THE CHANGES OF ETHANOLIC FERMENTATION IN BELL PEPPER FRUIT DURING INDUCTION AND RECOVERY FROM LOW OXYGEN CONDITIONS

The changes in ethanolic fermentation were studied in bell pepper fruit during induction and recovery from low O₂ conditions at storage temperature of 20°C. When exposed to different O₂ concentrations for up to 3 days, acetaldehyde (AA) and ethanol (EtOH) were only induced in the fruit exposed to 0% O₂. However, after removal from 0% O2 and transfer to air, AA and EtOH induced by 0% O₂ declined to basal levels in a linear manner for an additional 7 days. At 1% O₂, AA and EtOH levels were similar to those in fruit held in air. When exposed to different O₂ concentrations for up to 3 days, pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities only increased in the fruit exposed to 1% O₂. However, when the 1% O2 exposed fruits were transferred to air for an additional 7 days, ADH activity maintained the same level as the 1% O₂ treatment, whereas PDC gradually declined to basal levels. At 0% O₂, PDC and ADH activities were similar to those in fruit held in air. The 0% O₂ treatment resulted in a rapid accumulation of pyruvate. The pyruvate induced by 0% O₂ significantly declined to basal levels when O₂ was increased from 0 to 21% in air. At 1% O₂, pyruvate levels were similar to those in fruit held in air. The pattern of pyruvate accumulation was coincident with a doubling of AA and EtOH levels. The changes in the activities of these two fermentation enzymes did not necessarily correlate with the levels of corresponding end-products when the fruits were transferred from hypoxic to normal atmospheric conditions. Possible regulation of ethanolic fermentation during induction and recovery from low O₂ conditions is considered.