Effects of gamma irradiation on chemical and sensory characteristics of natural hazelnut kernels

• Hazelnut kernels were treated with 0, 0.5, 1 and 1.5 kGy of gamma irradiation.
• Examine chemical and sensory changes in irradiated hazelnuts.
• Contribute to broaden the use of this technology in food stuff.
• Optimal irradiation dose of 0.5 kGy for hazelnut kernel was obtained.

In present study, natural hazelnut kernels were treated with, 0.5, 1 and 1.5 kGy of gamma irradiation. The irradiated and untreated hazelnuts were stored at 20 ± 0.5 °C and 55–60% relative humidity for 18 m. After irradiation, 0.5, 1 and 1.5 kGy doses of gamma irradiation significantly increased the total fat values (p < 0.05) and this value decreased during the storage. After treatment, free fatty acid values were similar in untreated and treated hazelnuts. After 6 m of storage, irradiated and untreated hazelnuts had less than 1% free fatty acid values. However, control and 1.5 kGy yielded higher than 1% free fatty acid after 9 m of storage. After irradiation, peroxide values increased proportionally to the dose but the increase was not significant. Peroxide values increased during the storage period (p < 0.05). Control and 0.5 kGy-treated hazelnuts had maximum peroxide values after 9 m of storage, while 1 kGy and 1.5 kGy-treated hazelnuts had maximum levels after 12 m of storage. Applied doses did not cause any significant changes in crude protein, water activity (aw), crude cellulose and moisture content of hazelnuts (p > 0.05). Storage period significantly affected the water activity and crude cellulose (p < 0.05). Irradiation doses didn’t affect the L*, a* and b* values (p > 0.05), but storage period significantly affected the color values (p < 0.05). At the end of storage period, L* and vitamin E values decreased proportionally to the dose.The 0.5 kGy-treated hazelnuts had the lowest free fatty acid and peroxide values and such a case also reflected in sensory analyses. Furthermore, these hazelnuts had the highest vitamin E value after the control group. Application of 0.5 kGy gamma irradiation seems to be acceptable for natural hazelnut kernels, but food safety issues have to be evaluated in order to recommend its application as a useful conservation alternative.