Abstract:The aim of this paper was to investigate the changes of protein, lipid oxidation and its impact on water holding capacity of Psoas major, Quadriceps femoris and Longissimus dorsi from yak during 140d of frozen storage (-18℃). Samples were analyzed at sampling times upon thawing (0, 28, 56, 84 and 140d) for lipid (TBARS, hexanal) and protein oxidation products (α-aminoadipic and γ-glutamic semialdehydes, α-aminoadipic acid, Schiff bases). During the frozen storage, heme-iron and superoxide dismutase played an important role in the lipid oxidation process of Longissimus dorsi. Owing to a lower content of heme-iron and a relatively higher content of superoxide dismutase, Longissimus dorsi had a lower content of TBARS and hexanal. Frozen storage significantly influenced the oxidative stability of proteins in Psoas major and Quadriceps femoris. The protein oxidation process of PM and QF was co-regulated by heme-iron, superoxide dismutase and catalase. Because of the promoting oxidation of heme-iron, the content of α-aminoadipic and γ-glutamic semialdehydes were also significantly improved. However, the content of heme-iron in Psoas major was significantly higher than Quadriceps femoris, the content of α-aminoadipic and γ-glutamic semialdehydes in Psoas major and Quadriceps femoris had no significant differences due to the higher content of superoxide dismutase and catalase. The content of α-aminoadipic acid was relatively higher because of the higher content of heme-iron in Psoas major, but the content of α-aminoadipic acid in Psoas major was significantly lower than Quadriceps femoris (P<0.05). Furthermore, the water holding capacity of yak meat was significantly affected by protein carbonylation reaction during the frozen storage. Owing to the lowest antioxidant enzyme activity and the highest heme-iron, the water holding capacity of Quadriceps femoris was the worst in three kinds of yak meat. The purge of Quadriceps femoris was higher than Longissimus dorsi for 3.55 times.
