Original Paper Investigation of Physicochemical and Textural

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Original paper

Investigation of Physicochemical and Textural Characteristics and Volatile Compounds of Kazakh Dry-cured Beef

1 2 3* 3 4 3 3 Kun Sha , Ze-Jun Zhang , Bao-Zhong Sun , Hai-Peng Li , Huan-Lu Song , Yu-Miao Lang , Yuan-Hua Lei , 5 5* Hong-Do Li and Yang Zhang

1College of Food and Wine, Yantai Research Institute of China Agricultural University, Yantai 264670, P.R. China 2College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P.R. China 3Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. China 4Beijing Key Laboratory of Flavor Chemistry, Beijing Technology and Business University, Beijing 100048, P.R. China 5Animal Science Academy of Xinjiang Uygur Autonomous Region, Urumqi 830000, P.R. China

Received November 14, 2016 ; Accepted February 4, 2017

The aim of this study was to evaluate the physicochemical and textural characteristics and volatile compounds of Kazakh dry-cured beef made in China. Two types of Kazakh dry-cured beef were investigated: Kazakh dry- cured beef made with smoking and spices (T1) and without smoking and spices (T2). There were significant (P

< 0.05) differences in values of aw, moisture, L*, cohesiveness and chewiness between the two types. A total of 86 volatile compounds were isolated by solid phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS). Hydrocarbons were the most abundant in T1 products and aldehydes in T2 products. Principal component analysis showed that the first principal component (PC1) was highly related to smoke derivatives— naphthalene, 2-cyclopenten-1-one derivatives, 4-methyl-4-hepten-3-one, acetophenone, 2,3-dihydro-1H-Inden-1-one, 2-furanmethanol, methoxy-phenyl-oxime, furfural, 1-(2-furanyl)-ethanone and phenols—and the second principal component (PC2) to lipid derivatives—straight-chain aliphatic aldehydes, methyl ketone, straight-chain alcohols and 2-pentyl-furan.

Keywords: Kazakh dry-cured beef, physicochemical properties, texture profile, volatile compounds

Introduction Węsierska et al., 2014). Dry-cured beef, a type of product made from beef cuts, is Kazakh dry-cured beef is a popular traditional meat product processed by curing and drying. Many types of dry-cured beef, from the Xinjiang Uygur Autonomous Region of Northwestern produced in different countries and regions including Italian China with its distinctive nomadic features. It is an important part bresaola (Paleari et al., 2000), Brazilian Charqui (Youssef et al., of Kazakh food culture connecting the nation’s history to the 2007), Turkish pastirma (Kaban, 2009), and Spanish cecina present day. Manufacturing traditional Kazakh dry-cured beef is (Molinero et al., 2008), are favored by consumers. The type of simple and consists of three stages: cutting up the meat followed muscle used, the processing technology as well as its geographical by salting and air-drying. Once dried, the meat is sometimes origin can lead to different quality characteristics of these dry- smoked. Unlike other dry-cured beef or ham products with longer cured meat products (Sánchez-Peña et al., 2005; Toldrá, 2006; ripening times (Molinero et al., 2008; Pugliese et al., 2015),

*To whom correspondence should be addressed. E-mail: Sun B. ; [email protected] Zhang Y. ; [email protected] 376 K. Sha et al.

