Search

The present study investigated the effect of slaughter age (2.43 ± 0.20, 4.15 ± 0.19, 6.62 ± 0.18, 10.59 ± 0.74 years) and postmortem aging time (1, 24, and 72 h) on the tenderness and water-holding capacity (WHC) of yak longissimus thoracis muscles to determine the most suitable age for slaughter to ensure product consistency. Under conventional postmortem aging conditions (4 °C), muscles of each age group exhibited the effect of cold shortening. Once the cold shortening occurred, the age effect on thickening muscle fiber and developing cross-links of collagen, considered to intensify the meat toughness, became less important. Owing to greater carcass weight and intramuscular fat, muscles of the older carcass (over 6-year-old) were less influenced by the cold shortening effect during the chilling process and showed lessened sarcomere contraction, delayed formation of drip loss channels, and increased level of myofibril fragmentation index (MFI) and myofiber structural disintegration, resulting in greater tenderness and WHC, especially 6–7 years group. Aging of 72 h structurally disintegrated the collagen cross-linking and integrity of muscle fibers and elevated the MFI, improving the meat tenderness. Therefore, the suitable slaughter age for yak is 6–7 years old and after 72 h aging, improved quality of yak meat can be obtained. • Beef tenderness and WHC elevated as yak aged under postmortem aging at 4 °C. • Yaks of 6–7 years are suitable to slaughter under conventional aging condition. • Cold shortening dominated quality variations of aged (at 4 °C) yak beef across ages. • Age-related differences in cold shortening appeared after 1 h postmortem. • Collagen cross-links increased as animals grew while reduced during postmortem aging. [ABSTRACT FROM AUTHOR]

• ST, LT and IS have specific myofiber type compositions that affect redox properties. • IS is prone to higher-level oxidation, especially protein oxidation. • Type Ⅰ myofiber positively correlated with T -Mb content and antioxidase activities. • Type Ⅰ myofiber has a positive relation with IMF and SFA and a negative one with MUFA. Yak infraspinatus (IS), longissimus thoracis (LT), and semitendinosus (ST) muscles were used to explore relationships between myofiber types and postmortem redox characteristics. IS mainly consisted of myofiber type Ⅰ (49.2%), LT has a vast majority of type IIa (72.7%), while ST possessed a similar percentage of type IIa (44.7%) and IIb (51.5%). Compared with LT and ST, IS exhibited higher initial H 2 O 2 , myoglobin (T-Mb), and metmyoglobin (MetMb) contents that provoked severe protein oxidation despite higher endogenous antioxidative capacity (e.g., glutathione antioxidative system). Three muscles showed specificities in myofiber type composition and redox characteristics, which were strongly correlated. Specifically, type Ⅰ myofiber positively correlated with H 2 O 2 , T-Mb, and multiple antioxidase activity/content while negatively correlated with lipid peroxidation, MetMb, and lactic dehydrogenase activity; also, they tended to employ more SFAs in more intermuscular fat assembly. Overall, muscle-specific myofiber type/redox attributes required differentiated processing to prevent meat oxidation and produce standardized products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Age-related redox states during the postmortem period were investigated. • Muscles of older yak were prone to postmortem oxidation of lipid and protein. • Extending postmortem time elevated meat oxidation and reduced antioxidative capacity. • The formation of age-specific oxidative properties correlated to its antioxidant ones. • Older yak reserved more intramuscular fat with less polyunsaturated fatty acids. Effects of age on postmortem redox states were investigated in yak muscles. Extended postmortem time reduced the muscle antioxidant capacity and induced oxidation in lipids, myoglobin, and proteins. Compared with older yaks, muscles of younger ones could delay this oxidation process due to lower initial myoglobin content of 30.7%, lipid peroxidation of 42.4%, H 2 O 2 of 41.2%, and intramuscular fat of 65.6% (of 3.66 times higher PUFAs). They also possessed greater antioxidase content/activity, such as phospholipase A2 content of 30.7% and glutathione reductase activity of 50.6%. Muscles exhibited age-specific overall antioxidative characteristics during 72 h postmortem and gradually formed overall oxidative ones after 72 h postmortem with an initial similarity between 2- and 4-year (or 6- and 12-year) on canonical discriminant analyses. The formation of age-specific overall oxidative characteristics can be attributable to the antioxidative specificity of age on canonical correlation analyses. Age-specific redox characteristics required differentiated preference in meat processing and preservation. [ABSTRACT FROM AUTHOR]