Changes of Physicochemical Properties and Volatile Flavor Substances in Tibetan Air-dried Yak Meat Jerky during the Simulated Processing

The changes of water activity(Aw),pH,color,thiobarbituric acid value(TBA value),and volatile flavor substances of yak longissimus dorsi during simulated Tibetan air-dried yak meat jerky processing were studied under the conditions of freezing -20 ℃ for 6 h,and then 40 ℃ air-dried 20 h,air-dried at 60 ℃ for 10 h,or air-dried 80 ℃ for 5 h. The results showed that as the air-dried temperature increasing,the rate of descent in Aw increased. The pH was increased first and then decreased,and the rising rate was 60 ℃ > 40 ℃ > 80 ℃. The L^* value decreased first and then increased after three times of freeze-drying cycles,the rising rate was 60 ℃ > 80 ℃ > 40 ℃. The a^* value and b^* value significantly decreased(P<0.05),and the rate of decline was 40 ℃ > 80 ℃ > 60 ℃. The TBA values were significantly increased(P<0.05),the increasing rate was 60 ℃ > 40 ℃ > 80 ℃. Seven kinds of volatile flavor compounds were detected in Tibetan air-dried yak meat jerky. Three principal components were obtained by principal component analysis,and the cumulative contribution rate reached 76.117%. PC1 was 38.565% and consists of acids,aldehydes,alcohols,olefins and sulfur compounds. PC2 was 22.198% and consists of acids and ketones. PC3 was 15.354% and consists of heterocycles. The scores of volatile flavor substances on PC1,PC2,and PC3 at different air-dried time points were different. The highest scores was obtained on PC1 and PC2 when air-dried at 40 ℃ to 12 h.The highest scores on PC1 at 60 ℃ after air-dried to 8 h. The highest scores in PC1 at 80 ℃ after air-dried for 3 h. Comparing Tibetan freeze-drying at different air-drying temperatures had different effects on the physical and chemical properties of yak and changes in volatile flavor substances.