Kazakh dry-cured beef is generally manufactured without any analysis. ripening stage. Kazakh dry-cured beef is traditionally made with a Physicochemical analysis Water activity (aw) was measured variable processing time depending on the size of the cut of meat using a portable water activity meter (HygroPalm AW1, Rotronic used and the climatic conditions prevailing during the drying stage. AG, Bassersdorf, Switzerland). The meat color was assessed using In Xinjiang, it is made mainly during winter in a climate of low a portable colorimeter (CR-400, Konica-Minolta Sensing Inc., temperature and low humidity. Special geographical conditions and Osaka, Japan) using CIELAB space (CIE, 1976). Lightness (L*), unique production methods combine to form the unique flavor and redness (a*) and yellowness (b*) were measured after exposing the chewy texture of Kazakh dry-cured beef, which has become a meat samples to air for 30 min. The pH was determined using a characteristic regional food important for tourism in Xinjiang. At pH-meter (IQ160, Spectrum Technologies Inc., Fort Worth, Tex., present, most Kazakh dry-cured beef is produced in family USA). The protein, fat, moisture and NaCl contents were analyzed workshops or on a small scale in plants with no standard production according to ISO methods 937:1978 (ISO, 1978), 1443:1973 (ISO, methods. Scientific research on Kazakh dry-cured beef has just 1973), 1442:1997 (ISO, 1997) and 1841:1996 (ISO, 1996). Each begun. Sha et al. (2016) have investigated changes in lipid test sample was measured three times and the results were oxidation, fatty acid profile and volatile compounds of traditional averaged. Kazakh dry-cured beef during its processing and storage. Texture profile analysis (TPA) Meat samples were placed in a Information about quality characteristics of different types of retort pouch and heated in a boiling water bath until a core- Kazakh dry-cured beef is scarce, and is required for its industrial temperature of 70℃ was attained. After cooling to room production. temperature (22℃), four meat cubes, 1 × 1 × 1 cm, were taken The objectives of the present study are therefore to investigate from each sample then used for instrumental texture analysis. the physicochemical and textural characteristics and volatile TheTPA was performed using a texture analyzer (TA-XT plus, compounds of 30 samples of Kazakh dry-cured beef produced in Stable Micro Systems, Godalming, UK). A two-cycle compression China’s Xinjiang region. Principal component analysis will be used test was carried out using a cylindrical probe (35 mm diameter) at to distinguish the differences in volatile flavor compounds between 75% compression using a pre-test speed of 2 mm/s, a test speed of the samples. 1 mm/s and a post-test speed of 2 mm/s. Six texture parameters, obtained from the force-time curve: hardness (kg), springiness, Materials and Methods cohesiveness, gumminess, chewiness (kg) and resilience, were Samples 30 Kazakh dry-cured beef production were purchased calculated using the Texture Expert software (Stable Micro from 10 different producers for sale in three main production Systems). regions of Xinjiang, China: Altay City, Ili Kazakh Autonomous Volatile compounds analysis SPME-GC/MS was used to Prefecture and Tower City. Three individually wrapped products analyze the volatile compounds in the meat sample. Six g of were purchased from the same producer. Detailed information on ground meat samples were placed in a 20-mL sample vial and the raw meat characteristics and the processing conditions for sealed with a septum. The vial was placed in a water bath at 50℃ Kazakh dry-cured beef production were obtained from each to equilibrate for 20 min then an SPME fiber (50/30 μm carboxen/ producer at the time of purchase. Based on the production process, divinylbenzene/polydimethylsiloxane, Supelco, Bellefonte, Pa., 30 samples of Kazakh dry-cured beef were divided into two types: USA) was inserted into the headspace for extraction for 40 min at those made by smoking with spices (T1) and those made without 50℃. The fiber was then injected into a 7890A-7000B GC-MS smoking or spices (T2). Grass-fed cow or steer meat has been (Agilent Technologies Inc., Santa Clara, Calif., USA) for considered most suitable for making Kazakh dry-cured beef desorption for 7 min at 250℃. The volatile compounds were because of its unique flavor and chewy texture. The production separated using a DB-WAX capillary column (30 m × 0.25 mm × process was generally as follows: the raw meat was cut into strips 0.25 μm, J & W Scientific, Folsom, Calif., USA). The GC was (thickness ~ 3 cm, width ~ 5 cm) along the direction of the smooth operated in split mode (5:1) with a column flow rate of 6 mL/min. muscle fibers. For the T1 products, the meat strips were treated The temperature program was: 40℃ for 3 min, heating to 200℃ at with salt and a mixture of spices (pepper, fennel, parsley and 5℃/min, heating to 230℃ at 10℃/min and finally kept at 230℃ geraniol) for 24 _ 48 h at 0 _ 4℃, while only salt was used for the for 3 min. The GC/MS interface was set at 250℃. The MS T2 products. After salting, the meat strips were hung in a clean operating conditions were: electron energy, 70 eV; interface ventilated environment to dry for 2 _ 4 d at 0 _ 12℃ and temperature, 250℃; transfer line temperature, 280℃; ion source 35% _ 55% relative humidity. For making T1 products only, the temperature, 230℃; quadrupole temperature, 150℃; and scan meat strips were transferred to the smoking room at 60 _ 80℃ until range, m/z 55 _ 500. the meat surface had hardened and become dark red. For T2 The volatiles were identified by matching their mass spectra products, this step was omitted. All samples were purchased in with those in the NIST mass spectra libraries and by comparing the December, then vacuum-packed and stored at _80℃ until further retention indices (IR) with those reported in the literature. The IR Characteristics of Kazakh Dry-cured Beef 377

Table 1. Physico-chemical and texture parameters in two types of Kazakh dry-cured beef. SEM: Standard error of the mean.

