Effects of heat treatment on chlorophyll degrading enzymes in stored broccoli (Brassica oleracea L.)

Abstract

Abstract Effects of heat treatment on chlorophyll (Chl) degrading enzyme activities in stored broccoli ( Brassica oleracea L.) were determined. Chl contents of broccoli treated at 50 °C for 1 h or without heat treatment (control) decreased after 4 days of storage at 15 °C, whereas the contents of broccoli treated at 50 °C for 2 h showed almost no change after 4 days of storage at 15 °C. Chlorophyllase activity of broccoli heat-treated for 1 or 2 h decreased during storage before the occurrence of yellowing, while the activity of the control showed a slight decrease on day 4. Chl oxidase activity of broccoli heat-treated for 2 h remained unchanged. Chl degrading peroxidase activity in the control markedly increased after 6 days of storage at 15 °C, but an increase in the activities in broccoli treated at 50 °C, especially for 2 h, was suppressed. Six anionic and two cationic isoperoxidases were detected in broccoli on day 0. One of the isoperoxidases, C 2 (Rf 0.3) cationic isoperoxidase, was involved in Chl degradation and the increase in C 2 level was greatly reduced by treatment at 50 °C for 2 h. These results indicate that heat treatment could reduce Chl degradation due to the suppression of Chl degrading enzyme activities.