Peach ripening: Segregation at harvest and postharvest flesh softening

The peach melting flesh cultivars 'