High CO2impact on low-temperature induced volatile esters in strawberries

Abstract

Strawberries are characterized by an intense flowery odor, which is associated with specific ester species. In this study, the effect of high CO2 atmospheres (0, 20 or 40 kPa) at 0°C on alcohol dehydrogenase (ADH) gene expression and on selected volatile esters of 'Mara des Bois' strawberries was analyzed. Acetaldehyde and ethanol concentrations, and those of hexanal and 1-hexanol were compared in strawberries stored under different high CO2 atmospheres. The abundance of each detected volatile esters varied as a function of CO2 concentration during storage. When compared with fruit at harvest, those stored at low temperature without added CO2 had a marked induction of ADH expression that was associated with the accumulation of 1-hexanol and esters typically related to fatty acid breakdown. Moreover, these fruit had the lowest concentrations of ethanol and some ethyl esters, such as ethyl butanoate. In contrast, a moderate accumulation of ethanol and specific esters associated with strawberry flavor were observed in fruit stored in a 20 kPa CO2. The shift towards ethanolic fermentation in fruit treated with 20 kPa CO2 for 3 days was associated with 1-hexanol accumulation. However, 40 kPa-treated fruit accumulated the lowest levels of octyl 3-methyl butanoate, the volatile ester with the strongest flavor in this cultivar. This reduction in conjunction with the accumulation of higher levels of acetaldehyde, ethanol and ethyl acetate could explain the negative impact on such fruits maintained in an excessively high CO2 atmosphere.