Ethanol controls postharvest decay of table grapes

Postharvest deterioration of table grapes generally results from berry decay and/or desiccation of stems and pedicels. Conventional methods to avoid these problems include SO 2 fumigation or release from generator pads containing a metabisulfite salt, and packaging of the fruit in polyethylene liners. SO 2 is usually effective in preventing decay as long as its level is sufficiently high. However, high levels can result in fruit damage, unpleasant aftertaste, and allergies. Our objective was to examine the effect of applying a postharvest ethanol dip on the decay of table grapes. Immersion of detached berries in 70% ethanol eliminated most of the fungal and bacterial populations on the berry surface, but had little effect on survival of yeasts. In vitro development of spores of the major postharvest pathogen of table grapes, Botrytis cinerea was arrested by 40% ethanol. Dipping of grape bunches in 50, 40 or 33%, but not in 20% ethanol, prior to packaging, resulted in inhibition of berry decay that was equivalent to, or better than that achieved with SO 2, released from generator pads. Decay control was generally feasible for a cold storage period of 4–5 weeks and sometimes more. Ethanol did not impair bunch appearance, berry bloom or berry firmness and ethanol-treated berries obtained higher organoleptic scores than SO 2-treated berries.