Fermentation and ethyl esters in strawberries treated with high CO2 concentrations during low temperature storage

A short exposure of strawberries to high concentrations of CO2 helps reduce decay and control physiological disorders during low temperature storage. However, when CO2 concentrations exceed the tolerance threshold, this action may produce adverse effects related to oxidative stress, low energy charge and cellular water stress. The alterations to aroma due to the overproduction of fermentative volatiles is also a well-known detrimental effect of exposure to high CO2 concentrations, a cultivar-dependent response. Accordingly, the expression of the pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) genes, as well as the levels of ethanol, acetaldehyde and selected volatile esters were analyzed in Mara des Bois (Fragaria vesca L.) strawberries exposed to different concentrations of CO2 (0, 20 or 40 kPa) for 3 days during storage at 0?C and 95% RH. The acute induction of ADH and PDC gene expression in strawberries stored in air was accompanied by lower levels of ethanol and ethyl esters, such as ethyl butanoate and ethyl hexanoate, volatile compounds relevant to strawberry flavor. By contrast, when strawberries were exposed to high CO2 concentrations, the induction of fermentative genes does not appear to be essential for the accumulation of ethanol and acetaldehyde. The accumulation of fermentative metabolites in CO2-treated fruit was associated with the enhanced production of ethyl esters and with changes in the balance of these compounds. Specifically, the ester balance favored ethyl esters rather than methyl esters in CO2-treated fruit. In 20 kPa-treated strawberries, the marked accumulation of ethyl acetate could explain the lower levels of ethanol and acetaldehyde that accumulate relative to those in stressed 40 kPa-treated strawberries.? ? SourcesFermentation and ethyl esters in strawberries treated with high CO2 concentrations during low temperature storageCarmen Merodio1, Mar?a Blanch2, Maite S?nchez-Ballesta1, Mar?a. I Escribano11Dept. Ciencia y Tecnolog?a de Prod. Veg., Ciudad Universitaria, Jos? Antonio Novais, 10, 28040 Madrid, Spain2Paseo San Francisco de Sales 3, 8B, 28003 Madrid, SpainVIII International Postharvest Symposium, Cartagena, Spain, 21-24 June 2016 Picture:?static-imanemagazine