Influence of ultraviolet radiation treatment on the stability of bioactive compounds and antioxidant activity in leafy vegetables throughout refrigerated storage

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Different vegetables are considered as sources of human health promoting components. Leaf vegetables are widely used in human diet for many reasons including their very high in bioactive compounds with physiological significant roles. Irradiation is a non-thermal preservation method which involves the exposure of food materials or products to radiation, for example ultraviolet (UV-C) rays. This research was carried out to study the influence of ultraviolet radiation treatment on the stability of bioactive compounds and antioxidant activity in leafy vegetables throughout refrigerated storage.  The analysis of variance for the total phenolics (TP), carotenoids (TC) and chlorophyll (TCP) levels indicates that their values were significantly (P < 0.05) affected by both the UV-C radiation and the refrigeration storage period. Initial TP, TC and TCP values for all UV-treated samples were significantly lower (P < 0.05) than those for the control samples. When all leafy vegetables were included in the statistical analysis, there was a positive significant (p≤0.05) relationship between total phenolics (r2 = 0.584), total carotenoids (r2 = 0.385), total chlorophyll (r2 = 0.312) and antioxidant activity in control and UV-treated samples throughout refrigerated storage. Also, bacteriological analysis indicated that total aerobic bacterial growth (TABG) of spinach, lettuce and chicory was recorded 5.51, 4.88 and 4.56 log10 cfu/g which increased by rates of 58.11, 61.47 and 69.30% for the untreated samples and 31.80, 34.15 and 34.93% for the UV treated samples after 8 days of refrigeration at 4 0C, respectively.In conclusion, UV-C treatment brings some benefits to the fresh cut industry  of  leafy vegetables (spinach, lettuce and chicory) including prolonged their shelf lifebased on total microbial counts but some reducing in an important bioactive compounds i.e. phenolics, carotenoids and chlorophyll have been reduced. Such notice should be taken in our consideration when the UV-treated leafy vegetables will be used as functional foods and/or in diets planning

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