 LC 5 Ratio of Ratio desmin 0.5 LC 10 LC 14 0 LW MW HW Weight2
1Values are reported as a ratio of the sample protein to an internal standard sample 2LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-g Means with different superscripts differ (P < 0.05)
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Figure 4.11 Means (± SE) for the abundance of the 35 kDa desmin degradation product by: a) hot carcass weight and grade, and b) aging day in the semitendinosus from USDA Select (Se) and low Choice (LC) carcasses
A 1 a 0.9 a 0.8 1 ab ab 0.7 ab b 0.6 0.5 0.4 0.3 Ratio of Ratio desmin 0.2 0.1 0 Se LC Se LC Se LC LW MW HW Weight2 and quality grade
B 1.2 a
1 1 0.8 b
0.6
0.4 c Ratio of Ratio desmin 0.2
0 5 10 14 Aging day
1Values are reported as a ratio of the sample protein to an internal standard sample 2LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-c Means with different superscripts differ (P < 0.05)
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Chapter 5
Beef carcass weight influences sensory attributes of Denver cut, strip, and eye of round steaks
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Abstract
Tenderness and flavor are two of the most important sensory attributes contributing to a positive eating experience of meat products. Beef hot carcass weight
(HCW) has been shown to influence carcass temperature during chilling, color, Warner-
Bratzler shear force, and cook loss of steaks from the chuck, loin, and round primals. The objective of this study was to determine the impact of HCW (LW = light weight, 296–
341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg) on the sensory attributes of Denver cut (DEN), strip, and eye of round (EOR) steaks from
USDA Select and low Choice (LC) beef carcasses. Following a 26-h chilling period, muscles from subsample of USDA Select and LC carcasses were collected for analysis.
Steaks were aged 5, 10, or 14 days and assessed by a consumer sensory panel for tenderness, juiciness, off-flavor, flavor liking, texture liking, and overall liking. A HCW
× aging day interaction was observed for tenderness in LC DEN, LC strip, Select EOR, and LC EOR steaks (P < 0.05). A HCW effect was observed for steaks from Select DEN and Select strip steaks (P < 0.01). Steaks from MW carcasses were consistently ranked over steaks from LW carcasses for tenderness. In LC strip and LC EOR steaks, a HCW effect was observed for flavor-liking (P = 0.03), with steaks from MW carcasses having the highest scores, HW an intermediate, and steaks from LW carcasses having the lowest scores. A HCW × aging day interaction was observed for overall liking in LC strip steaks
(P = 0.03) and a HCW effect observed for overall liking in Select DEN and LC EOR steaks (P < 0.02). In general steaks from MW carcasses had the highest attribute scores and were consistently ranked with the highest overall liking scores. Steaks from HW carcasses were often an intermediate between LW and MW carcasses for sensory
127 attributes, indicated steaks from HW carcasses may still provide a positive eating experience for consumers.
Introduction
Internal carcass temperature during early postmortem chilling and rate of temperature decline can impact tenderization (Locker, 1960; Hertzman et al., 1993), flavor (Warner et al., 2014), and aroma (Locker and Daines, 1975). Heavy beef carcasses
(>400 kg) have been shown to have elevated temperatures during chilling and display slower chilling rates (Djimsa et al., 2019; Fevold et al., 2019; Lancaster et al., 2020). As reported in Chapter 4, higher carcass temperatures for a prolonged period of time during chilling could result in early proteolysis, affecting tenderness and juiciness of muscles.
Tenderness is the most important sensory attribute for consumers seeking a positive eating experience (Savell et al., 1987). In the last 20 years, flavor has been reported to be almost as important to consumers as tenderness (Neely et al., 1998;
O'Quinn et al., 2012). Flavor and juiciness can be impacted by several factors including the abundance of marbling (Savell et al., 1987; Neely et al., 1998). Many studies have been conducted to analyze the effect of marbling on sensory attributes of strip steaks
(longissimus lumborum), but few studies have been conducted on Denver cut (DEN; serratus ventralis) and eye of round (EOR; semitendinosus) steaks. Additionally, research on the effect of hot carcass weight (HCW) on sensory traits of beef muscles is limited. In the previous chapters, HCW was reported to influence sarcomere length in the semitendinosus, Warner-Bratzler shear force (WBSF), cook loss, and proteolysis, objective measurements that can be used to predict subjective sensory measurements.
