ETHANOLIC METABOLISM IN CHERIMOYA FRUIT DURING STORAGE AT AMBIENT ANDUNDER HIGH CO2 ATMOSPHERES

Cherimoya fruits (Annona cherimola, Mill.) were kept in 20% O-2 + 20% CO2 for UP to 3 d at 20 degrees C and then transferred to air to study the effect of high CO2 levels on fermentation enzymes, ethanol and ac ethaldehyde content and ripening evolution. Ethanol and acetaldehyde c ontent increased during ripening in air mainly associated with the fir st respiration peak. At the end of the short-term high CO2 treatment, cherimoya fruit had a lower aerobic respiration rate while concentrati ons of acethaldehyde and ethanol were greatly increased compared with those of air-control fruit. The activation of fermentation pathway by high CO2 atmosphere is mainly due to an enhancement in pyruvate decarb oxylase (PDC) activity. High CO2 treatment prevented the ripening proc ess but, after transfer to air a decrease in fermentation metabolism w as recorded and fruit was able to ripen, showing a typical decrease in tissue pH.