Ultrastructural changes during frozen storage of cod (Gadus morhua L.)

Summary Myofibrils and solutions of myofibrillar protein from post‐rigor cod muscle were studied with electron microscopy after incubation with linoleic acid and linoleic acid hydroperoxides. Linoleic acid hydroperoxides were ten times more effective than linoleic acid in reducing the amount of protein in KCl‐extracts from incubated myofibrils. Small quantities of hydroperoxides caused precipitation of isolated myofibrillar proteins. Differences in the structure and aggregation pattern of extracted proteins suggest that linoleic acid and hydroperoxides exert their effects by different mechanisms. According to the structure of extracted myofibrils, linoleic acid seemed to prevent the dissolution of the myofibril framework but appeared not to impair the extraction of myosin. Hydroperoxides appeared to cause a retention of A‐bands (myosin) in the myofibrils and in this respect showed similarities to the effect of frozen storage previously observed.