T1 (n=12) T2 (n=18) SEM P-level CV% (n=30) pH 5.85 5.72 0.05 NS 5.15

aw 0.92 0.94 0.00 * 2.56 Moisture (g kg−1) 564.76 615.21 0.01 * 13.53 Fat (g kg−1) 43.10 36.53 0.01 NS 84.41 Protein (g kg−1) 308.58 290.33 1.12 NS 20.68 NaCl (g kg−1) 47.91 39.82 0.31 NS 39.51 L* 36.66 32.33 0.96 * 15.37 a* 12.11 11.18 0.67 NS 31.61 b* 7.47 7.45 0.39 NS 28.29 Hardness (kg) 10.39 6.42 1.20 NS 82.21 Springiness 0.41 0.39 0.01 NS 15.96 Cohesiveness 0.46 0.42 0.01 * 11.68 Gumminess (kg) 5.16 2.77 0.68 NS 99.88 Chewiness (kg) 2.45 1.11 0.38 * 125.41 Resilience 0.19 0.18 0.01 NS 26.25

P-level: Level of significance found by analysis of variance. NS, not significant; *, P < 0.05. was calculated in relation to the retention time of n-alkane value of 0.75 which confers microbial stability on meat products _ standards (C7 C23) (Supelco, Sigma-Aldrich, St. Louis, Mo., stored at room temperature (Leistner, 1987). Therefore, Kazakh

USA). The internal standard method was used for quantifying the dry-cured beef can be considered as a “perishable” product with aw volatiles. 2-methyl-3-heptanone (1 μL, 0.41 mg/mL) was added to values ranging of 0.95 _ 0.91, so must be stored at or below 10℃ the samples at the same time as the internal standards. The results (Leistner and Roedel, 1975). The mean moisture contents were in were expressed as ng/g of dry matter. The concentration for each the range of 564.76 _ 615.21 g kg−1 (CV = 13.53%), higher than compound was calculated as follows: those of other dry-cured beef products: Turkish pastirma, 466.1 _ 479.6 g kg−1 (Ceylan and Aksu, 2011); and Spanish Cecina Concn(i)=Area(i)×0.41×1000/Area(j)×sample weight(dry matter) ······Eq. 1 _ −1 de León, 501.1 601.4 g kg (Molinero et al., 2008). The mean aw where Concn (i) was the concentration of a compound; Area (i) and moisture values in T1 products were significantly lower the area of a compound on the chromatogram; and Area (j) the area (P < 0.05) than in T2 products, because of differences in the extent of the internal standard on the chromatogram. of drying during the smoking process. Statistical analysis The physicochemical, textural and volatile The mean protein contents were 290.33 (T2) and 308.58 (T2) g compounds data were analyzed by one-way analysis of variance kg−1 (CV = 20.68%). This value was similar to that reported for using version 19.0 of the SPSS statistics software (SPSS, Chicago, bresaola (319.6 g kg−1) (Paleari et al., 2000), but higher than that Ill., USA). The mean values were compared using Duncan’s for Charqui (263 g kg−1) (Youssef et al., 2007). The mean fat multiple range test at a significance level of P < 0.05. The Pearson contents of 36.53 (T2) and 43.10 (T1) g kg−1 were higher than correlation analysis was used to evaluate the relationships between those of bresaola (17.425.0 g kg−1) (Paleari et al., 2000; Youssef et the variables. Data obtained by SPME-GC/MS were analyzed by al., 2007). A higher CV of 84.41% was observed for fat content principal component analysis (PCA) to evaluate differences in the overall. The mean NaCl contents were 39.82 (T2) and 47.91 (T1) g volatile profiles of the two types of Kazakh dry-cured beef. kg−1 with a CV of 39.51%. There were no significant differences between the two types of samples regarding protein, fat and NaCl Results and Discussion content (P > 0.05). A Pearson correlation analysis showed that the Physico-chemical and texture properties Table 1 shows the protein and NaCl contents were significantly negatively correlated physicochemical and textural characteristics of the two types of with moisture content (r = _0.785** and r = _0.453*, respectively, _ _ Kazakh dry-cured beef. The mean pH values were 5.72 (T2) and P < 0.05) and aw (r = 0.746** and r = 0.426*, respectively,

5.85 (T1) with low coefficients of variation (CV = 5.15%) which P < 0.05). were close to those reported for other dry-cured beef products (pH Regarding color parameters, the mean L*, a*and b* values for 5.72 _ 5.95) (Paleari et al., 2000; Molinero et al., 2008; Ceylan and T2 and T1 were 32.33 and 36.66, 11.18 and 12.11 and 7.45 and Aksu, 2011). 7.47, respectively. The L* values in T1 products were significantly

The mean aw values were 0.92 (T1) and 0.94 (T2) and a low higher than in T2 products (P < 0.05). The mean a* value had a overall CV of 2.56%. These values were higher than the critical aw higher CV (31.61%) than L* (CV = 15.37%) and b* (CV = 378 K. Sha et al.

