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Effect of heat treatment on catabolites formation in relation to chlorophyll degradation during stroage of broccoli (Brassica oleracea L. Italica group) florets
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The effects of heat treat ent on the formation of chlorophyll (Chi) derivatives and Chi-degrading enzyme activities in stored broccoli (Brassica oleracea L. Italica Group 'Ryokutei') florets were determined. The Chi a level barely changed during heat treatment, but each Chi a derivative level changed. Chlorophyllide (Chlide) a, pheophorbide (Pheide) a, C132-hydroxychlorophyll (C132-OHChl) a, Chi a', an isomer of Chi a, and pheophytin (Phy) a were detected as a Chi derivative during heat treatment and during storage after treatment. Chlide a, Pheide a, and C132-OHChl a levels decreased during 2-h heat treatment (50°C), whereas Chi a' and Phy a levels increased. Chl-degrading enzyme activities, in particular, Mg-dechelation activity, were effectively suppressed after 2 h of heat treatment. The content of Chis a and b in control broccoli florets decreased greatly during storage at 15°C, while the content in heat-treated broccoli florets hardly changed at all. In Chi derivatives, the Pheide a level in broccoli florets treated with or without heat treatment, especially the former, increased appreciably during storage. The Chlide a level in control florets decreased markedly during storage. On the other hand, the Chlide a level in heat-treated broccoli florets did not change during storage. Mg-dechelation activity in control florets markedly increased after 4 days of storage at 15°C, but the enhancement of the activity was suppressed by heat treatment. These findings suggest that Chi derivatives, especially Pheide a, are accumulated as intermediates in heat-treated broccoli florets, and Mg-dechelating action, in conjunction with that of chlorophyllase and Chi-degrading peroxidase, could be involved in Chi degradation in stored broccoli florets.
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 Record created 2007-11-06, last modified 2019-06-17

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