Effect of Frozen Storage Periods on Quality Indices of some Processed Fishery Products. تأثیر التخزین بالتجمید وطرق الطهى المختلفة على دلائل الجودة فى الاسماک

Abstract

This study was designed to investigate the effect of frozen storage periods at-18oC for 6 month on some physico-chemical quality indices of processed fishery products. Two fish species; Tilapia (Oreochromis niloticus) as freshwater fish and big eyed snapper (Latjenus spp.) as marine fish were purchased from Benha fish market. Raw whole fish samples were carefully washed, glazed, packed in foam dishes covered with polyethylene sheet and stored under freezing conditions. Frying, grilling, microwave cooking and boiling techniques were applied. Results showed that all quality indices were affected by storage periods as well as cooking techniques applied. pH values recorded a high decrease at the end of storage; 90 and 180 days for big eyed snapper and tilapia samples, respectively. Values of total volatile basic nitrogen (TVB), trimethylamine (TMA), and thiobarbituric acid (TBA) were increased with prolonging storage periods and fluctuated. Concerning effect of cooking techniques, it was found that pH values decreased in cooked tilapia products and increased in cooked snapper products. However, values of TVB, TMA and TBA were increased in all studied products. In conclusion, based on our results, it could be concluded that snapper fish samples were lower in freshness grade than tilapia samples. Freezing process has been affected chemically quality indices especially at the end of storage. Fluctuation in quality indices are due to fish spp., freshness degree, handling processes and frozen storage periods. Besides, different cooking techniques are affected quality indices investigated according to thermal conditions used.