28.29%). This indicated a visually inconsistent red color among the were detected only in the T1 products, perhaps originating from samples. This may have been related to the high variability in fat added spices such as pepper and paprika (Ansorena et al., 2001; content, which was significantly negatively correlated (r = _0.487, Kaban, 2009; Marušić et al., 2014). Naphthalene, an aromatic P < 0.05) with a*. hydrocarbon found only in the T1 products, has been identified as The texture parameters from TPA showed extremely high being related to the smoking process (Muriel et al., 2004). coefficients of variation (11.68 _ 125.41%). These results Although D-limonene has been associated with animal feedstuffs, illustrated the variability in the processing technology and it has mainly been attributed to the added spices used in the conditions used by the producers of Kazakh dry-cured beef preparation of dry-cured products (Ansorena et al., 2001). products on the market which has led to very different texture Therefore, the higher levels of hydrocarbons found in T1 products profiles. There were significant differences (P < 0.05) in were mainly related to the use of spices with a higher content of cohesiveness and chewiness between the two types of samples, terpenes. Compared with aliphatic hydrocarbons, aromatic with no significant differences (P > 0.05) found in hardness, hydrocarbons and terpenes have lower threshold values and make springiness, gumminess and resilience. The T1 products showed an important contribution to the flavor of dry-cured meat products higher cohesiveness and chewiness values than the T2 products. (Ramírez and Cava, 2007; Kaban, 2009). Volatile compounds A total of 86 volatile compounds were Aldehydes have very low flavor threshold values and play an identified and quantified in the two types of Kazakh dry-cured beef important role in the formation of the flavor of dry-cured products (Table 2). The volatile classes comprised 21 hydrocarbons, 10 (Purriños et al., 2011; Marušić et al., 2014; Pugliese et al., 2015). aldehydes, 15 ketones, 15 alcohols, five nitrogenous, four furans, The straight-chain aliphatic aldehydes (hexanal, heptanal, octanal, two esters, two ethers, and 12 phenols. Seventy-three volatile (Z)-2-heptenal, nonanal, (E)-2-octenal, decanal, and (E)-2-nonenal) compounds were detected in the T1 products and 36 in the T1 detected are typical products of lipid oxidation (Purriños et al., products. Only 23 volatile compounds were detected in both T1 2011), while branched aldehydes such as 3-methyl-butanal and and T2 products: hydrocarbons (10), aldehydes (6), alcohols (6), 4-(1-methylethyl)-benzaldehyde could derive from Strecker and furans (1). degradation reactions of amino acids (Muriel et al., 2004). The profiles of volatile compounds were very different between Aldehydes were present at relatively high levels in T2 products the two types of samples. The volatile composition in the T1 compared with T1 products, the difference in quantity not being product was: hydrocarbons (1645.99 ng/g), phenols (1104.68 ng/g), significant P( > 0.05). alcohols (474.89 ng/g), ethers (452.24 ng/g), aldehydes (307.81 ng/ In the present study, ketones showed larger differences between g), ketones (284.94 ng/g), nitrogenous (135.75 ng/g), furans the two types of samples both in kind and quantity. 4-Methyl (135.51 ng/g), and esters (18.78 ng/g). The major compounds ketones (2-pentanone, 2-octanone, 2, 3-octanedione, and present were: caryophyllene, phenol, 2-methoxy-phenol, 2-nonanone) were detected only in T2 products. They have also eucalyptol, D-limonene, and nonanal. Similarly, hydrocarbons been found in other dried meats (Hierro et al., 2004; Marušić et al., were reported as the dominant volatiles in Turkish pastirma 2014), and could originate from the oxidation of lipids (auto- (Kaban, 2009). In contrast, the volatile composition of the T2 oxidation or mould metabolism) (Muriel et al., 2004). 2-Pentanone, product was: aldehydes (573.22 ng/g), alcohols (323.32 ng/g), 2-octanone, and 2-nonanone characterize the typical aroma of blue hydrocarbons (292.17 ng/g), ketones (74.98 ng/g), and furans cheeses and fruity aromas (García-González et al., 2008). Their (29.32 ng/g).The major compounds present were: nonanal, hexanal, absence in T1 products may be related to the smoking process, 1-octen-3-ol, octanal, 1-hexanol, and heptanal. The results were in where antioxidants such as phenols can be formed which prevent agreement with those reported by Sha et al. (2016) for Kazakh dry- the auto-oxidation of lipids (Jerković, 2010). Eight 2-cyclopenten- cured beef. In other dry-cured hams (Purriños et al., 2011; Marušić 1-one derivatives (2-methyl-2-cyclopenten-1-one, 2,3-dimethyl-2- et al., 2014; Pugliese et al., 2015), aldehydes were also found to be cyclopenten-1-one, 3,4-dimethyl-2-cyclopenten-1-one, the most abundant compound, whereas esters were the 2,3,4-trimethyl-2-cyclopenten-1-one, 3-methyl-2-cyclopenten-1- majorcompounds found in dry-cured foal (Lorenzo, 2014) and one, 3,4,4-trimethyl-2-cyclopenten-1-one, 3,5,5-trimethyl-2- alcohols in San Daniele ham (Gaspardo et al., 2008). cyclopenten-1-one, 3-ethyl-2-cyclopenten-1-one), 4-methyl-4- Hydrocarbons were the most numerous of the chemical classes hepten-3-one, acetophenone, and 2,3-dihydro-1H-inden-1-one were among the volatile components detected. In general, most aromatic detected only in T1 products. In previous studies (Ansorena et al., hydrocarbons (toluene, ethylbenzene, o-xylene, p-xylene, and 2001; Hierro et al., 2004; Jónsdóttir et al., 2008; Stojković et al., styrene), and long-chain aliphatic hydrocarbons (> 10 carbon 2015), some enones such as 2-methyl-2-cyclopenten-1-one, atoms, undecane, dodecane, and tridecane) have been thought to 2,3-dimethyl-2-cyclopenten-1-one, 3,4-dimethyl-2-cyclopenten-1- originate from animal feedstuffs (Ruiz et al., 1999; Muriel et al., one, 3-methyl-2-cyclopenten-1-one, 3,5,5-trimethyl-2-cyclopenten- 2004). Numerous terpenes (α-pinen, α-phellandrene, ß-pinene, 1-one have also been reported in other smoked meat products, ß-phellandrene, 3-carene, ocimene, eucalyptol, and caryophyllene) possibly formed during the smoking process. The ketones content Characteristics of Kazakh Dry-cured Beef 379

