Effects of superatmospheric oxygen on strawberry fruit quality and decay

The effects of elevated O2 alone or in combination with elevated CO2 atmospheres for postharvest decay control on strawberry fruit (Fragaria×ananassa Duch.) were assessed. In vitro and in vivo growth of Botrytis cinerea Pers.:Fr. and the effects on fruit quality were determined under eight atmospheres: air, 40, 60, 80, 90 and 100 kPa O2, 40 kPa O2+15 kPa CO2 and air+15 kPa CO2. The commercially-used CO2 level of 15 kPa in air and its combination with 40 kPa O2 were most effective in suppressing mycelial growth in vitro following 7 days at 5°C under the atmospheres. However, after 14 days of treatment at 5°C, 100 kPa O2 inhibited mycelial growth more than either of the CO2 treatments. In all treatments, the growth rate increased immediately upon removal from the atmosphere, indicating that there was no residual inhibitory effect. The 100 kPa O2 treatment was also the most effective in controlling decay on the fruit during 14 days of storage. Although the quality parameters of respiration, ethylene production, firmness, soluble solids, titratable acidity and external color were only mildly affected by the superatmospheric O2 treatments, volatile content (acetaldehyde, ethanol and ethyl acetate) increased greatly. While the fruit treated with 15 kPa CO2 had the highest volatile concentrations after 14 days at 5°C, after an additional 2 days in air at 20°C, volatile concentrations in fruit treated with 100 kPa O2 equaled or surpassed those of fruit treated with CO2. The volatile concentration in fruit treated with 15 kPa CO2 generally decreased during 2 days in air, while the volatile content increased in fruit treated with high O2, with greater increases with increasing O2 level. The fruit treated with 40 kPa O2+15 kPa CO2 achieved an intermediate level between the O2 and CO2 treatments. Although the 100 kPa O2 treatment reduced decay, both in vitro and in vivo, increased production of fermentative metabolites that impart a negative organoleptic property to the fruit makes this a doubtful alternative for decay control on strawberry. © 2000 Elsevier Science B.V. All rights reserved.