Effects of ethylene and 1-methylcyclopropene on the postharvest qualities of 'Shamouti' oranges

Citrus fruits are nonclimacteric and produce only low amounts of ethylene. However, exogenous applied, and possibly endogenous ethylene, may be involved in the regulation of fruit maturation and senescence. We examined the effects of ethylene and 1-methylcyclopropene (1-MCP), an ethylene action inhibitor, on the postharvest qualities of 'Shamouti' (Citrus sinensis L. Osbeck) oranges. Neither ethylene nor 1-MCP had any effects on the loss of fruit weight and firmness. However, ethylene had disadvantageous effects on most other postharvest parameters. It increased the appearance of chilling injury (CI) symptoms, stem-end rot decay, and the content of volatile off-flavours in the juice head space and fruit internal atmosphere. The only protective effect of ethylene during postharvest storage was in reducing the amount of decay caused by mold rots. 1-MCP treatment effectively inhibited the ethylene effects on 'Shamouti' oranges, as indicated by blocking of the degreening process, but was ineffective in restoring the negative effects of ethylene during storage; it even weakened the tissue and increased CI symptoms, decay development, and the accumulation of volatile off-flavours. It is concluded that while high concentrations of exogenous applied ethylene are undesirable during storage, and enhance fruit deterioration, the small amounts of endogenous ethylene produced by the fruits may be required to maintain their natural resistance against various environmental and pathological stresses. In future, we suggest that 1-MCP may be applied as a postharvest treatment to inhibit the degreening process in citrus fruits which are preferably marketed green, but special care must be taken to avoid CI and decay development. (C) 1999 Elsevier Science B.V. All rights reserved.