Investigation of antioxidant edible coating and modified atmosphere packaging for enhancing storability of hazelnut kernels

This study investigated the effects of antioxidant edible coating and modified atmosphere packaging for improving storability of dried hazelnut kernels by delaying lipid oxidation and color degradation. Hazelnut kernels were coated with different coating matrix (methylcellulose and chitosan) that contain different antioxidant substances (DL-α-tocopherol acetate, cinnamon essential oil, rosemary essential oil and hazelnut oil) and subjected to an accelerated storage condition at 35 °C for 270 days. Hazelnut kernels were also packed under modified atmosphere (MAP) with 100 % N2 in mylar bags and stored at 35 °C for 180 days. Lipid oxidation (free fatty acids, K232 and K270, peroxide values) and color (browning index) were measured for investigating quality changes during the storage. The free fatty acids of kernels from two packaging experiments remained stable during storage. K232 value of MAP kernels was significantly lower (2.20) than that of control (2.90) at the end of the storage, showing delayed production of conjugated dienes. The chitosan based edible coating with encapsulated cinnamon essential oil and oleic acid (CH/ECO/OA) resulted in significantly (P<0.05) lower PV values (0.53 meq/kg oil), and all the coated samples had the positive effect on reducing browning index with 12-25 compared with control. K270 (0.04-0.18) remained relatively low throughout the long-term storage. As a result, modified atmosphere packaging performed better than edible coatings. This study demonstrated the importance of implicating proper postharvest technology for reducing lipid oxidation and quality deteriorations of hazelnut kernels during prolonged storage.