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Steaks from middle weight carcasses (386-432 kg) were often an intermediate to light
(296-341 kg) and heavy weight carcasses (466-523 kg). Aging day also influenced
WBSF, cook loss, and proteolysis. From these data, it is hypothesized steaks from earlier aging days will have unfavorable consumer scores and middle weight carcasses will have similar consumer scores as steaks from light and heavy weight carcasses for sensory attributes of the DEN, strip, and EOR. The objective of this study was to investigate the influence of beef HCW on six sensory attributes of DEN, strip, and EOR steaks from
USDA Select and low Choice (LC) beef carcasses.
Materials and Methods
Carcass Selection and Sample Processing
Carcasses were selected as described in Chapter 3 at approximately 45 min postmortem based upon HCW [light (LW) = 296–341 kg; middle (MW) = 386–432 kg; heavy (HW) = 466–523 kg]. Following grading, a sub-sample of USDA Select and LC carcasses were collected and processed into subprimals, which were transported to the
South Dakota State University Meat Laboratory. Subprimals were trimmed of excess fat and fabricated into 2.54 cm thick steaks (Figure 5.1). The DEN was cut on the major seam. The first three steaks (1-3) were used from the dorsal side of the anterior portion for sensory. The loin was faced prior to slicing into strip steaks. Starting at the anterior end, the first three steaks (1-3) were used for sensory analysis. The EOR was bisected along the medial plane prior to slicing into steaks. Starting from the bisection, the first three steaks (1-3) of the anterior portion were used for sensory. Samples were vacuum
129 packaged (3 mm thickness; Koch Supplies, Inc., Riverside, MO); wet aged at 2–4C for
5, 10, or 14 d; and frozen at -20C.
Consumer Sensory Panels
Each panel had at least 100 participants recruited from students and staff of the
University of Minnesota. To prevent sensory fatigue, consumer sensory panels were conducted over six days, one day for each muscle and quality grade. Due to different participants used between Select and LC panels, direct comparisons between quality grades could not be made. All participants were compensated for their time. The
University of Minnesota’s Institutional Review Board approved all recruiting and experimental procedures (IRB STUDY00002408).
Participants received nine different steak samples for each of the treatments (LW,
MW, or HW; aged 5, 10, or 14 d) according to the procedures outlined by AMSA (2015).
Steaks were wrapped in aluminum foil and cooked in an electric oven at 177°C until an internal temperature of 71°C, was reached (approximately 30 minutes). Once the connective tissue and fat were removed, steaks were cut into 1 cm 1 cm 2.54 cm pieces. Cut steak samples were held in porcelain double boilers maintained at approximately 71°C. Each participant received two 1 cm 1 cm 2.54 cm pieces of steak per sample in lidded Styrofoam cups with the correlating 3-digit codes, water, and an expectorant cup. Samples served to participants were balanced for order and carryover effects. Using a Hedonic scale, consumers used the first piece to score flavor liking, texture liking, and overall liking (0 = greatest imaginable disliking, 120 = greatest imaginable liking; Figure 5.2a) and the second piece to score the intensity of tenderness,
130 juiciness, and off-flavor (0 = none, extremely tough or dry; 20 = extremely intense, tender, or juicy; Figure 5.2b). Sensory data were collected using the SIMS 2000 software program (Sensory Computer Systems, Berkeley Heights, NJ).
Statistical Analysis
Sensory data were analyzed using the MIXED procedure in SAS (v 9.4; SAS Inc.,
Cary, NC) for the effects of HCW, aging day, and their interactions. Order of sample presentation was included as a covariate and panelist included as a random effect.
Separation of least square means was completed using a Tukey-Kramer analysis at =
0.05.
Results and Discussion
The demographic statistics of the participants from each consumer panel are shown in Table 5.1. Participants were at least 18 years old, had no food allergies or sensitivities, and had consumed cooked beef steak at least annually.