Table 2. Volatile compounds (expressed as ng/g dry matter) detected in two types of Kazakh dry-cured beef.

Code Compound RIa T1(n=12) T2 (n=18) SEM P-level Identification Hydrocarbons A1 Hexane 806 29.61 41.78 4.17 NS MS A2 Trichloromethane 924 ND 2.66 0.77 - MS A3 ɑ-Pinene 1019 35.41 ND 8.09 - MS; RI A4 ɑ-Phellandrene 1024 10.32 ND 1.87 - MS A5 Toluene 1037 48.90 29.42 5.93 NS MS; RI A6 Undecane 1088 69.16 24.31 10.44 * MS; RI A7 ß-Pinene 1100 47.69 ND 10.71 - MS; RI A8 ß-Phellandrene 1115 17.17 ND 2.94 - MS; RI A9 Ethylbenzene 1123 29.29 11.74 4.53 NS MS; RI A10 o-Xylene 1131 22.83 15.17 2.33 NS MS; RI A11 p-Xylene 1137 32.25 30.15 6.37 NS MS; RI A12 3-Carene 1147 119 . 11 ND 30.86 - MS; RI A13 Ocimene 1176 12.05 ND 2.47 - MS A14 Dodecane 1196 134.27 49.18 21.10 * MS; RI A15 D-Limonene 1197 159.98 21.93 21.12 ** MS; RI A16 Eucalyptol 1210 205.09 ND 32.50 - MS A17 Styrene 1257 31.15 22.36 4.06 NS MS; RI A18 Tridecane 1295 92.78 40.93 18.32 NS MS; RI A19 Caryophyllene 1605 469.66 ND 146.65 - MS; RI A20 Phenylethyne 1607 ND 2.53 0.51 - MS A21 Naphthalene 1750 79.25 ND 13.95 - MS; RI Subtotal 1645.99 292.17 236.65 ** Aldehydes B1 Butanal, 3-methyl- 911 14.74 3.71 2.34 * MS; RI B2 Hexanal 1078 25.68 126.47 29.14 NS MS; RI B3 Heptanal 1183 47.77 65.84 10.84 NS MS; RI B4 Octanal 1289 39.83 77.14 19.08 NS MS; RI B5 2-Heptenal, (Z)- 1322 ND 6.11 2.62 - MS; RI B6 Nonanal 1395 157.76 253.13 54.29 NS MS; RI B7 (E)-2-Octenal 1431 3.93 13.29 3.48 NS MS; RI B8 Decanal 1496 ND 11.86 2.45 - MS; RI B9 2-Nonenal, (E)- 1536 ND 15.68 3.87 - MS; RI B10 Benzaldehyde, 4-(1-methylethyl)- 1789 18.10 ND 2.57 - MS Subtotal 307.81 573.22 120.58 NS Ketones C1 2-Pentanone 973 ND 9.95 2.17 - MS; RI C2 2-Octanone 1282 ND 9.54 2.68 - MS; RI C3 2,3-Octanedione 1319 ND 53.36 12.49 - MS; RI C4 2-Cyclopenten-1-one, 2-methyl- 1374 30.21 ND 4.24 - MS; RI C5 2-Nonanone 1387 ND 2.14 0.62 - MS; RI C6 2-Cyclopenten-1-one, 2,3-dimethyl- 1454 19.52 ND 2.65 - MS C7 2-Cyclopenten-1-one, 3,4-dimethyl- 1489 31.84 ND 4.19 - MS C8 2-Cyclopenten-1-one, 2,3,4-trimethyl- 1504 17.42 ND 2.85 - MS C9 2-Cyclopenten-1-one, 3-methyl- 1527 68.40 ND 8.80 - MS C10 2-Cyclopenten-1-one, 3,4,4-trimethyl- 1563 14.44 ND 2.14 - MS C11 2-Cyclopenten-1-one, 3,5,5-trimethyl- 1620 10.39 ND 1.46 - MS C12 2-Cyclopenten-1-one, 3-ethyl- 1639 12.53 ND 1.96 - MS C13 Acetophenone 1657 31.67 ND 3.32 - MS; RI C14 4-Hepten-3-one, 4-methyl- 1731 25.16 ND 3.37 - MS C15 1H-Inden-1-one, 2,3-dihydro- 2027 23.36 ND 2.83 - MS Subtotal 284.94 74.98 32.96 ** Alcohols 380 K. Sha et al.

Table 2. Volatile compounds (expressed as ng/g dry matter) detected in two types of Kazakh dry-cured beef.

