Fruit quality, fermentation products, and activities of associated enzymes during elevated CO2 treatment of strawberry fruit at high and low temperatures

The effects of postharvest treatments of air and 20 kPa CO2 (in air) at 2 or 20degreesC on color, firmness, accumulations of acetaldehyde, ethanol, and ethyl acetate, activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity, and expression of an ADH gene were studied in strawberry fruit (Fragaria xananassa Duch. cv. jewel). CO2 treatment enhanced strawberry fruit firmness at 2 degreesC but not 20 degreesC, while the rate of color changes was affected by CO2 treatment at 20 degreesC but not at 2 degreesC. Temperature also affected the accumulation of acetaldehyde, ethanol and ethyl acetate in CO2-treated fruit. All three compounds accumulated in fruits at 2 degreesC. At 20 degreesC, ethanol accumulated slightly by day 6, although ethyl acetate accumulated in fruit from both atmospheres. PDC enzyme activity was higher in CO2-treated fruit than their air-treated control at 2 degreesC but not at 20 degreesC. ADH activity and ADH mRNA accumulation of the CO2-treated berries were higher than in air at 20 degreesC but not 2 degreesC. The results, overall, indicate that patterns of change among gene expression, enzyme activities, and fermentation product accumulation were not consistent.