Influence of harvest date within the season and cold storage on cherimoya fruit ripening.

Cherimoya ripening with and without prior storage at 8 degrees C was studied in fruit harvested on early- (EH), mid- (MH), and late-season (LH) dates. Most of the differences in the ripening behavior were observed between EH cherimoyas and fruit from the other two harvest dates. During ripening of nonstored fruit, the increases in ethylene production and respiration rates and in soluble sugars and organic acids contents were faster in EH than in the other fruits (which ripened 1 day later). These differences could be due to variations in the physiological stage at harvest as a result of the different heat units (degree/month) accumulated in the last month of fruit development. During ripening of cold-stored fruit the differences in the time to the onset of the increase in ethylene production and in the accumulation of malic and citric acid were minimized, especially after longer storage times, and the relationship of harvest date with the increases in respiration rate was lost. Glucose and fructose accumulation was reduced by prior cold storage, especially after longer storage duration and in MH and LH fruit, but sucrose hydrolysis was almost complete, as in nonstored fruit. It is suggested that glucose and fructose accumulation is more sensitive to low temperature than sucrose metabolism and that this differential sensitivity is more marked in MH and LH cherimoyas. The time to ripen was inversely related to prior cold storage duration and was dependent on harvest date: the later the harvest date, the longer storage time it took to shorten subsequent ripening.