Changes in Toughness, Leaching Loss and Myofibril Fragmentation of Pacific Saury (Cololabis saira) Muscle during Iced Storage

Abstract

The effect of myofibril fragmentation on the changes in toughness and leaching loss of Pacific saury (Cololabis saira) muscle was studied. Frozen round fish was thawed and provided to the experiment of 10-days ice-storage. The toughness of fillet decreased during the initial 5-days storage and it maintained the constant thereafter. As the ordinary muscle of fish was minced and washed conventionally with alkali medium to lighten the color, the dry mass lost was 77% when fish were stored for 5 days. It would increase to 93% as prolonging storage of samples to 7 days. Myofibrils fragmentized quickly during the iced storage. According to the numbers of sarcomere in one fragment, the myofibril fragmentations were classified to three groups: 1-4 sarcomeres (group A), 5-10 sarcomeres (group B), and above 10 sarcomeres (group C). The proportion of numbers of A group to the sum of 3 groups (fragmentation ratio) extracted from 5-days iced fish was 81%, and it became 92% from those of 7-days storage fish. The changes in the means of numbers of Group A+C or Group B+C showed high correlation with the changes in leaching loss and toughness of flesh respectively (r^2 0.950, 0.852,). SDS-polyacrylamide gel electrophoresis patterns showed no obvious changes in water-soluble sarcoplasmic and salt-soluble myofibrillar proteins. Though alkali-soluble protein showed similar patterns during the storage, the bands showed the increasing intensity with the prolonging storage period. It suggested that the high leaching loss of Pacific saury minced muscle during the iced storage was mainly resulted from the fragmentation of myofibril but not the denaturation of protein.