Effects of frosting procedure in different temperatures and periods on oil oxidation of anchovy

In this study effects of frosting in different temperatures and periods on oil oxidation during storage of anchovy are explored in order to determine the most proper frosting temperature in terms of fish quality.Anchovies, freshly supplied from Antalya fish market, were delivered to laboratory in the iced cases in the shortest time; the fresh fishes were analyzed in the laboratory before frosting procedure. Fishes were split into 3 different groups. The first group was frosted in -20 0C, the second group in -40 0C, and the third group in -80 0C. Freezing time and freezing speed were calculated by measuring thermal center temperature via thermocouple during frosting. Frozen fishes were stored in -18 0C for 6 months. During storage fishes were taken from storeroom once a month and after thawing oxidation level in fish oil was determined. Analyses were executed in two parallels and trials were performed two times.The highest freezing speed was achieved in frosting procedure in -80 0C as 3.12 cm/h; and therefore the shortest freezing time was seen in the anchovies frosted in -80°C as 0.48 hour. Peroxide value showed important increase (p<0.01) during storage. The lowest peroxide values were determined in the anchovies frosted in -80 °C. TBA values showed important increase (p<0.01) during storage. In the end of storage period TBA values were determined as 13.32±1.15, 12.88±0.71, 9.04±0.41 mgMDA/kg respectively in the samples frosted in -20°C, -40°C ve -80°C. The most successful result in preventing oxidation in the findings regarding para-anisidine value was determined in anchovy samples frosted in -80 0C in the end of 6 month storage period and it got the value 14.92±0.02. Conjugated diene values significantly increased (p<0.01) during storage. The lowest values were seen in the anchovies frosted in -80 °C. There were no difference found statistically in the samples frosted in -20°C and -40°C in terms of free fatty acidity values. The lowest free fatty acidity values were observed in the anchovies frosted in -40°C.As a result of the study it was determined that the most proper frosting temperature is -80 0C in order to prevent oxidation in terms of fish quality. In applications of different frosting temperatures it is seen that anchovy can be stored for 5 months without losing its edibleness.KEY WORDS: Frosting, storage by frosting, freezing time, freezing speed, frosting method, anchovy