Ethylene synthesis in mango fruit following heat treatment.
Ketsa S., Chidtragool S., Klein J. D., Lurie S.
Author Affiliation: Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand.
Postharvest Biology and Technology 15 : 65-72
Abstract : Mango fruits (cv. Nam Dokmai) were placed directly at 25°C after harvest or were held for 3 days at 38°C and then transferred to 20°C. Fruits placed directly at 25°C reached their peak ethylene production after 4 days, while the heated fruits reached their peak ethylene production after 9 days (6 days after the end of the heat treatment). The 1-aminocyclopropane-1-carboxylic acid (ACC) content paralleled that of ethylene production in unheated fruits, with the highest content occurring on day 4. In heated fruits, ACC content continued to increase for 8 days following heat treatment. The 1-aminocyclopropane-1-carboxylic acid synthase (ACS) activity in unheated fruits was also highest on day 4. In heated fruits, ACS activity was undetectable following heat treatment, but recovered partially during the ripening period. Initial ethylene production from discs with peel was 6-fold higher in unheated fruits than heated fruits, although after 6 h of incubation the production from both was similar. Activity of 1-aminocyclopropane-carboxylic acid oxidase (ACO) in the discs also showed an 8-fold difference in initial activity in heated versus unheated discs with peel. This difference disappeared during incubation of the discs. In heated discs without peel, both ethylene and ACO activity remained lower than in discs with peel, and the differences between heated and unheated fruit discs were more pronounced. It is concluded that the inhibition of ethylene production found during heat treatment is due to inhibition of both ACS and ACO. ACO recovers full activity following heat, while ACS activity recovers only partially, but enough to allow the heated fruits to achieve an ethylene peak.