Sea foods are considered as an invaluable source of nutrients with positive effects on human health and nutrition. The importance of sea foods and fish is in providing protein, fat specially unsaturated fat of w3 fatty acids, some minerals and vitamins. Increasing demand for consumption of fish and its products and the shortage of fish has led to farm fish. Rainbow trout ( Oncorhynchus mykiss ) and Grass carp ( Ctenopharyngodon idella ) are two of the more appreciated freshwater species farmed vastly in Isfahan to meet the increasing demand of consumers. Despite having numerous lakes, rivers and artificial facilities for farming fish in Iran , some people suffer malnutrition and its consequences. One of the reasons is that fish is a very perishable food and there is not suitable access to correct methods for capture, storage and process of fish. In part one of this project, proximate analysis was done for rainbow trout as a coldwater fish and grass carp as a warm water fish. In second part effect of gutting on some chemical properties such as pH, TBA, TVB-N, histamine content, proteolytic activity, tyrosine value and texture in both fish during 24 hour iced storage (0, 12, 24 hours) and frozen storage (1, 3, 5 months) was investigated. Protein, moisture and especially fat content were different in fish samples but there was no significant difference in their ash values. Results showed that gutting has no significant effect on most studied factors during iced and frozen storage. Gutting treatment had however effects on histamine content and TVB-N during the same period. TBA and tyrosine values were also increased. Histamine content and TVB-N increased during ice storage but not during frozen storage. Penetration force got decreased significantly during iced storage and slightly increased during frozen storage. pH did not change during iced storage, whereas during frozen storage, undergone some changes and finally proteolytic activity didn't change during this period. Both fish were similar in some factors (TBA, pH, TVB-N and Proteolytic activity) but were significantly different in tyrosine values, Texture and histamine content. Finally, at the end of 5 months storage, and due to the storage conditions employed in this study, both fish were recognized suitable for human use.
