IMPORTANCE OF FROZEN STORAGE-TEMPERATURE IN THE TYPE OF AGGREGATION OF MYOFIBRILLAR PROTEINS IN COD (GADUS-MORHUA) FILLETS

Cod fillets were examined to determine the effect of two frozen storag e temperatures (-20 and -30 degrees C) on the formation of aggregates and if this relates to changes in texture and functionality. The evolu tion of apparent viscosity during frozen storage was similar at either storage temperature. Loss of extractability in 0.6 M NaCl was slightl y greater at -20 degrees C. The aggregate which formed at -30 degrees C was extractable in solutions which cleave secondary interactions [2% sodium dodecyl sulfate (SDS)] whereas at -20 degrees C the role of no n-disulfide covalent bonds was more important, so that this aggregate was not totally extracted in 2% SDS plus 5% beta-mercaptoethanol. The aggregates consisted largely of myosin and actin, but myosin was the m ost important constituent, contributing more to the formation of coval ent bonds, particularly at the higher temperature. This difference in aggregation was accompanied with a difference in the evolution over ti me of shear resistance, which was higher at -20 degrees C.