Abstract
Effects of light on the chlorophyll (Chl) degradation in stored broccoli (Brassica oleracea L. var. italica Plen.) florets after blanching were studied. Chl contents decreased greatly during storage at 10°C in the light (30 μmole · m-2 · s-1), whereas original levels of Chl were maintained in the dark. Small amounts of 132-hydroxychlorophylls a and b (Chls a-1 and b-1), an oxidized form of Chls a and b, were formed during storage in the light with Chl degradation. Chls a′ and b′, isomers of Chls, and pheophytins a and b were formed after blanching and the proportions of these derivatives increased during storage in both light and dark. L-Ascorbic acid and α-tocopherol contents decreased greatly during storage in the light, whereas thiobarbituric acid values increased. Activity levels of lipoxygenase, chlorophyllase and Chl degrading peroxidase became very low after blanching and showed almost no change during storage in the light and the dark. This suggests that active oxygens formed nonenzymatically on the Chl pigment might act effectively on Chl degradation due to decline in the protection of antioxidants.