Denver Cut Steaks
A HCW effect was observed for tenderness of Select DEN steaks (P < 0.0001;
Figure 5.3a). Steaks from LW carcasses were decreased tenderness compared to steaks from MW and HW carcasses. An aging day effect (P < 0.0001; Figure 5.3b) was also observed for tenderness in Select DEN steaks. Steaks aged 5 d were the least tender, 10 d steaks intermediate, and steaks aged 14 d were the most tender. A HCW effect (P <
0.0001) was observed for juiciness (Figure 5.3c), with steaks from HW carcasses being
131 the juiciest and steaks from LW carcasses being the least juicy. Aging day did not influence juiciness (P = 0.08; Table 5.2). A HCW (P < 0.01; Figure 5.3d) and aging day
(P < 0.01; Figure 5.3e) effect were observed for texture liking. Consumers scored steaks from MW carcasses higher for texture liking compared to steaks from LW carcasses (P <
0.01). Steaks aged 5 d had the lowest texture liking scores (P < 0.01). No HCW or aging day effect was observed for off-flavor (HCW: P = 0.86; aging day: P = 0.28; Table 5.2) or flavor liking (HCW: P = 0.09; aging day: P = 0.12; Table 5.2). A HCW effect was observed for overall liking (P = 0.02; Figure 5.3f). Steaks from MW and HW carcasses had higher overall liking scores compared to steaks from LW carcasses. Aging day did not influence overall liking of Select DEN steaks (P = 0.22; Table 5.2).
In LC DEN steaks, a HCW aging day interaction was observed for tenderness
(P < 0.0001; Figure 5.4a), juiciness (P < 0.0001; Figure 5.4b), and texture liking (P =
0.02; Figure 5.4c). Steaks from MW carcasses were more tender than steaks from LW carcasses after 5 d of aging (P = 0.01). By 10 d of aging, steaks from LW and MW carcasses were of equal tenderness and steaks from HW carcasses were the least tender.
However, at 14 d of aging, steaks from HW carcasses were the most tender (P < 0.05).
Juiciness scores were highest for MW and HW steaks aged 5 d, LW and MW steaks aged
10 d, and HW steaks aged 14 d (P < 0.05). Texture liking was rated lower at 5 d for HW compared to MW (P = 0.04). No significant differences were observed for off-flavor
(HCW: P = 0.11; aging day: P = 0.52; Table 5.3), flavor liking (HCW: P = 0.37; aging day: P = 0.91; Table 5.3), or overall liking (HCW: P = 0.83; aging day: P = 0.53; Table
5.3).
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Previous research has not reported differences between weight groups in the serratus ventralis muscle for ultimate pH or sarcomere length, which are factors that can influence tenderness and juiciness (Melody et al., 2004; Chapter 4), or Warner-Bratzler shear force (Chapter 4). In the current study, consumers were able to detect differences for tenderness and juiciness in Select and LC DEN steaks from different weight groups.
Miller et al. (2001) reported steaks with similar WBSF values can have different tenderness scores based upon the juiciness of individual steaks. Termed the “halo effect,” consumers often rate one sensory attribute based off of the effect of another sensory attribute (Roeber et al., 2000; Corbin et al., 2015), explaining why differences were not detected with WBSF for tenderness, but consumers detected tenderness differences between weight groups. Additionally, timing between resting, cutting of steaks into sample pieces, and holding time in the double broilers, could contribute to juices lost, impacting both tenderness and juiciness.
Strip Steaks
In Select strip steaks, a HCW aging day interaction was observed for juiciness
(P = 0.02; Figure 5.5c) and texture liking (P = 0.01; Figure 5.5e). Steaks from HW carcasses aged 5 d had lower juiciness scores compared to steaks from MW carcasses aged 5 d (P < 0.01) and HW carcasses aged 14 d (P < 0.01). Juiciness of steaks from LW carcasses had a lower rating than steaks from HW carcasses after 14 d of aging (P <
0.01). Texture liking of strip steaks aged 5 d from HW carcasses was lower than steaks aged 5 d from MW carcasses (P = 0.01) and steaks aged 10 d and 14 d from HW carcasses (P < 0.01). A HCW (P < 0.01; Figure 5.5a) and aging day (P = 0.02; Figure
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5.5b) effect were observed for tenderness in Select strip steaks. Steaks from MW carcasses were more tender than steaks from LW and HW carcasses. Steaks aged 10 d were more tender than steaks aged 5 d and 14 d. An aging day effect was observed for flavor liking (P = 0.01; Figure 5.5d). Steaks aged 10 d had the highest scores, 14 d were intermediate, and 5 d aged steaks had the lowest scores. Hot carcass weight did not influence flavor liking (P = 0.73; Table 5.4). No significant differences were observed for off-flavor (HCW: P = 0.42; aging day: P = 0.57; Table 5.4). An aging day effect was observed for overall liking (P < 0.01; Figure 5.5f), which was highest at 10 d of aging, intermediate at 14 d, and lowest at 5 d of aging. Hot carcass weight did not influence overall liking (P = 0.28; Table 5.4).
