The effect of biocomposite coating based on Opopanax mucilage and gelatin containing zinc oxide nanoparticles enriched by peppermint (Mentha piperita L) essential oil on the microbial and sensory properties characteristics of rainbow trout (Oncorhynchus mykiss)

Considering the possible adverse effects on the sensory properties of food due to the use of essential oils in effective concentrations for antimicrobial and antioxidant activity, the use of combined methods can be effective. In this study, the effect of coating combination of gelatin and Opopanax mucilage containing 0.5% zinc oxide nanoparticles, enriched by concentrations of 0, 1.2, 1.6, and 2.0 % of peppermint essential oil and modified atmospheric packaging (MAP) on preventing the growth of microbial population rainbow trout fillets were evaluated during 20 days of storage in the refrigerator. The results showed that in all treatments the number of aerobic mesophilic bacteria, psychrotrophs, lactic acid bacteria, and coliforms as well as pH increased during the storage period but decreased by increasing peppermint essential oil (p<0.05). Also, the microbial load in treatments with a coating containing nanoparticles and MAP was significantly lower than in the control sample (p<0.05). The results of sensory evaluation also showed that the odor and color scores of the samples decreased during storage, which was the highest in the control and the lowest in the NPEO3 treatment (p<0.05). The results of the sensory evaluation were consistent with the results of microbial analysis. According to the results obtained in this study, using the mixture of 0.5 % zinc oxide nanoparticles and 50% peppermint essential oil in edible coating composed of Opopanax mucilage and gelatin for increasing the shelf life of rainbow trout fillet up to the 15th day is recommended.