Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 2001 Effect of dietary conjugated linoleic acid (CLA) on the fatty acid status in chicken and meat quality Min Du Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agriculture Commons, Animal Sciences Commons, and the Food Science Commons Recommended Citation Du, Min, "Effect of dietary conjugated linoleic acid (CLA) on the fatty acid status in chicken and meat quality " (2001). Retrospective Theses and Dissertations. 634. https://lib.dr.iastate.edu/rtd/634 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. 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Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. ProQuest Information and Learning 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600 Effect of dietary conjugated Iinoieic acid (CLA) on the fatty acid status in chicken and meat quality By Min Du A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Co-Majors: Meat Science; Food Science and Technology Program of Study Committee: Dong U. Ahn, Co-Major Professor Jane A. Love, Co-Major Professor Murray L. Kaplan Joseph G. Sebranek David G. Topel Iowa State University Ames, Iowa 2001 UMI Number 3034178 UMI® UMI Microform 3034178 Copyright 2002 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 ii Graduate College Iowa State University This is to certify that the doctoral dissertation of Min Du has met the dissertation requirements of Iowa State University Signature was redacted for privacy. Co-Major Professor Signature was redacted for privacy. Co-Majo P fessor Signature was redacted for privacy. e Co-MajMajor Program Signature was redacted for privacy. or the C Major Pr iii TABLE OF CONTENTS CHAPTER 1. GENERAL INTRODUCTION 1 Dissertation Organization 3 CHAPTER 2. LITERATURE REVIEW 4 Part L Biological Functions of Conjugated Linoleic Acid 4 Part II. Effect of Dietary CLA and Irradiation on the Flavor, Lipid Oxidation, and Color of Poultry Meat 21 References 33 CHAPTER 3. EFFECT OF DIETARY CONJUGATED LINOLEIC ACID (CLA) ON THE GROWTH, FAT ACCUMULATION AND MEAT QUALITY OF BOILERS 51 Abstract 51 Introduction 51 Materials and Methods 53 Results and Discussion 56 References 58 CHAPTER 4. EFFECT OF DIETARY CONJUGATED LINOLEIC ACID ON THE COMPOSITION OF EGG YOLK LIPIDS 67 Abstract 67 Introduction 67 Materials and Methods 69 Results and Discussion 71 References 75 CHAPTER 5. EFFECT OF DIETARY CONJUGATED LINOLEIC ACID (CLA) AND LINOLEIC: LINOLENIC ACID RATIO ON POLYUNSATURATED FATTY ACID STATUS IN LAYING HENS 84 Abstract 84 Introduction 85 iv Materials and Methods 86 Results and Discussion 88 References 93 CHAPTER 6. EFFECT OF DIETARY CONJUGATED LINOLEIC ACID, IRRADIATION, AND PACKAGING CONDITIONS ON THE QUALITY CHARACTERISTICS OF RAW BROILER BREAST FILLETS 103 Abstract 103 Introduction 103 Materials and Methods 104 Results and Discussion 106 Conclusions 109 References 110 CHAPTER 7. INFLUENCE OF DIETARY CONJUGATED LINOLEIC ACID ON VOLATILE PROFILES, COLOR AND LIPID OXIDATION OF IRRADIATED RAW CHICKEN MEAT 119 Abstract 119 Introduction 120 Materials and Methods 121 Results and Discussion 123 Conclusions 126 References 127 CHAPTER 8. VOLATILE PROFILES AND LIPID OXIDATION OF IRRADIATED COOKED CHICKEN MEAT FROM LAYING HENS FED WITH DIETS CONTAINING CONJUGATED LINOLEIC ACID 140 Abstract 140 Introduction 141 Materials and Methods 142 Results and Discussion 144 References 147 V CHAPTER 9. QUALITY CHARACTERISTICS OF IRRADIATED CHICKEN BREAST ROLLS FROM BROILERS FED DIFFERENT LEVELS OF CONJUGATED LINOLEIC ACID 157 Abstract 157 Introduction 157 Materials and Methods 158 Results and Discussion 162 Conclusions 165 References 165 CHAPTER 10. GENERAL CONCLUSION 174 VITA 177 ACKNOWLEDGEMENTS 178 1 CHAPTER 1. GENERAL INTRODUCTION Conjugated Iinoieic acid (CLA) has been shown to have a variety of biological effects. Modulating lipid metabolism seems to be the main effect of CLA in vivo. Other effects of CLA on health, such as anti-cancer, anti-artherosclerosis and improving immuno-responses, might be derived or partially derived from the alternated lipid metabolism after CLA feeding. Up to now, most of