A HCW aging day interaction was observed for tenderness (P < 0.01; Figure
5.6a), juiciness (P = 0.01; Figure 5.6b), texture liking (P < 0.01; Figure 5.6d), and overall liking (P = 0.03; Figure 5.6e) in LC strip steaks. Steaks from LW carcasses aged 5 d were less tender than all other weight groups and aging days (P < 0.02). Light weight steaks aged 10 d were more tender than 5 d HW, 10 d HW, 14 d LW, and 14 d HW (P < 0.05).
Consumers scored steaks from LW carcasses aged 10 d higher for juiciness than steaks aged 5 d or 10 d (P < 0.04). Steaks from LW carcasses aged 5 d had lower texture liking scores than steaks from MW carcasses aged 5 d (P = 0.02). Steaks from HW carcasses aged 10 d had lower texture liking scores than steaks from 10 d LW carcasses (P < 0.01).
For overall liking, steaks from LW carcasses were scored higher at 10 d compared to 5 d and 14 d (P < 0.01). Additionally, after 5 d of aging, steaks from MW carcasses were rated higher than 5 d LW carcasses (P = 0.02). After 10 d of aging LW carcasses were rated higher than 10 d HW carcasses (P = 0.03) for overall liking. A HCW effect was
134 observed for flavor liking (P = 0.03; Figure 5.6c). Steaks from MW carcasses had higher scores for flavor liking compared to steaks from LW carcasses. Aging day did not impact flavor liking (P = 0.74; Table 5.5). No HCW or aging day effect was observed for off- flavor in LC strip steaks (HCW: P = 0.42; aging day: P = 0.73; Table 5.5).
Aging day and HCW influenced some consumer scores of sensory attributes for strip steaks. Postmortem aging results in tenderization and the development of flavors and aroma (Smith et al., 1978; Resconi et al., 2013; Kim et al., 2016). Consumers were able to detect decreased tenderness for strip steaks from LW carcasses compared to heavier carcasses, especially at 5 d of aging. By 14 d, consumers had similar scores for
LC strip steaks. Djimsa et al. (2019) reported no differences for tenderness in strip steaks from light (less than the plant average) and heavy carcasses (greater than the plant average) from two plants in the U.S. The authors used a trained panel and the earliest sample used for sensory analyses was aged 14 d. Aging steaks for 14 d may be sufficient to minimize sensory differences between steaks, explaining why Djimsa et al. (2019) did not report a tenderness difference.
Eye of Round Steaks
In Select EOR steaks, a HCW aging day interaction was observed for tenderness (P = 0.01; Figure 5.7a) and juiciness (P = 0.01; Figure 5.7b). Steaks from HW carcasses aged 10 d were less tender compared to steaks from HW carcasses aged 5 d (P
< 0.01) and steaks from MW carcasses aged 5 d (P = 0.01) and 10 d (P = 0.04). Steaks from HW carcasses aged 14 d were less tender than steaks aged 5 d from HW carcasses
(P < 0.01) and steaks aged 14 d from MW carcasses (P < 0.01). Juiciness scores were
135 lower at 10 d compared to 5 d and 14 d of aging for steaks from HW carcasses (P <
0.0001). Juiciness scores were lower for 10 d HW compared to 10 d LW (P = 0.01) and
10 d MW (P = 0.04). Strip steaks aged 14 d from MW carcasses had higher juiciness scores than 14 d LW (P < 0.01) and 14 d HW (P = 0.03). An aging day effect was observed for texture liking (P = 0.02; Figure 5.7e). Steaks aged 5 d and 14 d had higher texture liking scores than 10 d (P < 0.03). Texture liking was not influenced by HCW (P
= 0.09; Table 5.6). An aging effect was observed for flavor liking (P = 0.02; Figure 5.7d).
Steaks aged 14 d were rated higher for flavor liking than steaks aged 10 d and 5 d aged steaks were intermediate. Hot carcass weight did not influence flavor liking (P = 0.29;
Table 5.6). A HCW effect was observed for off-flavor (P < 0.01; Figure 5.7c), with steaks from LW carcasses having higher scores than steaks from MW and HW carcasses.
