Abstract:

The objectives of this study were to investigate the myofibrillar protein oxidation of longissimus dorsi and biceps
femoris in ordinary or vacuum packaging under the frozen storage conditions. Myofibrillar protein extraction, myofibrillar
protein K-ATPase activity, Ca2+-ATPase activity, total sulfhydryl content, protein solubility, protein carbonyl content and
surface hydrophobicity were measured, and the changes of protein electrophoresis were analyzed. The results showed that
the carbonyl content significantly increased at 60 days of storage (P < 0.05), but decreased in all other treatment groups at 90
days except for a significant increase observed for biceps femoris under ordinary packaging (P > 0.05). The total sulfhydryl
content significantly increased in general during the storage period for 60 days (P < 0.05) but displayed a decreasing trend
on the 60th onward. For both muscles, hydrophobic surface with ordinary packaging was higher than that with vacuum
packaging when the storage period exceeded 90 days. Myofibrillar protein Ca2+-ATPase activty of longissimus dorsi was
higher than that of biceps femoris, yet no significant difference in K-ATPase activity was observed. Myofibrillar protein
solubility of longissimus dorsi changed significantly (P < 0.05), while the changes in myofibrillar protein solubility of
biceps femoris were not statistically significant (P > 0.05). Additionally, we found that protein bands changed during frozen
storage. Myosin heavy chain and actin were degraded to varying degrees with prolonging the frozen storage time. This study
indicates that with prolonged frozen storage time, oxidation occurs on myofibrillar protein of yak meat, which provides a
strong basis for further clarifying the mechanism of muscle protein oxidation.

Key words: yak meat, myofibrillar protein, oxidation, physicochemical properties