Seasonal variation in red deer (Cervus elaphus) venison (M. longissimus dorsi) drip loss, calpain activity, colour and tenderness

Sixty four young red deer (Cervus elaphus) stags (< 2 years old) were slaughtered at four different times (December (Group 1); n = 17, March (Group 2); n = 8, July (Group 3); n = 20 and September (Group 4); n = 19) to evaluate seasonal effects on venison quality. M. longissimus dorsi samples for calpain analysis were collected on the slaughter line and the rest of these muscles were collected at 1 day post-slaughter. Loins were divided into four parts and randomly allocated to storage for 1 day, 3, 9 or 14 weeks at −1.5 °C and then vacuum packaged. Seasonal variation was demonstrated in venison pH. Highly significant positive regressions were found for shear force (P < 0.001) and colour display life (P < 0.001) on pH, where higher pH values were associated with tougher venison and longer colour display life. A clear trend of increasing fluid loss during storage, calculated as amount of purge at 14 weeks of storage minus the amount of drip loss at 1 day post-slaughter, was evident, averaging 2.5% (SEM 0.17) over the four groups. The relative activities of the calpastatin-bound calpain, μ-calpain and m-calpain all exhibited a seasonal pattern although there was no evidence (P > 0.05) that this affected tenderness. There was a highly significant (P < 0.001) negative regression for the average over the four storage times of drip and purge on calpastatin-bound calpain activity.