CALPAINS FROM THAW RIGOR MUSCLE

Pre-rigor beef M. Longissimus lumborum and diaphragma were frozen at - 70 degrees C and thawed at different temperatures and the activities o f extracted calpains and the toughness of heated meat compared with th ose in chilled muscle. Fresh muscle contained about 14 mu g of mu-calp ain/g and was unaffected by freezing, bur was reduced after thawing. R apid thawing at 30 degrees C for 20 min reduced the mu-calpain to 14%. When cooked from the frozen state, extensive shortening occurred and tender meat was obtained. By storing at -3 degrees C for 1 day, thaw-s hortening was prevented, but tougher meat obtained. The mu-calpain dec reased to 70% whilst the m-calpain was unaffected. Toughness decreased after further storage at -3 degrees C, as did the mu-calpain. The lat ter changes were similar to those during development of rigor mortis a nd ageing of non-shortened meat stored at 4 degrees C. Variation in ca lpain activity, rather than in sarcomere length, are likely to be the cause of toughness variation in thaw rigor muscle. Copyright (C) 1996 Elsevier Science Ltd