Effect of γ-irradiation on the physicochemical and sensory properties of fresh walnut kernels (Juglans regia) during storage

Abstract

The current study examined the total phenol content, antioxidant activity, sensory quality and fatty acid composition of fresh walnut kernels as a function of irradiation dose to determine dose levels that resulted in the least amount of undesirable changes to fresh walnut kernels at regular intervals of time. Fresh walnut kernels were exposed to 60Co radiation at doses of 0.5, 1.5, 3, 6, 8, and 10 kGy and stored at ± 4 °C for 28 days. Irradiation doses of 0.5 and 0.1 KGry have no significant effect on total phenol content (1.56±0.04–1.30±0.02mgGAE/g), antioxidant activity (95±0.02–85±0.01%), peroxide value (0.49±0.04–0.72±0.03%) and free fatty acid values (0.14±0.01–0.29±0.03%) respectively. However, irradiation doses of 1.0, 2.0, 3.0 and 4.0 resulted in increased peroxide values (0.89±0.02%, 0.98±0.01%, 1.05±0.01%, 1.17±0.03%), increased free fatty acid values(0.05±0.01%, 0.58±0.03%, 0.63±0.02±0.01%, 0.67±0.04%) and also the organoleptic quality were decreased (2.0 ± 0.01, 1.7 ± 0.03, 1.4 ± 0.02%, 1.2 ± 0.03%) during 28 days of storage. The use of gamma irradiation appears to be a promising technology for improving the chemical quality of fresh walnut kernels, but food safety concerns must be addressed before it can be recommended as a useful conservation alternative.