D1 Ethanol 936 35.13 ND 4.65 - MS; RI D2 1-Penten-3-ol 1159 ND 5.88 1.58 - MS; RI D3 3-Methyl-1-butanol 1209 18.09 17.19 6.17 NS MS; RI D4 1-Pentanol 1239 2.68 16.95 3.18 * MS; RI D5 1-Hexanol 1355 16.80 68.34 18.76 NS MS; RI D6 1-Octen-3-ol 1451 21.41 83.85 15.77 NS MS; RI D7 1-Heptanol 1458 16.59 53.03 10.66 NS MS; RI D8 (E)-2-Decen-1-ol 1466 ND 2.02 0.59 - MS D9 1,6-Octadien-3-ol, 3,7-dimethyl- 1548 132.09 ND 14.72 - MS D10 1-Octanol 1560 20.13 51.94 10.36 NS MS; RI D11 3-Cyclohexen-1-ol, 4-methyl-1-(1-methylethyl)- 1608 66.87 ND 10.78 - MS D12 2-Octen-1-ol, (E)- 1615 ND 14.96 3.21 - MS D13 1-Nonanol 1659 ND 9.17 1.88 - MS; RI D14 2-Furanmethanol 1662 129.69 ND 16.03 - MS D15 Phenylethyl alcohol 1918 15.40 ND 2.37 - MS Subtotal 474.89 323.32 64.76 NS Nitrogenous E1 Pyridine, 3-methyl- 1222 20.30 ND 2.25 - MS; RI E2 Pyridine, 4-methyl- 1299 14.45 ND 1.94 - MS; RI E3 Pyridine, 2,4-dimethyl- 1333 26.18 ND 7.34 - MS; RI E4 Pyridine, 3,5-dimethyl- 1344 14.49 ND 2.15 - MS; RI E5 Oxime-, methoxy-phenyl- 1753 60.32 ND 6.50 - MS Subtotal 135.75 ND 17.39 - Furans F1 Furan, 2-pentyl- 1230 9.70 29.32 6.84 NS MS; RI F2 Furfural 1465 48.49 ND 6.21 - MS; RI F3 Ethanone, 1-(2-furanyl)- 1508 65.66 ND 7.69 - MS F4 2-Furancarboxaldehyde, 5-methyl- 1577 11.65 ND 2.43 - MS; RI Subtotal 135.51 29.32 14.96 ** Esters G1 Ethyl acetate 884 9.74 ND 1.83 - MS; RI G2 Hexanoic acid, ethyl ester 1233 9.04 ND 1.45 - MS; RI Subtotal 18.78 ND 2.51 - Ethers H1 Estragole 1675 32.84 ND 5.63 - MS; RI H2 Benzene, 1-methoxy-4-(1-propenyl)- 1832 419.40 ND 94.98 - MS Subtotal 452.24 ND 100.30 - Phenols I1 Phenol, 2-methoxy- 1863 244.17 ND 31.12 - MS; RI I2 Phenol, 4-methoxy-3-methyl- 1876 20.98 ND 2.67 - MS I3 Phenol, 2,6-dimethyl- 1912 19.61 ND 2.73 - MS I4 Phenol, 2-methoxy-4-methyl- 1961 97.45 ND 12.48 - MS; RI I5 Phenol, 2-methyl- 2005 105.39 ND 14.93 - MS I6 Phenol 2008 257.57 ND 31.20 - MS; RI I7 Phenol, 4-ethyl-2-methoxy- 2035 62.93 ND 8.14 - MS I8 Phenol, 2,5-dimethyl- 2079 22.93 ND 3.51 - MS I9 Phenol, 4-methyl- 2085 123.81 ND 15.49 - MS I10 Phenol, 3-methyl- 2093 98.79 ND 13.58 - MS I11 Phenol, 3-ethyl- 2180 25.15 ND 2.53 - MS I12 Phenol, 2,6-dimethoxy- 2272 25.89 ND 3.20 - MS Subtotal 1104.68 ND 138.81 -

RI: Retention index.a: RI in agreement with literature values for a DB-WAX capillary column.SEM: Standard error of the mean. P-level: Level of significance found by analysis of variance. NS, not significant; *, P < 0.05; **, P < 0.01.ND: Not detected. Characteristics of Kazakh Dry-cured Beef 381

Fig. 1. Score plot of principal component analysis of volatile componds from two types of Kazakh dry-cured beef. was significantly (P < 0.05) higher in the T1 products than in the processing time was relatively short, lower amounts of esters, an T2 products. aroma of typical aged-meat products, were found in Kazakh dry- Regarding alcohols, most straight-chain alcohols (1-pentanol, cured beef. 