OXIDATIVE ALTERATIONS OF LIPIDS IN FROZEN FISH AT DIFFERENT TIME AND SPEED DURING FROZEN STORAGE

The aim of this study was to determine the effects of temperature and time of freezing on lipid oxidation in anchovy during frozen storage.

Fresh anchovy (Engraulis encrasicholus) was used as material. The fish were frozen at three different temperatures (-20°C, -40°C and -80°C). During the freezing, temperature of thermal centre of fish was measured using a thermo couple and then time of freezing was calculated. Frozen fish were stored in a deep freezer at -18°C for 6 months. Analyses were conducted at monthly intervals. Freezing time and freezing velocity were calculated. Peroxide, tiobarbutiric acid (TBA),   Para-anisidine (p-Av),  free fatty acids (FFA) and conjugated diene (CD) values were determined during the storage.

The highest freezing speed and the shortest freezing time were observed for anchovies frozen at -80°C. Peroxide (PV), thiobarbutiric acid (TBA), para-anisidine (p-Av), conjugated diene (CD) and free fatty acid (FFA) values were significantly affected by freezing temperature. Low freezing temperature resulted in low oxidation level. Oxidation levels significantly increased during the storage. The lowest values were determined in the samples frozen at -80°C. The best freezing temperature in terms of delaying of lipid oxidation was found to be -80°C.