CHANGES IN QUALITY AND MATURITY OF LATE SEASON NECTARINES (cvs. JULY RED AND AUGUST RED) DURING MATURATION AND RIPENING

The objectives were to characterize the quality and maturity changes of nectarine (Prunus persica var. Nectarina) fruit cvs. July Red and August Red during maturation and ripening, and to identify harvest maturity indices relating the different variables, by means of Pearson correlation coefficients.
After fruit set, 400 similar fruits were tagged in order to follow maturation and ripening on the tree. During harvest, 48 fruits were randomly harvested every 3-6 days. The ethylene evolution rate (EER) at 20°C, the fresh weight, the peel ground and cover colours (L*, a*, b*, C* and hue value) were measured in all 48 fruits. Flesh colour, firmness at several points on the fruits, soluble solids (SS), pH, titratable acidity (TA) and SS/TA ratio were measured in only 24 fruits, and the remaining fruits were held at 20°C for up to 7 days, after which the same parameters were measured again. Significant changes occurred during maturation of both cultivars, in fruit firmness, peel ground colour (a* and hue value), TA, SS/TA and fruit size. In July Red there were also significant changes in EER and cover colour. Correlation coefficients higher than 0.7 were found between log EER and fruit firmness for both cultivars, and between log EER and a*, and between EER and the SS/TA ratio, for July Red. Fruit softening varied according to the point of measurement on the fruit. No harvest indices could be identified for either cultivar.