Off-flavor was not influenced by aging day (P = 0.68; Table 5.6). An aging day effect was observed for overall liking (P = 0.01; Figure 5.7f). Overall liking was highest for steaks aged 5 d and 14 d. Overall liking was not influenced by HCW (P = 0.21; Table
5.6).
A HCW aging day interaction was observed for tenderness in LC EOR steaks
(P = 0.04; Figure 5.8a). Steaks from HW carcasses aged 10 d were more tender than those aged 14 d (P = 0.01). All steaks from LW carcasses were less tender compared to
MW and HW carcasses until 14 d of aging (P < 0.01). A HCW effect was observed for juiciness (P < 0.01; Figure 5.8b) and texture liking (P < 0.0001; Figure 5.8d), with MW and HW carcasses having the highest scores for both attributes. Neither juiciness nor texture liking were influenced by aging day (P = 0.49 and P = 0.47, respectively; Table
5.7). A HCW effect was observed for flavor liking (P = 0.03; Figure 5.8c). Flavor liking
136 was higher for MW carcasses compared to LW carcasses and steaks from HW carcasses were intermediate for flavor liking. No aging effect was observed for flavor liking (P =
0.23; Table 5.7). No HCW or aging day effect were observed for off-flavor (HCW: P =
0.51; aging day: P = 0.83; Table 7). A HCW effect was observed for overall liking of LC
EOR steaks (P < 0.01; Figure 5.8e). Steaks from MW carcasses had higher overall liking scores than LW and HW carcasses. No aging day effect was observed for overall liking
(P = 0.34; Table 7).
The EOR is a smaller round muscle that provides a more economical option for consumers in search of a nutrient-dense protein source. Literature is limited on the EOR due to its decreased tenderness and poorer eating experience compared to other round steaks, such as bottom round steaks. Steaks from LW and HW carcasses were less tender than MW carcasses. Previous research indicated shorter sarcomeres in HW carcasses, which could have been a result of the elevated temperatures observed during postmortem chilling (Locker and Hagyard, 1963; Chapter 3). Higher temperatures during early postmortem chilling can result in heat rigor and tougher products (Locker and Hagyard,
1963; Hertzman et al., 1993). Carcass weight did not influence overall liking of Select
EOR steaks, despite HCW impacting tenderness and juiciness, two of the top sensory attributes. Steaks from MW carcasses were scored higher for overall liking in LC EOR steaks. Juiciness, flavor liking, and texture liking of LC steaks were consistently higher for MW carcasses, indicating EOR steaks from LW or HW carcasses may result in a poor eating experience for the consumer. Luchak et al. (1998) reported no differences between
Select and Choice EOR steaks aged 10 days, suggesting a direct comparison of the two quality grades would not result in sensory differences.
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These data suggest HCW and aging day influence important sensory attributes of
Select and LC steaks. Marbling has been closely related to loin steak tenderness, accounting for 33% of the variation in loin steak tenderness, but marbling accounts for a small percentage of variation in other steaks, such as those from the round (Smith et al.,
1985). Therefore, assigning quality grades to other muscles off loin may not be a good predictor of the eating experience. While no direct comparison can be made between
Select and LC steaks in the current study, these data and previous research suggest LC steaks would have higher scores than Select steaks. Studies have consistently reported a more positive eating experience with upper 2/3 Choice and Prime loin steaks compared to
Select and LC loin steaks, but studies do not agree on the difference in eating quality between Select and LC steaks (Smith et al., 1985; Platter et al., 2003). Hunt et al. (2014) reported increased juiciness, flavor, and overall liking of upper 2/3 Choice DEN steaks over Select steaks aged 21 d. The authors used a greater difference in abundance of marbling between the two groups, but a higher quality grade is normally an indicator of an increased eating experience. Nyquist et al. (2018) reported increased consumer scores for juiciness and flavor for Choice DEN steaks compared to Select steaks, but no differences were reported for overall liking or acceptability for Choice and Select DEN steaks. Smith et al. (1985) reported no differences in tenderness of Select and LC strip steak, while Platter et al. (2003) and O'Quinn et al. (2012) reported LC steaks as being more tender than Select steaks. Neely et al. (1998) reported no differences between quality grade (ranging from low Select to top/high Choice) of strip steaks aged 14–21 d when asking consumers nation-wide to sample product. Luchak et al. (1998) reported no differences in juiciness or tenderness of 10 d aged Choice and Select strip steaks using a
138 trained sensory panel. Differences in steak preparation across studies and regional variation in consumer preferences may explain the inconsistencies observed for sensory attributes between Select and LC strip steaks.
