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Rutilus frisii kutum is one of the most important and economic fish in our country. Since the passage of time and temperature on the quality of fish caught continuous reduced, so decreasing the temperature by ice storage, immediately after fishing, is a good methodto avoid loss of quality fall. Inthisstudy change of some quality parameters of R. frisii kutum during ice storage for 16 days such as expressible moisture, pH, thiobarbituric acid, total volatile nitrogen, free fatty acid, psychrotrophic count and total viable count to assessment the effects of delay of putting ice on fish caught and loss in quality product was measured. According to these results, the chemical and bacterial indicators were increased significantly during the storage in ice. Delayed icing caused the higher degree of oxidation. Furthermore, delayed icing, lack of attention to correct method of storage, and ice storage for a long time can decrease the quality of meat. It is better that fish be ice storage after fishing immediately. Shorten the shelf life of the product on the ice and accelerate cooling, helps to increase the shelf life of the product.  

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The purpose of this study was to investigate the effect of different methods of preparation of raw rainbow trout (Oncorhynchus mykis) (full, empty stomach, fillets and fillets of butterflies) on quality and shelf life was over 4 months of storage in home freezers. To this end, rainbow trout  transferred to the laboratory and washed, were prepared by the method described and qualitative assessment of fish at the end of each month by measurement of chemical parameters (free fatty acids, thiobarbituric acid, protein, fat, moisture, ash, under pressure moisture, pH, heme iron content) and sensory (flavour, odor, texture, color) were performed. With increasing storage time heme iron content reduced, so that at the end of storage heme iron content was more in treatment of whole fish. Also under pressure moisture, TBA nad FFA increased in different treatments and in the fourth month of storage, the rate of these variables were lower in treatments of whole fish. Sensory analysis results indicate utility of all treatments decreased with increasing storage time but the rate of decline was less than in whole fish. According to the results, as can be fish kept in perfect shape than in other forms it is recommended.

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Skin, bones, frames, heads and tails are by-products produced during the processing of fish and prawn. These by-products can be enzymatically hydrolyzed and be converted products with beneficial functional properties. So, Protein hydrolysates were prepared from green tiger prawn (Penaeus semisulcatus) waste using flavourzyme and response surface methodology (RSM) based on 18 treatments was applied to study the effect of enzyme to substrate ratio, temperature and time on the protein. The antioxidant activities were measured using 2,2-diphenyl-1-picryl-hydrazyl (DPPH), hydroxyl radical-scavenging activity and ferric reducing antioxidant power. Totally, products have showen better response in 2,2-diphenyl-1-picryl-hydrazyl (DPPH) scavenging activity in comparison to hydroxyl radical-scavenging activity and Ferric (Fe³⁺) reducing antioxidant activity.. Among the treatments produced, 7 treatment (hydrolysis temperature of 54.6 ⁰C together with enzyme to substrate ratio of 1.61 % and hydrolysis time of 105.8 min) with degree of hydrolysis (33.5%) and protein (79.5%) were the optimum conditions to obtain the highest antioxidant properties. These results suggested that prawn waste protein hydrolysates could be useful in the food industry.