Effects of Slaughter Age on the Quality of Gannan Yak Meat: Analysis of Edible Quality, Nutritional Value, and GC × GC-ToF-MS of the Longissimus Dorsi Muscle

Gannan yak meat is a natural green organic food with rich nutritional value. However, the slaughter age of Gannan yak in the market is older and has lower meat quality. In this study, yaks of different slaughtering ages were selected to assess the edible quality, nutritional value, and flavor characteristics of the longissimus dorsi (LD) muscle, and the optimal slaughtering age was identified based on the results. The results showed that the shear force (6.10 kgf), water loss rate (26.89%), cooking loss (23.71%), and drip loss (1.95%) of yak meat were significantly lower when the slaughter age was 2–4 years than in the other slaughter age groups (p < 0.05). Meanwhile, the cohesiveness (0.73%), elasticity (0.86), gumminess (61.71 mJ), monounsaturated fatty acid (0.4591 g/100 g), and polyunsaturated fatty acid contents (0.1232 g/100 g) of yak meat were significantly higher in the 2–4-year slaughter age group (p < 0.05). Additionally, through GC × GC-ToF-MS analysis, a slaughter age of 2–4 years yielded yak meat with the highest content of key active flavor substances (e.g., 2-nonenal, (E)-, 2,3-butanedione, etc.) and corresponding relative odor activity values (p < 0.05), making it more complex and conferring distinct flavor characteristics. In summary, meat obtained from 2 to 4-year-old Gannan yak was superior in terms of edible quality, nutritional value, and flavor characteristics and was more suitable for processing into high-quality meat products.