Yasuo Tatsumi

Oxygen action on respiratory processes in cucumber fruit (Cucumis sativus) stored at low temperature

Summary Respiratory processes in cucumber fruit stored in 5%, 21% (air control) and 100% O2 at 5°C were studied. Storage in 100% O2 at 5°C was most effective for suppressing the respiratory rate in cucumber fruit, the rate being lower than in fruit stored in either 5% O2 or air. Succinate dehydrogenase (SDH) activity in cucumber fruit stored in 100% O2 was lower than in other storage conditions. Only slightly different SDH activity was recorded between the control and 5% O2-treated fruit. Cucumber flesh pH in all three atmospheres increased during storage. pH showed similar increasing trends and more than one pH unit change from the initial value was recorded in control and 5% O2-treated fruit. Fruit kept in 100% O2 had a lower pH than fruit stored in 5% O2 and air. Pyruvate concentration in all three storage atmospheres increased during storage. The pyruvate concentration in 100% O2 was higher than in other storage atmospheres. The increase in pyruvate concentration in control fruit was similar to that in 5% O2 stored fruit. However, the pyruvate concentration in air-stored fruit increased sharply after day 11 and finally reached a higher level than that in 100% O2-treated fruit. Thus, the elevated O2 concentration suppressed SDH activity. This effect may be due to a reduction in fruit pH change. Consequently, reduced SDH activity in the 100% O2 treatment resulted in pyruvate accumulation which was not associated to any off-flavours. High O2 treatment has the potential to help maintain the quality of cucumber fruit. This is discussed.