Nutritional impact of phytosanitary irradiation of fruits and vegetables
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5.6Other fruitPublished data were not identified for the effects of irradiation on honeydew melon and watermelon. Effects of irradiation on grapes, melons, kiwifruit and persimmons are summarised below and in Table 6.6. Grapes A study of three grape cultivars assessed the effects of irradiation with 2, 2.5 and 3.5 kGy, as well as the combined effect of a hot water dip (50C, 5 min) with irradiation at 1 kGy (Thomas et al. 1995). AA levels were measured both immediately and after storage at different temperatures. In Thompson seedless grapes, irradiation with 2 kGy decreased AA by 28% to 41% compared to non-irradiated grapes. The combination of hot-water dip and 1 kGy irradiation had a similar effect on AA, with decreases of 13% to 60%; however, it is not possible to separate the effects of irradiation from that of the heat-treatment on AA levels in this group. In another two cultivars, grapes were irradiated with 2.5 and 3.5 kGy and AA measured after 1 and 56 days storage at 10C. In Sonaka grapes, irradiation at both doses initially increased AA by 13-18%, but after storage levels were ~13% lower in irradiated fruit. Tas-A-Ganesh grapes showed the opposite pattern, with AA levels initially 7-10% lower in irradiated grapes, but AA levels were 8-11% higher after 56 days storage. It is important to note that no statistical analyses were presented in this paper, thereby limiting the interpretation of these results. Unpublished data from DAFF QLD (2012) found no significant effect of irradiation with 0.15, 0.6 and 1.0 kGy on total vitamin C or -carotene levels in grapes either one day after irradiation or after 50 days storage at 0C. Melon Irradiation of muskmelon (rockmelon, cantaloupe) with 0.5 and 1.0 kGy had no significant effect on vitamin C levels in fruit studied from four harvests over two consecutive years (Lalaguna 1998). Similarly, irradiation of fresh-cut rockmelon with 0.5 Gy had no significant effect on AA levels after 1, 3 and 7 days (Fan et al. 2006). Unpublished data from DAFF QLD (2012) found no significant effect of irradiation with 0.15, 0.6 and 1.0 kGy on vitamin C content of rockmelon and honeydew melon, either one or 14 days after irradiation. Similarly, -carotene levels were not significantly changed in irradiated rockmelon. In contrast, -carotene levels were significantly decreased in irradiated honeydew melon one day after irradiation, but after 14 days storage there was no significant difference and levels tended to be higher in irradiated compared to non-irradiated melons. Kiwifruit Irradiation of mature, unripe kiwifruit with 1 and 2 kGy had no effect on AA levels, but levels decreased significantly with 3 kGy (~10%) (Kim and Yook 2009). After 1-3 weeks storage, AA levels increased in all fruit, but were significantly lower in all irradiated fruit compared to non-irradiated fruit. However, in this study only AA levels were measured; the small differences in AA content between irradiated and control fruit could be due to conversion to DHAA. Antioxidant activity was similar between control and irradiated kiwifruit throughout the storage period, with the exception of a small (<10%) but significant decrease immediately after irradiation with 2 and 3 kGy. Persimmon Irradiation of persimmons with 0.075 and 0.3 kGy had no effect on total vitamin C content either immediately or after 3 weeks storage; vitamin C increased ~2-fold with storage in both control and irradiated persimmons (Mitchell et al. 1992). Table 6.6 Effects of irradiation on radiation-sensitive nutrients in grapes, kiwifruit, persimmon and rockmelon.
*Significant difference. n.d.: not determined. Yüklə 295,98 Kb. Dostları ilə paylaş:
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