Ethanol vapor is efficient for reduction of astringency compounds in cashew apple

Cashew nut is known and appreciated worldwide, but the cashew apple has a low consumption, which is related to its high astringency. Condensed tannins or proanthocyanidins are the polyphenols responsible for this gustatory sensation. The use of ethanol as a deastringency agent is not the most used technique for astringency removal, but it has low cost, simplified application and high efficiency. This study aimed to verify whether ethanol vapor is able to penetrate cashew apples and reduce their astringency without causing fermentation, as well as to determine the best dose and exposure time of cashews to ethanol. Two experiments were conducted: in the first, the exposure time of the cashews to ethanol was 12 h and, in the second, it was 24 h. In both experiments, cashew apples early dwarf clone CCP-76 was used, the tested doses were 0.0 (control), 1.75, 3.50, 7.00, and 14.00 mL kg−1 of fruit, and the storage period was 16 d, in a cold chamber at 5 °C and 90% RH. Anatomical analyses showed the presence of secretory canals distributed in the parenchyma and stomata in the epidermis, indicating that the ethanol vapor was able to penetrate the cashew apples. Chromatographic analyses performed during treatment application showed that the ethanol vapor was absorbed by the pseudofruit and that the required doses were correct. The contents of ethanol, acetaldehyde, proanthocyanidins and total polyphenols of the cashew apple pulp were influenced by the dose, but not by the exposure time to ethanol, with 3.50 mL kg−1 being enough to reduce the tannins to the lowest levels. The two highest doses of ethanol resulted in cashew apple fermentation, skin depigmentation, which altered its color, and increased weight loss. Firmness and decay incidence were not altered. Thus, ethanol application at a dose of 3.5 mL kg−1 of fruit for 12 h of exposure time reduced the astringency compounds of the cashew apples without impairing their postharvest quality.