COMPARATIVE STUDIES OF THE EFFECT OF FREEZING ON THE PHYSICOCHEMICAL PROPERTIES OF THE FILLETS OF TWO FISH SPECIES IN IRAN.

The Sparidentex hasta and Pampus argenteus species of fish consumed in the south of Iran are abundant in a particular season, so they should be frozen for consumption throughout the year. That is why this research was carried out to investigate the effects of freezing on some of the physicochemical properties of the fillets of the fishes. Such parameters were determined as fat (by the chloroform-methanol method), the amount of TBA (thiobarbituric acid) in fish muscle (by Pearson's method), pH (with a pH meter), and FFA (Free fatty acids) - by the titration method, in the presence of phenolphthalein. They were determined basing on the percentage of oleic acid. The peroxide value, according to AOAC (Association of Official Analytical Chemists), was tested in fresh samples at time zero and after different periods of freezing. The results showed that the TBA content in fish fillet for Pampus argenteus and Sparidentex hasta was 0.65 and 0.53, respectively. The highest percentage of fat was found for Pampus argenteus after 95 days (24.22%), and for Sparidentex hasta after 35 days (25.19%). The highest free fatty acids contents (0.9% and 0.97%) was found for Sparidentex hasta and Pampus argenteus after 95 days. It can be concluded that the TBA and FFA contents and pH of both fish species increased during storage in a freezer. The peroxide value in Pampus argenteus was reduced, but in Sparidentex hasta showed no significant differentce. The best time of storage of Pampus argenteus and Sparidentex hasta at -18°C was 35 days of freezing, but the nutritional value of the fillets and the fatty acids reduced greatly. [ABSTRACT FROM AUTHOR]