The Qualities Change Of Different Meat Cuts Of Yak During Fermentation And The Evaluation Of Finished Products Qualities

In this study, different meat cuts(semitendinosus SEM, biceps femoris BF, rectus femorisRF, vastus medialis VM, vastus lateralis VL) of yak which divided into three groups (2-4,4-6,>6) by slaughter age as objects.Studyed on regularity of qualities（physicochemical,texture and flavor）establishment and texture properties, odor-active compounds, fatty acidcomposition, amino acid composition and there contributions to taste of products duringfermentation in existed process. The senseory qualities of products had been also evaluated byfuzzy comprehensive mathematical method. In oder to provide a theoretical basis forindustrial production of fermented yak meat.The results as follows:1During the fermentation, appearance characteristics were changed obviously. L*values(Lightness) were decreased (P<0.05). Fluctuated increasing tend of a*values (Redness) wasobserved (P<0.05). Meanwhile, b*values (yellowness) were decreased (P<0.05). Weight lossratio and water loss ratio was increased gradually for all samples (P<0.05). Weight loss ratioand water loss ratio of4-6VM reached the highest level (33.20%and32.35%, respectively)at15d. A significantly decreased tend was observed in moisture contents (P<0.05). The loss ofmoisture of4-6VL and2-4SEM were significantly higher than others during0-5days.Thecontents of protein and fat were increased significantly (P<0.05).2. Stepwise linear regression analysis was used to establish the regression linear modelsbetween Aw (X1), pH value (X2), protein content (X3), fat content (X4), moisture content (X5),salt concentration (Y1), weight loss ratio (Y2), absolute moisture content (Y3), total nitrogencontent (Y4), non-protein nitrogen content (Y5), results were presented as follows:Y1=29.723-0.126X5-30.986X1+2.024X2, R2=0.902;Y2=88.568-1.203X5, R2=0.925;Y3=-3.976+0.064X5+0.739X2-2.468X1, R2=0.982;Y4=22.134-8.766X1, R2=0.110;Y5=25.556-3.992X2, R2=0.387.The results showed that the linear regression models of salt concentration, weight lossratio, and absolute moisture concent had a good prediction function.3. During the fermentation, Hardness of all samples was increased significantly (P<0.05).A trend of rise first then fall was observed in springiness and adhesiveness (P<0.05), in which,there were not different in springiness during the duration of fermentation (P>0.05). However,adhesiveness showed significant decrease (P<0.05). Used the textural properties data ofdifferent fermented Yak meat as criterion of association, it was possible to distinguish threediferent clusters. The first category contains the4-6age group BF, SEM, RF, VM, 2-4BF,>6SEM, which is characterized by higher chewiness, lower hardness, adhesivenessand cohesiveness. The second category contains4-6VL,2-4SEM, characterized by lowerhardness, higher adhesiveness, cohesiveness and springiness. The third category is>6BFwhich is characterized by highest hardness, chewiness, higher cohesiveness, lowestadhesiveness.4. Difference in sensory qualities was found among different fermented yak meat. Thefermented Yak meat processed by SEM was better than that of BF. For the SEM basedproducts, the composite score of three age groups (2-4,4-6,>6) were different. Specifically,group that over6years old showed the highest composite score, and then was4-6years oldgroup,2-4years old group, respectively.5. Cineol, linalool, phenylethyl alcohol, benzaldehyde,2-nonanone,3-hydroxy-2-butanone, dimethyl disulfide,2-acetyl-1-pyrroline were key odor compounds of fermentedyak meat. On the whole, fermented Yak meat showed mint fragrance, sweet, meaty andfragrant popcorn. Meanwhile,3-carene, ethylbenzene,2-methylnaphthalene andnonylaldehyde were likely to the overall flavor also has an important contribution.6． Fermented yak meat, riched in glutamate content, and lysine content higher than thedesired level. However, methionine was the first limiting amino acid for fermented yakmeat.The largest contribution to the taste of the fermented was glutamate, followed byhistidine, lysine, valine, arginine, alanine, respectively.The TAV value of threonine, which inproducts made by BF, SEM (2-4years group) was0.9,0.9, respectively. It had lower tastecontribution to overall taste than others.7． Linoleic content was higher level in functional fatty acid composition of fermented.The content of unsaturated fatty acid was significantly higher than saturated fatty acids s infermented Yak meat.