Peach ripening: Segregation at harvest and postharvest flesh softening

The peach melting flesh cultivars 'Ryan Sun' and 'Sweet September' and the non-melting, 'Kakamas' wereharvested according to their visually assessed ground color and divided into four, ripeness classes (M1,M2, M3, and M4). The following aspects were determined: fruit mass, soluble, solids content (SSC), groundskin hue angle (ho) and chroma (C*), the absorbance difference at 670 nm and, 720 nm index (IAD), andthe texture (fruit firmness measured with a needle, flesh firmness measured, with a 7.9 mm plunger,and uniaxial compression strength). Considering that in peaches, the hoof the, ground color and the IADare maturity indicators closely associated with ripeness and particularly with, flesh firmness, the textureparameters and their relationship to hoand IADwere examined. The visual, assessment of the groundcolor was validated as the criterion for sorting the ripeness levels in peaches, as confirmed by hoand IAD.Fruit firmness assessed with the needle and that with the 7.9 mm plunger, were highly correlated witheach other and with the hoand IAD, whereas the compression strength, exhibited less correlation withthe optical properties of the skin. The non-melting 'Kakamas' showed, the poorest correlation betweentexture and hoand IAD. Comparing both optical properties, the IAD, showed a higher correlation withtexture features than the ho. In a second experiment, fruit from the M3 ripeness class was maintained ina ripening chamber (20oC, and 80% RH) until the flesh was softened for consumption. During postharvest,the first two principal, components of a principal component analysis explained 85% of the total varianceof the texture, components and the optical properties of the skin. PC1 (67.2%) was defined positively by thetexture, parameters and IAD. The hoof the ground color was negatively related to all texture parameters,and, IAD. PC2 (17.8%) was associated positively with the juice content, and this parameter proved to be,independent of all others.