Evaluation of antimicrobial and antioxidant effect of sodium caseinate edible coating enriched with rosemary essential oil (Rosmarinus officinalis) on the quality and shelf life of rainbow trout (Oncorhynchus mykiss) during refrigerated storage

The aim of this study was to investigate the effects of sodium caseinate (SC) edible coating enriched with Rosmarinus officinalis essential oil on the quality and shelf life of rainbow trout (Oncorhynchus mykiss) during 20 days of refrigerated storage (4±1˚C).  Aqueous solutions of sodium caseinate (SC) 8% (w/w) were prepared in the form of 4 treatments of SC without essential oil and SC with rosemary essential oil in three concentrations (0.25%, 0.5% and 1% (v/w)), then applied as a coating on the rainbow trout and refrigerated for 20 days, and every 4 days, chemical (pH, total volatile basic-nitrogen, thiobarbituric acid and peroxide value) and microbiological (total viable count and psychrotrophilic count) analysis were performed on them. The results showed that control samples exceeded the acceptable limit of microbiological and chemical values on around days 12, while SC+1%R samples exceeded the acceptable limit after 16 days of storage and did not exceed the peroxide value and thiobarbituric acid limit even after 20 days of storage. This study showed that Sodium casein coating has an inhibitory property against oxygen and the use of rosemary essential oil in its composition reduces the oxidative, chemical and microbial spoilage of rainbow trout.