Conclusion
Providing a positive beef eating experience for consumers is challenging with many antemortem and postmortem factors impacting the ultimate product. In the current study, HCW influenced the overall liking of Select DEN, LC strip, and LC EOR steaks.
Overall, steaks from MW carcasses had better scores than steaks from LW and HW carcasses. Carcasses lighter or heavier than MW carcasses, a representation of the industry average for beef carcasses, may not provide a positive eating experience for consumers. For some muscles, aging was sufficient to eliminate the differences consumers were detecting between the weight groups. Developing a better understanding of the development of flavor and aroma attributes during postmortem aging may help to reduce some of the differences observed between steaks across weight groups.
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Table 5.1 Consumer demographics
Gender Consumption Female Male Weekly Monthly Yearly Se1 Denver cut 78 31 58 50 1 LC1 Denver cut 77 27 61 41 2 Se1 strip 85 29 55 57 2 LC1 strip 78 26 54 47 3 Se1 eye of round 80 31 45 61 5 LC1 eye of round 76 28 45 57 2 1Se = USDA Select; LC = low Choice
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Table 5.2 Consumer sensory evaluations of USDA Select Denver steaks Weight1 LW MW HW SE P-value Off-flavor2 4.8 5.0 4.9 0.4 0.86 Flavor liking3 71.1 72.4 73.9 1.4 0.09
Aging day 5 10 14 Juiciness2 9.2 9.2 9.8 0.3 0.08 Off-flavor2 4.8 4.8 5.1 0.4 0.28 Flavor liking3 72.8 73.6 71.0 1.4 0.12 Overall liking3 71.0 73.1 72.6 1.4 0.22 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Intensity: 0 = none, extremely dry to 20 = extremely intense/juicy 3Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking
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Table 5.3 Consumer sensory evaluation of low Choice Denver steaks Weight1 LW MW HW SE P-value Off-flavor2 4.8 4.8 4.4 0.4 0.11 Flavor liking3 74.3 75.4 73.6 1.4 0.37 Overall liking3 74.0 74.3 73.5 1.4 0.73
Aging day 5 10 14 Off-flavor2 4.7 4.8 4.5 0.4 0.52 Flavor liking3 74.7 74.2 74.5 1.4 0.91 Overall liking3 73.3 73.7 73.5 1.4 0.83 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Intensity: 0 = none to 20 = extremely intense 3Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking
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Table 5.4 Consumer sensory evaluations of USDA Select strip steaks Weight1 LW MW HW SE P-value Off-flavor2 4.6 4.3 4.3 0.4 0.42 Flavor liking3 70.7 71.5 71.6 1.3 0.73 Overall liking3 69.5 71.4 70.5 1.3 0.28
Aging day 5 10 14 Off-flavor2 4.5 4.3 4.5 0.4 0.57 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Intensity: 0 = none to 20 = extremely intense 3Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking
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Table 5.5 Consumer sensory evaluations of USDA low Choice strip steaks Weight1 LW MW HW SE P-value Off-flavor2 4.1 3.8 4.0 0.4 0.42
Aging day 5 10 14 Off-flavor2 3.9 4.1 3.9 0.4 0.73 Flavor liking3 72.0 72.3 71.3 1.4 0.74 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Intensity: 0 = none to 20 = extremely intense 3Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking
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Table 5.6 Consumer sensory evaluations of USDA Select eye of round steaks Weight1 LW MW HW SE P-value 3 Flavor liking 65.0 66.8 66.7 1.4 0.29 3 Texture liking 63.4 66.2 63.6 1.6 0.09 3 Overall liking 64.2 66.5 64.7 1.5 0.21
Aging day 5 10 14 Off-flavor1 4.3 4.3 4.2 0.4 0.68 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Intensity: 0 = none to 20 = extremely intense 3Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking
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Table 5.7 Consumer sensory evaluations of USDA low Choice eye of round steaks Weight1 LW MW HW SE P-value Off-flavor2 4.4 4.1 4.3 0.4 0.51
Aging day 5 10 14 Juiciness2 7.5 7.7 7.8 0.3 0.49 Off-flavor2 4.3 4.2 4.2 0.4 0.83 Flavor liking3 68.4 69.8 67.6 1.5 0.23 Texture liking3 66.0 66.9 65.1 1.6 0.47 Overall liking3 67.7 68.8 66.8 1.6 0.34 1LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg 2Intensity: 0 = none, extremely dry to 20 = extremely intense/juicy 3Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking
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Figure 5.1 Diagram of steak location for a) Denver cut, b) strip, and c) eye of round muscles
