impacts of nano-gelatin coating containing thymol and nisin on chemical quality indices of rainbow trout fillets stored at 4°c

Background: seafood such as fish is an integral part of human nutrition and an excellent source of protein. however, their short shelf life is quite challenging for the food industry. objectives: this study was carried out to investigate the effects of nano-gelatin coating embedded with thymol and nisin on the chemical quality indices of rainbow trout fillets during 16 days of storage at 4°c. methods: the fillets were randomly divided into six groups, including control (c), gelatin (g), nano-gelatin (ng), nano-gelatin + thymol (ng-t), nano-gelatin + nisin (ng-n), and nano-gelatin + nisin and thymol (ng-t-n). the chemical quality of fish samples was assessed by performing ph, thiobarbituric acid reactive substance (tbars), peroxide value (pv), free fatty acid (ffa), and total volatile basic nitrogen (tvb-n) analyses every four days. results: the results revealed the stunning effect of nisin and thymol addition to the nano-gelatin coating on all chemical quality indices. besides, pv, tbars, and ffa analyses showed that nano-gelatin containing thymol significantly decreased lipid oxidation in fish fillet samples (p < 0.05). the lowest amounts of pv (8.33 meq oxygen/kg oil), tbars, and ffa were recorded for ng-t-n. the best results in the tbars test (p < 0.05) were observed in ng-t-n, followed by ng-t (1.45 and 1.69 mg of malonaldehyde/kg of tissue, respectively), and similar results were recorded for ffa analysis. on day 16, the lowest amounts of tvb-n were measured for ng-t-n, followed by ng-n and ng-t (26.13, 29.86, and 38.26 mg n/100 g, respectively). both nisin and thymol reduced the tvb-n and increased the shelf life, and the best results were observed in groups treated with nisin and thymol simultaneously. however, the application of gelatin and nano-gelatin coating without nisin and thymol was ineffective in improving the chemical quality of samples, and they must be used with nisin and/or thymol. conclusions: gelatin nanogel embedded with thymol and nisin can be utilized to enhance the chemical quality and shelf life of fish fillets.