Overall quality, phenolic compounds, and volatile profile of ‘BRS Isis’ seedless table grapes after long-term storage: Effect of ethanol and high CO2

Abstract

This study aimed to evaluate the effect of different ethanol and CO2 concentrations on the quality maintenance of ‘BRS Isis’ table grapes, as alternatives to sulfur dioxide during storage. The following storage conditions were evaluated: [1] control; [2] sulfur dioxide (SO2); [3] 1,125 ppm ethanol; [4] 2,250 ppm ethanol; [5] 10 kPa CO2 and; [6] 15 kPa CO2. ‘BRS Isis’ grapes were stored in vented polyethylene clamshells, allocated inside experimental chambers during 60 and 90 days, at 0.5°C, followed by four days shelf life at 20°C. Then, physicochemical quality, phenolic, and volatile profile were determined. Storage with 2,250 ppm ethanol and 15 kPa CO2 showed similar effectiveness to SO2 in controlling berry shattering and decay. SO2 prevented the rachis browning but caused berries bleaching. Both high CO2 concentrations and the treatment with 2,250 ppm ethanol resulted in higher berry firmness, however, ethanol increased cracking incidence. Ethanol increased alcohols, aldehydes, and especially esters concentration, however, resulted in acetaldehyde and ethyl acetate accumulation, which may be related to unpleasant aromas in the grapes. The high CO2 was efficient on the quality maintenance of the stored grapes, resulting in higher phenolic compounds, flavonoids, and anthocyanins concentrations, in addition to the volatile compounds hexanal and (E)-2-hexenal, which are related to grapes freshness. Therefore, ethanol, and especially high CO2, are promising alternatives to SO2 in maintaining the ‘BRS Isis’ table grape quality during prolonged storage.