A
B
C
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Figure 5.2 Sample consumer sensory scales for a) intensity ratings and b) liking ratings A)
B)
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Figure 5.3 Consumer sensory evaluation of USDA Select Denver steaks for a) tenderness by weight group, b) tenderness by aging day, c) juiciness, d) texture liking by weight group, e) texture liking by aging day, and f) overall liking. Two 1 cm x 1 cm x 2.54 cm cubes were used for sampling
A 12 a a b 10
1 8
6
4 Tenderness
2
0 LW MW HW Weight3
B 14 a 12 b c
1 10 8 6
Tenderness 4 2 0 5 10 14 Aging day
151
C 12 a 10 b c
1 8
6
Juiciness 4
2
0 LW MW HW Weight3
D 80 ab a 70 b
2 60 50 liking 40 30
Texture 20 10 0 LW MW HW Weight3
152
E 80 a a 70 b
2 60 50 liking 40 30
Texture 20 10 0 5 10 14 Aging day
F 80 a a b 70
2 60 50 liking 40 30
Overall 20 10 0 LW MW HW Weight3
1Intensity: 0 = extremely tough/dry to 20 = extremely tender/juicy 2Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking. 3LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-c Means with different superscripts differ (P < 0.05)
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Figure 5.4 Consumer sensory evaluation of USDA low Choice Denver steaks for a) tenderness, b) juiciness, and c) texture liking. Two 1 cm x 1 cm x 2.54 cm cubes were used for sampling
A 14 a bc b bcd bc bcde 12 e cde de
1 10 8 6
Tenderness 4 2 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
12 B a a a a ab 10 bc c c c
1 8 6
Juiciness 4 2 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
154
C 80 abcd abc ab abcd a bcd abcd cd d 70
2 60 50 40 30
Texture liking Texture 20 10 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
1Intensity: 0 = extremely tough/dry to 20 = extremely tender/juicy 2Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking 3LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-d Means with different superscripts differ (P < 0.05)
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Figure 5.5 Consumer sensory evaluation of USDA Select strip steaks for a) tenderness by weight, b) tenderness by aging day, c) juiciness, d) flavor liking, e) texture liking, and f) overall liking. Two 1 cm x 1 cm x 2.54 cm cubes were used for sampling
A 14 a 12 b b
10 1 8 6
Tenderness 4 2 0 LW MW HW Weight3
B 14 a 12 b b
10 1 8 6
Tenderness 4 2 0 5 10 14 Aging day
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C 10 9 a a ab a a ab a a 8 b b b b
1 7 6 5 4 Juiciness 3 2 1 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
D 80 a c b 70
2 60 50 40 30
Flavor liking Flavor 20 10 0 5 10 14 Aging day
157
E 80 a ab ab a a ab a 70 b b
2 60 50 40 30
Texture liking Texture 20 10 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
F 80 a b ab 70
2 60 50 40 30
Overall liking Overall 20 10 0 5 10 14 Aging day
1Intensity: 0 = extremely tough/dry to 20 = extremely tender/juicy 2Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking 3LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466– 523 kg a-c Means with different superscripts differ (P < 0.05)
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Figure 5.6 Consumer sensory evaluation of USDA low Choice strip steaks for a) tenderness, b) juiciness, c) flavor liking, d) texture liking, and e) overall liking. Two 1 cm x 1 cm x 2.54 cm cubes were used for sampling
14 a A ab ac ad cd bcd 12 d d e
1 10 8 6
Tenderness 4 2 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
B 12
10 a ab abc bd cd cd 1 8 d d d 6
Juiciness 4
2
0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
159
C 80 a b ab 70
60 2 50 40
30 Flavor liking Flavor 20 10 0 LW MW HW Weight3
D a 80 abc ab ad bd bd cd ad 70 d
2 60 50 40 30
Texture liking Texture 20 10 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
160
E 80 a abc ab abcd abc d cd abcd bcd 70
2 60 50 40 30
Overall liking Overall 20 10 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
1Intensity: 0 = extremely tough/dry to 20 = extremely tender/juicy 2Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking 3LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466–523 kg a-e Means with different superscripts differ (P < 0.05)
