Effect of frozen storage on protein denaturation in bovine muscle 1. Myofibrillar ATPase activity and differential scanning calorimetric studies

The effect of frozen storage on myofibrillar ATPase activity and thermal transitions in bovine muscle was investigated. Myofibrillar ATPase activity and total enthalpy of denaturation (ΔH) decreased with time of storage. The rate of decrease was lower at −20°C than at −5°C or −10°C. Differences in behaviour during storage of muscle after fast or slow freezing could be attributed to differences in ice recrystallization. The observed decreases in area of the first peak seen in the thermograms and Ca2+‐myo‐fibrillar ATPase activity show that the myosin head denaturated progressively during storage. The myosin tail also denaturated during storage but the thin filament remained unaltered. Kinetic analysis suggested that the denaturation of the myofibrillar proteins took place through two consecutive first order reactions; an initial rapid reaction followed by a slower one.