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-penten-3-ol, Two ethers (estragole and 1-methoxy-4-(1-propenyl)-benzene) 1-octen-3-ol, (E)-2-decen-1-ol, (E)-2-octen-1-ol) detected could were detected only in T1 products. They are most likely to have have been produced by lipid oxidation, while branched alcohols, come from the added spices. such as 3-methyl-1-butanol, could have arisen from the Strecker The furans detected included 2-pentyl-furan, furfural, degradation of amino acids (Pugliese et al., 2015). Other alcohols 1-(2-furanyl)-ethanone, and 5-methyl-2-furancarboxaldehyde. such as ethanol, 3,7-dimethyl-1,6-octadien-3-ol, 4-methyl-1-(1- 2-Pentyl-furan, a typical product of lipid oxidation, has been found methylethyl)-3-cyclohexen-1-ol, 2-furanmethanol, phenylethyl in other dry-cured meats (Purriños et al., 2011; Lorenzo, 2014). alcohol were detected only in T1 products. They were most likely Furfural, 1-(2-Furanyl)-ethanone, and 5-methyl-2- to have been derived from the smoking process or the use of spices furancarboxaldehyde can also be generated during the smoking in the T1 products. The alcohol content was not significantly process (Jerković, 2010). 1-(2-Furanyl)-ethanone and 5-methyl-2- (P > 0.05) different between the two types of sample. Because of furancarboxaldehyde contribute greatly to the characteristic their high sensory threshold values, most alcohols typically smoked aroma compared with furfural, a weak odorant (Jónsdóttir contribute little to the flavor of dry-cured meat products, but et al., 2008). 1-penten-3-ol and 1-octen-3-ol have been considered as important Phenols, typical flavor compounds in smoked meat products, flavor compounds (Marušićet al., 2014). have the characteristics of wood smoke derivatives from the The nitrogenous compounds detected included 3-methyl- pyrolysis of cellulose, hemicelluloses and lignin (Jerković, 2010). pyridine, 4-methyl-pyridine, 2, 4-dimethyl-pyridine, 3, 5-dimethyl- In the present study, 12 phenol derivatives were detected only in pyridine, and methoxy-phenyl-oxime. These compounds, found the T1 products. Among the phenols detected, phenol and only in T1 products, were formed by Maillard compounds or 2-methoxy-phenol, present in very high quantities, have been nitrogen-containing proteins and amino acids pyrolysis during the identified as the main compound contributing to the smokehouse smoking process (Stojković et al., 2015). 3-methyl-pyridine was odor (Jónsdóttir et al., 2008). also isolated from smoked dried meats (Hierro et al., 2004; Principal component analysis The results of the principal Stojković et al., 2015). component analysis (Fig. 1 and 2) describe the relationships Two esters (ethyl acetate and hexanoic acid ethyl ester) were between the volatile compounds detected and illustrate the detected only in T1 products. These esters are generated by differences in the volatile flavors describing the samples. The first esterification between ethanol and carboxylic acids in the presence two principal components (PC1 and PC2) explained 37.83% and of certain microorganisms (Montel et al., 1998). Since the 20.61% of the total variance, respectively, accounting for 58.44% 382 K. Sha et al.

