Effect of 60Co-γ Irradiation on Postharvest Physiology and Lipid Nutrition of Fresh Hazelnuts

Fresh hazelnuts were treated by 60Co-γ irradiation (0, 0.25, 0.50, 0.75 and 1.00 kGy) and stored at (4.0 ± 0.5) ℃ for up to three months. Changes in physiological indexes and lipid nutrition were monitored during the storage period. The results showed that irradiation at a dose of 0.25–1.00 kGy delayed the decline in superoxide dismutase (SOD) and catalase (CAT) activity, and reduced the activity of polyphenol oxidase (PPO) in fresh hazelnuts. The irradiation dose of 0.50 kGy was the most effective, and at the end of storage, the respiratory intensity, malondialdehyde (MDA) content and lipoxygenase activity of the irradiated sample decreased by 25.81%, 18.50% and 4.18% compared with those of the non-irradiated one, respectively. However, irradiation had no significant effect on fatty acid composition and content, peroxide value (POV) or acid value (AV). Principal component analysis (PCA) performed on fresh hazelnuts stored for 90 d also showed that 0.50 kGy 60Co-γ irradiation imparted the best storage quality to fresh hazelnuts. These results suggest that 60Co-γ irradiation can delay the senescence and effectively extend the shelf life by affecting the postharvest physiology of fresh hazelnuts.