Changes of Aroma Character of Irradiated Onion during Storage

Abstract

γ-Ray irradiation of fresh onion is useful method to prevent sprouting during storage. WHO/FAO have approved of 0.15 kGy irradiation to fresh onion for this purpose. Aiming at the wholesome-ness of food irradiation, we tried to compare the aroma constituents of irradiated onion during storage. Irradiated onions (0.2, 5.0kGy) were stored for 3 months and their aroma characters were assayed at regular intervals by head space vapor analysis with a thermal desorption cold trap (TCT) injection system. The chemical structures of twenty two compounds were identified or estimated. The gas chromatograms (GC) obtained from the onions irradiated at a dose of 0.2kGy were almost the same as those of non-irradiated onion during all the stages of 3months storage. The onions irradiated at a dose of 5.0kGy showed higher contents of disulfides and trisulfide on their GC. The similarities among GC patterns obtained from all these samples were calculated using 44 peaks strength commonly appearing on each GCs as respective variables for mathematical treatment. The result showed that GC patterns of 0.2kGy irradiated samples were almost similar to those of non-irradiated ones quantitatively. However, similarities between 0.2kGy and 0.5kGy irradiated samples were lower than those between non- and 0.2kGy irradiated onions. These results suggest that under the permitted irradiation, fresh onion does not show any changes in the aroma constituents which are the most unstable flavor components in onion.