Suppression effect of ATP on freeze denaturation of fish myofibrillar protein

Fish which are frozen pre-rigor have a better quality on thawing than fish of lower initial freshness. On the other hand, there have been few scientific reports on why muscle protein of fresh fish is more stable during frozen storage than that of less fresh ones. In this study, we focused on the function of ATP in pre-rigor muscle with a high content of ATP on the freeze tolerance of muscle protein. For this study, we developed a medium system of myofibrillar protein to maintain a high ATP concentration as a model of high ATP content muscle. Myofibrillar protein solutions made from Alaska pollack Theragra chalcogramma or croaker Argyrosomus argentatus surimi were frozen at -15, -20, -30 and - 78 degrees C for several months with various concentrations of ATP. The extractability of actomyosin from the thawed myofibrillar protein and its ATPase activity were measured. Freeze denaturation of myofibrillar protein was suppressed by the addition of ATP. The suppression effect of ATP on freeze denaturation depended on the ATP concentration, freezing temperature and fish species. This suggested that the ATP remaining in pre-rigor fish muscle works as a cryoprotectant during frozen storage.