Effect of combined application of Pimpinella affinis essential oil and extract in zein edible coating on vacuum packaged rainbow trout fillet quality

In the present study, the antioxidant and antimicrobial effects of essential oil (EO) and extract of Pimpinella affinis on the shelf life of rainbow trout during storage at refrigerator temperature based on three indicators of microbial, chemical and sensory quality parameters were evaluated. For this purpose, fish samples were stored in zein coatings containing 1.00% EO and 2.00% extract and in combination treatment containing 1.00% of each of them in refrigerator for 12 days. All of treatments were analyzed for microbiological count (Enterobacteriaceae, psychrophilic bacteria, mesophilic bacteria and pseudomonas bacteria) and chemical including pH, thiobarbituric acid reactive substances (TBARS), total volatile base nitrogen, peroxide value (POV) and free fatty acids (FFAs) and sensory (odor, color and texture) characteristics. Results showed that the highest levels of three factors including TBARS, POV and FFAs were related to the control sample and the least amount of these parameters was observed in EO and extract combination treatments. This effect of combined treatment was also observed in the reduction of total volatile basic nitrogen and pH parameters. Total bacterial counts during storage in fish treated with the extract and EO were remained below the acceptable level and microbial spoilage was significantly decreased compared to control. According to the sensory evaluation, treatments containing EO and extract showed improvement in this index compared to control treatment during storage. Based on the results of this study, it can be concluded that the EO and extract of p. affinis as active ingredients in zein coating successfully improve the quality and shelf life of the fish in the refrigerator.