Fig. 2. The location of samples of two types of Kazakh dry-cured beef in the first principal components (PC1 and PC2). (●, T1 products; ▲, T2 products). of the variability. Conclusions Fig. 1 shows the location of the variables in PC1 and PC2. PC1 The results of this study have provided a wider knowledge of was highly related to the volatile compounds generated during the the physicochemical and textural characteristics and volatile smoking process: naphthalene, 2-cyclopenten-1-one derivatives, compounds of Kazakh dry-cured beef. This is important for 4-methyl-4-hepten-3-one, acetophenone, 2, 3-dihydro-1H-Inden-1- controlling the quality of products and establishing product one, 2-furanmethanol, methoxy-phenyl-oxime, furfural, standards. The two types of Kazakh dry-cured beef exhibited

1-(2-furanyl)-ethanone, and phenols. The lipid-derived compounds, significant (P < 0.05) differences in the mean values of aw, straight-chain aliphatic aldehydes, methyl ketone, straight-chain moisture, L*, cohesiveness, and chewiness. A total of 86 volatile alcohols, and 2-pentyl-furan, were mainly correlated with PC2. compounds were identified and quantified by GC/MS. In Kazakh The location of the samples in PC1 and PC2 is shown in Fig. 2. dry-cured beef, hydrocarbons were the most abundant compound The two types of Kazakh dry-cured beef are clearly separated by in the T1 type and aldehydes in the T2 type. Smoke treatment, the PC1 axis. The T1 products were located on the positive axis on added spices and lipid oxidation were the main pathways for PC1, while the T2 products were located on the negative axis. generating volatile components in Kazakh dry-cured beef. Principal These results indicate marked differences in volatile flavor between component analysis showed that there were marked differences in the two types of sample. volatile flavors between the two types of samples. The main Overall, many factors are responsible for the flavor differences were caused by the presence or absence of smoke characteristics of Kazakh dry-cured beef: the added spices, derivatives and spice ingredients. smoking treatment, degree of lipid oxidation, compounds originating from animal feedstuff, the Strecker degradation of Acknowledgements This research was funded by the National amino acids and microbial metabolism. Of these factors, the added Natural Science Funds of China (Grant No.31460403). The authors spices, smoking treatment and lipid oxidation are the most acknowledge the participation of the Animal Science Academy of important pathways for generating the volatile components in Xinjiang Uygur Autonomous Region, China who collected the Kazakh dry-cured beef. The differences in the type or amount of samples. volatile components between the two types of Kazakh dry-cured beef are related to the characteristics of the raw meat, the presence References of spices, and the conditions during salting, drying, and smoking. Ansorena, D., Gimeno, O., Astiasarán, I., and Bello, J. (2001). Analysis of Therefore, further studies on the factors influencing the flavor volatile compounds by GC-MS of a dry fermented sausage: chorizo de profile of Kazakh dry-cured beef are necessary for improving the Pamplona. Food Res. Int., 34, 67-75. quality control of this product. Ceylan, S. and Aksu, M. I. (2011). Free amino acids profile and quantities Characteristics of Kazakh Dry-cured Beef 383

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