Interaction effects of natural antioxidants coating and various packaging on walnut kernel during storage at 25 °C

Abstract

Increasing the walnut shelf life with non-synthetic materials is considered. The effect of edible coating and different packaging methods on physicochemical properties of Persian walnut kernel during 120 days of storage at 25 °C temperature was evaluated. The treatments were: C (control sample, uncoated), K (coated with 1 % chitosan) and K500 and K1000, coated with chitosan 1 % containing 500 and 1000 μL L-1 of thyme essential oil, respectively, and MP (Mass packaging), PP (packaging in Polypropylene bags) and AP (Active packaging using sachets made by ascorbic acid, sodium bicarbonate and iron oxide). The color properties and oxidation of walnuts have relationship together. The results showed that the amount of a* and b* values were in the following order: K1000> K500> K> C. At the end of storage L* value of all samples decreased. Coated samples had less peroxide value and free fatty acid than control. Amount of free fatty acid in the coated samples with mass packaging was less than 0.5 %. The moisture content of coated samples was more than control samples, active packaging and PP packaging had minimum moisture fluctuations respectively, and control sample had less amount of moisture.