Effects of Alginate Coating Containing Zataria multiflora Essential Oil in the Form of an Emulsion Gel and Nano-emulsion on the Chemical Quality and Sensory Properties of Rainbow Trout Fillet

Fish is often more perishable than most other foodstuffs. Microbial progression, enzymatic activity, and non-enzymatic oxidation of fats reduce the quality of fish and its products. The present study aimed to evaluate the effects of the nano-gel emulsion and emulsion gel of an alginate coating containing Zataria multiflora essential oil (ZMEO) on the chemical and sensorial quality of rainbow trout fillet (Oncorhynchus mykiss) during 16 days of refrigerated storage (4±1°C). The fish fillets were treated with alginate coating, alginate emulsion with different ZMEO concentrations (E0.25%, E0.5%, and E1%), and nano-emulsion with different ZMEO concentrations (N0.25%, N0.5%, and N1%). Afterwards, the fillets were analyzed for chemical changes (pH, TVB-N, TBARS, PV, FFA, and fatty acid profile) and sensory properties (color, texture, flavor, odor, and overall acceptability) on days zero, four, eight, 12, and 16. Data analysis was performed in SPSS version 21 using ANOVA, Bonferroni post-hoc test, and Dunnett T3 test to assess significant differences at P<0.05. The results of chemical analysis showed an increasing trend (pH, TVB-N, TBARS, PV, FFAs, MUFAs, and SFAs) during the storage period (day 16) although the rate was slower in the nano-emulsion treatments. Furthermore, the sensory properties of the samples decreased during the storage period, while using ZMEO in the alginate coating (especially in the nano-emulsion form) showed better results compared to the control. According to the results, the alginate coating containing ZMEO (especially in the nano-emulsion form) could preserve the chemical and sensorial quality of the fresh trout fillets for four days.