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Figure 5.7 Consumer sensory evaluation of USDA Select eye of round steaks for a) tenderness, b) juiciness, c) off-flavor, d) flavor liking, e) texture liking, and f) overall liking. Two 1 cm x 1 cm x 2.54 cm cubes were used for sampling
A 14 cd ac bc a d cd 12 cd ab cd
1 10 8 6
Tenderness 4 2 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
B 10 a b b 8 bcd bcd bc cd c 1 d 6 e
4 Juiciness 2
0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
162
C 6 a 5 b b
1 4
3
flavor -
Off 2
1
0 LW MW HW Weight3
D 80 a 70 ab b
60 2 50 40 30 Flavor liking Flavor 20 10 0 5 10 14 Aging day
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E 80 a a 70 b
2 60 50 40 30
Tesxture liking Tesxture 20 10 0 5 10 14 Aging day
F 80 a a 70 b
2 60 50 40 30
Overall liking Overall 20 10 0 5 10 14 Aging day
1Intensity: 0 = none, extremely tough/dry to 20 = extremely intense/tender/juicy 2Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking 3LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466– 523 kg a-e Means with different superscripts differ (P < 0.05)
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Figure 5.8 Consumer sensory evaluation of USDA low choice eye of round steaks for a) tenderness, b) juiciness, c) flavor liking, d) texture liking, and e) overall liking. Two 1 cm x 1 cm x 2.54 cm cubes were used for sampling
A 14 a a 12 ab abc ab bc cd cd 1 10 d 8 6
Tenderness 4 2 0 5 10 14 5 10 14 5 10 14 LW MW HW Weight3 and aging day
B 10 a a 8 b
1 6
4 Juiciness
2
0 LW MW HW Weight3
165
C 80 a 70 b ab
60 2 50 40 30 Flavor liking Flavor 20 10 0 LW MW HW Weight3
D 80 a a 70 b
2 60 50 40 30
Texture liking Texture 20 10 0 LW MW HW Weight3
166
E 80 a 70 b b
2 60 50 40 30
Overall liking Overall 20 10 0 LW MW HW Weight3
1Intensity: 0 = none, extremely tough to 20 = extremely intense/tender/juicy 2Likings: 0 = greatest imaginable dislike to 120 = greatest imaginable liking 3LW = light weight, 296–341 kg; MW = middle weight, 386–432 kg; HW = heavy weight, 466– 523 kg a-d Means with different superscripts differ (P < 0.05)
167
Chapter 6
Conclusions
168
These studies demonstrate heavy beef carcasses (≥465 kg) and improved quality grades influence internal temperature decline of carcasses during postmortem chilling.
Heavier carcasses had higher temperatures for the duration of chilling. The relationship between hot carcass weight and quality grade was variable as carcass weight increased and across muscles.
The higher carcass temperatures during chilling resulted in product quality differences. Heavy carcasses had higher L, a, and b values in the serratus ventralis, longissimus lumborum, and semitendinosus muscles than light carcasses (295–340 kg).
The lighter and redder steaks observed in heavy carcasses may favor consumer selection.
However, stability of the color of steaks from heavy carcasses is unknown.
Hot carcass weight influenced tenderization during the first 14 d postmortem.
Generally, steaks from light carcasses had increased Warner-Bratzler shear force values and decreased tenderization through 5 d of aging. By 14 d of aging, tenderness of steaks from light carcasses was similar to steaks from middle (386–431 kg) and heavy carcasses.
The aging process is important to providing consistent product in an industry challenged by producing consistent product.
Palatability of steaks is important to consumer selection and providing the consumer a positive eating experience. The sensory attributes assessed show the variable effects of HCW on sensory traits. Overall, steaks from middle weight carcasses had higher scores for overall liking across the three muscles. The middle weight group of carcasses represents the industry average for beef carcasses. With this weight group being favored for overall liking, continuing to allow light or heavy carcasses may result in undesirable sensory outcomes, especially at early aging days. Additional research is
169 required to understand how postmortem conditions of hot carcass weight impacts flavor and aroma development throughout the aging process.
Chilling systems are one of the highest energy costs of plants. Heavy and higher grading carcasses result in additional chilling time which could decrease chilling efficiency. These data can be used to help guide the beef industry regarding decisions to improve chilling systems and provide consistent, high-quality products.