Inhibition of Yellowing and Ethylene Production in Broccoli Florets following High Temperature Treatment with Hot Air

Abstract

High temperature treatment (HTT) with hot air at 45, 50 or 55°C for 1 to 5 hr prior to storage at 20°C was conducted to delay the yellowing of harvested broccoli florets. HTT at 50°C for 2 and 3 hr were more effective than others for maintaining green color and good quality of broccoli florets. Loss of chlorophyl and increase of carbon dioxide and ethylene production in the florets during storage at 20°C were inhibited by HTT at 50°C for 1, 2 and 3 hr except for the chlorophyll loss of 1 hr treatment. Inhibitions rates increased with in duration of HTT. 1-aminocyclopropane-1-carboxylic acid (ACC) content in florets during storage increased with the same rates in the control and HTT at 50°C for 1 and 2 hr, but the HTT for 3 hr retarded the increase in ACC content. Activity of ACC oxidase in the florets during storage increased remarkably in the control and HTT at 50°C for 1 hr, followed by those with the HTT for 2 hr, which reached maxima and subsequently declined quickly to low levels. However, in the florets with HTT at 50°C for 3 hr, scarcely any enzyme activity was detected during storage. These results suggest that HTT at 50°C for a short-term period would inhibit the conversion of ACC to ethylene and reduce ethylene production resulting in the retardation of yellowing in broccoli florets.