studies on the effect of CLA on fat metabolism are concentrated on rats, mice, pigs and other mammals, and there are seldom reports on birds. Considering the differences in lipid metabolism between birds and mammals, results from the studies of mice and other mammals cannot be safely extrapolated to birds. Thus studies on the effectiveness of CLA on lipid metabolism in birds are needed. In birds, liver is the principal site of lipid synthesis and has very high capacity for de novo lipid biosynthesis. And, unlike mammals, fatty acids (not glucose) are the main energy source for birds. All of these facts make birds a distinct model for studying lipid metabolism. Further, yolk lipid is directly derived from lipids exported from liver. Therefore, analysis of yolk lipid composition changes after CLA feeding can reflect the lipid metabolism in the liver of birds quite well. Therefore, we chose laying hens as a model to study the effect of CLA on the fatty acid status in vivo, mainly through analyzing the change in yolk fatty acid composition after CLA feeding. Several studies suggested that CLA could reduce fat accumulation in mammals. CLA was suggested to promote muscle growth and reduce fat deposition in mice (Delany et al., 1999), improve feed efficiency in rats (Park et al, 1997; Chin et al, 1994), and loin quality in pigs (Dugan et al., 1999). There are no published reports about the effect of CLA on fat accumulation in birds. Thus, we studied the effect of dietary CLA on the growth and lipid status in chickens. CLA has been shown to inhibit the activity of stearoyl-CoA reductase (Park et al., 1999b). CLA also reduced the content of arachidonic acid. Since arachidonic acid, and eicosapentaenoic acid (EPA) and docosahexenoic acid (DHA) are synthesized by different pathways, reducing the synthesis of arachidonic acid may not mean reducing that of EPA and DHA. We assessed this hypothesis by feeding hens with diets of different n-3/n-6 fatty acid 2 ratios. The biological effect of CLA could relate to its ability to alter the synthesis of arachidonic acid and EPA. Meats have pleasant flavor for most people. This is due to the highly desirable taste and aroma of meats. While the tastes of meats are relatively stable and constant, the aroma of meats is unstable and tends to form off-odors. Off-odors developed in meat products cause large losses in the meat industry, and are unsolved problems worldwide (Melton, 1983). Especially, in the USA, due to the application of irradiation in the meat industry, irradiation odor, which is a sweet, cooked-corn like off-odor, causes even more serious challenges. And thus many studies were conducted on identifying, illustrating, and preventing those off-odors. The off-odor formation in meats is closely related to lipid oxidation. Warmed-over flavor is a typical off-odor resulting from lipid oxidation. The progress and degree of lipid oxidation are correlated with unsaturated fatty acid content in meat. Poultry meat contains more polyunsaturated fatty acids (PUFA) than red meat, which exaggerates the problem associated with lipid oxidation. Dietary CLA has been reported to reduce the content of unsaturated fatty acids in lipids (Du et al., 1999; 2000a; 2001b). Therefore, poultry meats from birds fed CLA may be less susceptible to lipid oxidation. However, CLA itself may participate in the flavor or off-odor formation, and other aspects of meat quality, such as color and texture. Up to now, few studies were done in this area, none in poultry, and therefore it is important to analyze the effect of CLA on meat quality. Irradiation treatment has been proposed as an effective way to control bacteria contamination and lengthen the shelf-life of foods (Parkas, 1998). On the same time, ionizing radiation generates free radicals that may cause lipid peroxidation and other chemical changes, and influence the quality of meats (Ahn et al., 2000ab). The presence of CLA and also the reduced unsaturated fatty acid content in meat could alter the oxidative stability of meat, and thus influence irradiation induced changes in volatiles and color.