Phospholipid hydrolysis in cod flesh stored at various temperatures

Abstract

AbstractCod were stored at 20, 0, −14, −22 and −29°, samples being withdrawn at intervals, the lipids extracted and analysed for free fatty acids (FFA) and phosphorus. Chloroform or toluene vapour ultimately inhibited enzymic liberation of FFA, hence studies at o and 20° were with small pieces of flesh obtained aseptically and stored without preservative. Tests with cooked fish showed that non‐enzymic hydrolysis is negligible. Comparison of sterile fish at 0° with non‐sterile iced fish showed that all phospholipid breakdown in iced cod can be attributed to autolysis. At 0°, but not at the other temperatures, there is a marked initial lag before rapid hydrolysis begins. Only rough comparison is possible from the data available, but the rate of hydrolysis at −14° is about 10 times that at −22°. At 0° hydrolysis proceeds little faster than at −14°, while the rate at 20° is about 3 times that at 0°. Data at −29° are too few even for rough comparison. At all temperatures studied the only products accumulating from phospholipid degradation are FFA and water‐soluble phosphorus derivatives. The similar course of phospholipid hydrolysis and of protein denaturation in frozen cod was confirmed and its possible significance is discussed.