Peach ripening: Segregation at harvest and postharvest flesh softening

Abstract

tThe 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 (h◦) 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 h◦of the, ground color and the IADare maturity indicators closely associated with ripeness and particularly with, flesh firmness, the textureparameters and their relationship to h◦and IADwere examined. The visual, assessment of the groundcolor was validated as the criterion for sorting the ripeness levels in peaches, as confirmed by h◦and IAD.Fruit firmness assessed with the needle and that with the 7.9 mm plunger, were highly correlated witheach other and with the h◦and IAD, whereas the compression strength, exhibited less correlation withthe optical properties of the skin. The non-melting ‘Kakamas’ showed, the poorest correlation betweentexture and h◦and IAD. Comparing both optical properties, the IAD, showed a higher correlation withtexture features than the h◦. In a second experiment, fruit from the M3 ripeness class was maintained ina ripening chamber (20◦C, 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 h◦of 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.