Ethanol Inhibits Ripening of Tomato Fruit Harvested at Various Degrees of Ripeness without Affecting Subsequent Quality

Abstract

Tomato fruit (Lycopersicon esculentum Mill., cv. Castelmart) were harvested at various degrees of ripeness and exposed to ethanol vapor at 0, 2, or 4, ml·kg-1 in a 20-liter jar for 0, 2, 4, or 6 hours at 20C. Ripening was measured as changes in subjective color and in firmness and production of CO2 and ethylene. The soluble solids concentration (percent), titratable acidity (percent), and pH were measured at the end of the storage period when the fruit were red-ripe. Ethanol's inhibition of ripening was not confined to mature-green fruit, but also inhibited reddening of breaker, turning, and pink fruits. Storage of mature-green fruit at 20, 15, or 12C after treatment with 0 or 2 ml ethanol/kg at 20C prolonged the delay in ripening for 5, 6, and 7 days, respectively, compared with controls. There was no reduction in the quality of these fruit when they were red-ripe, even though there was an 11-day difference between the time the 20C control and the 12C-treated fruit became red-ripe. An informal panel did not detect any differences in flavor between these control and ethanol-treated fruit that were red-ripe. Increasing the duration of exposure to ethanol vapors from 2 to 6 hours had a pronounced effect on ethylene and CO2 production, but it did not significantly prolong the inhibition of ripening of mature-green fruit nor did it change their rate of softening during ripening. Increasing the temperature during exposure increased the effectiveness of ethanol, with the same level of inhibition produced by 6 hours at 20C, 4 hours at 25C, or 2 hours at 30C. Postharvest use of ethanol vapor to retard ripening may be a useful technique to extend the market life of tomato fruit.