The effect of edible coating based on Althaea officinalis mucilage containing orange (Citrus sinensis) peel essential oil on microbial properties of rainbow trout fillet (Oncorhynchus mykiss)

Fresh fish is highly perishable due to its high water activity, availability of nutrients, almost neutral pH (factors affecting microbial growth) and the presence of autolytic enzymes. In this regard, the use of films and edible coatings containing antimicrobial compounds in fresh fish can prevent microbial growth and prevent the formation of chemical metabolites. In this study, the effect of Althaea officinalis mucilage coating containing of 0, 0.25 and 0.5% of orange peel essential oil on preventing the growth of microbial flora of fish fillets in the refrigerator was investigated during 16 days of storage. The results showed that with increasing the orange peel essential oil, the L* index and elongation at break of the films increased and the b* and a* indices, elastic modulus and of the tensile strength decreased (p <0.05). Also, during storage, the number of aerobic mesophilic bacteria, psychrophilics, lactic acid and coliforms and pH increased significantly in all fish fillet treatments, which was less in the treatments with mucilage coating containing orange peel essential oil (p <0.05). According to the existing standards, the maximum number of aerobic mesophilic bacteria, psychrophilics, lactic acid and coliforms in rainbow trout is set at 7, 7, 6 and 4 log cfu/g, respectively. Based on this, it is possible to prevent the increase of microbial load to above the standard level by using the Althaea officinalis mucilage coating until the fourth day, with the coating containing 0.25 and 0.5% essential oil until the eighth and twelfth days, respectively.