The impact of storage during on nutrients composition and organoleptic properties of fish Siganus javus in ice cover in Behbahan

Keeping fish in crushed ice will preserve the nutritional quality of the food and its ingredients. Keeping fish in crushed ice will preserve the nutritional quality and its ingredients. Enzymes and microorganisms immediately begin to fish spoilage and cause the production of compounds that lead to the destruction of fish and its unconsumption. The keeping fish in ice in the market until consumption without fish being frozen is good method for its preservation. Even if the fish are frozen immediately after the catch, it is necessary that with the precision and the speed required, it kept under cool conditions in the refrigerator, it is still not possible to ensure that the product remain its qualitative characteristics for a suitable period of time. Although the activity of the bacteria stops at temperatures of -10 ° C, but during the storage of fish in the freezer, chemical reactions (enzymatic and non-enzymatic) even slowly continue at temperatures of -30 ° C. They will cause organoleptic properties changes and weight loss and fish fat changes. These processes lead to unwanted changes during storage and thus reduce product quality. The aim of this study was to study on effect of fish Siganus javus storage time in ice powder on proximate composition and organoleptic properties. The number 8 health and live fishes of Siganus javus randomly were elected from Dylam Bander, with same size and an average weight of 200±3500 g. Fishes for 20 days were placed in polystyrene boxes in layers of powdered ice with ratio 1 to 1 and with thickness of approximately 5 cm. The sampling was carried after 1, 4, 7, 10, 13 and 20 days. The after removing wastes, samples were washed with water and then fish fillets were transferred to Ahvaz veterinary laboratory for analysis of chemical compounds. The method (AOAC, 2005) was used for analysis of proximate composition and peroxide index. The sensory evaluation parameters were determined by five test panelists based on Lane and Morris method. The results showed proximate composition was changed under of ice cover. The results showed that samples in tenth day, found with highest protein content. Different time periods in ice cover significantly were affected on fish sensory evaluation, so that the quality of fish was decreased with time. The results of crude protein measurements showed a decreasing and increasing in fish fillets studied during the maintenance period. The statistical test showed that there was a significant increase between the mean values of crude protein on the first day (zero) and the last day of storage (twentieth) (P<0.05). The amount of protein in the first day of storage was 65.68%, which increased significantly to the tenth day to 74.57%, then the factor was decreasing and on the twentieth day it reached 40.52%. This change was also statistically significant (P <0.5). Reducing the amount of proteins during storage can be attributed to the production of broken polypeptide chains and the denaturation of proteins and the conversion of nitrogen to volatile compounds, and these processes were carried out in inappropriate temperature conditions and carrying out microbial and enzymatic activities. The amount of fish peroxide was changed during the ice-cover period, with the lowest amount observed on the tenth day, and then increased again. But in all periods of testing, its value was lower than the standard. The reason for the increase in peroxide is the increasing the effect of lipase on fat and its conversion into fatty acid and the conversion of fatty acid to peroxide. Reducing the amount of peroxide is probably due to the effect of some cellular compounds in the muscle of the fish, which in this way prevents the progress the fat oxidation. The researchers report that in different species of fish, decreasing the amount of protein by increasing the storage period in the vicinity of ice is likely due to protein degradation and its increase is due to the reversibility of this process. It is concluded ice cover prevents from spoilage until fourth day only. The fish storage period in affected on the fish nutrient composition and it decreased fat and ash contents and increased moisture content. Based on the results of this study, although ice use is a cheap and effective way to reduce temperature and storage of fish, but long-time storage in ice has reduced the quality and fish nutrition value.