Combination effects of Lemon essential oil and chitosan nano-emulsion on enzyme activity, antioxidant capacity and phytochemical content of Raspberry fruit

Due to high softness and water content, Raspberry fruit is very perishable and highly sensitive susceptible to fungi leading to a very short shelf life.In this study, the effects of a nano-chitosan based coating in combination with lemon essential oil on extending the shelf life of raspberry were studied. Harvested raspberry fruits were treated with lemon essential oil at 0, 250, 500 and/or 750 μl/l, and then coated with chitosan nano-emulsion at 0, 2500and 5000mg/l and stored at 4±2̊С with 85-95% RH. Total phenolics and flavonoid content, the concentration of anthocyanins, the antioxidant activity and the activity of PAL and guaiacol peroxidase enzymes were evaluated every three days.The PAL activity and anthocyanin content offruit treatedwere significantly higher. The highest PAL activity (136.55 nmolesmin−1mg−1of fresh weight) and anthocyanin content (129.22 mg cyanidin 3-galactoside equivalent/1 mLjuice) were observed in the 500μll-1EO×2500 mgl-1CH and 750μll-1EO×5000 mgl-1CH treatments on the 9th day, respectively. Also the highest total phenolic content (57.53 mg GAE/1 mLjuice)was observed in the control treatmenton the 9th day. The values of total flavonoid content showed a downward trend over the storage period for all treatments.Coating the perishable fruits of raspberry with a nano-chitosan based coating containing lemon essential oil is introduced as a safe treatment for increasing the phytochemical compounds such as total phenolic and flavonoid contents and the activity of the enzymes involved in the biosynthesis of phenolic compounds such as PAL.