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The aim of this study was to investigate the effect of chitosan as a natural preservative. Farmed fish were washed and filleted. In this study, 3 types of chitosan were investigated: acid-soluble chitosan, water-soluble chitosan and oligosaccharide chitosan. The fillets were immersed in the above solutions for 30 seconds, and then removed, and after 2 minutes, the immersion was repeated. Control samples were uncovered. The fillets were then placed at room temperature (20 °C) for 2 hours to form a coating on the fillets. 192 pieces of 100 g fish fillets were divided into 4 treatments and each treatment was divided into 4 times: treatment one as a control (without preservative), the second treatment containing 1% acid-soluble chitosan, the third treatment containing 1% water-soluble chitosan and the fourth treatment containing 1% Chitosan oligosaccharides. All samples were stored in refrigerator at 4±1 °C and their chemical parameters (Peroxide, pH, Thiobarbituric acid, Total Volatile Nitrogen) were measured on (0, 4, 8 and 12) days. All the indices of treatments had increasing trend over time. Only in the pH index of 1% acid-soluble chitosan had an irregular trend. 1% acid-soluble chitosan had the most positive effect in all treatments. Due to increase in chemical indices in all treatments, the addition different of chitosans to fish fillets could prevent or reduce them.

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In this study, the effect of bay laurel and rosemary leaf extracts in two forms, free and nanoliposome, on the chemical indices of spoilage (TVB-N) and (TBA) in minced Silver carp fish was investigated. Extracts were evaluated for phenolic and flavonoid compounds. The treatments studied in minced Silver carp fish included control treatment, treatments containing 1 and 1.5% of free extract of Laurus nobilis leaves and Rosemary and treatments containing 1 and 1.5%. It is one of the liposome-coated extracts that was tested at refrigerator temperature at 0, 4, 8 and 12 days with 3 replications. The results showed that the amount of phenolic and flavonoid compounds in rosemary extract was more favorable than fragrant leaves. The aqueous extract of rosemary had higher levels of phenolic (344.66 mg gallic acid / g extract) and flavonoid (245.33 mg Rutin / g extract) compounds compared to the bay laurel extract (257.66 mg gallic acid / g extract) and (151.26 mg Rutin / g extract) respectively. The results of chemical changes in minced Silver carp showed that with increasing the storage time of fish at refrigerator temperature, the mentioned parameters increased, but nevertheless, in the treatment containing the finely coated form of two plants, Laurus nobilis leaves and rosemary (concentration 1.5%), The changes were significantly slower than other treatments, and according to the results, it can be concluded that in general, the addition of extracts Odor of Laurus nobilis and rosemary leaves in a concentration of 1.5%, maintains the quality of Silver carp fish in terms of chemical quality indicators.