Change of K-value and water state of yellowfin tuna Thunnus albacares meatstored in a wide temperature range (20 degrees C to -84 degrees C)

The study on K value change at low temperature storage had been carried out down to a temperature of -40 degreesC, however, there was no evidence abou t this reaction rate if the temperature were lowered below the storage temp erature normally used especially for tuna meat (-60 degreesC). The rate of K value change (k(f)) of yellowfin tuna (Thunnus albacares) meat was determ ined during storage at a wide temperature range (20 degreesC to -84 degrees C). The logarithm of K'(= 100 - K value) was used in this study and its plo t against storage time yielded a straight line, which indicated an apparent first-order reaction for all temperature storage. Furthermore, physicochem ical characterization of water in tuna muscle was carried out using Differe ntial Scanning Calorimetry (DSC) at very low temperature. The temperature d ependence of this reaction was analyzed by an Arrhenius's plot that resulte d in two break points. The first break point occurring at freezing point mi ght be due to the freeze effect. The second break point was at -10 degreesC . The reaction rate change steeply declined at the temperature range of -70 degreesC to -84 degreesC, and was thought to be related to glass transitio n which may occur in the fish sample.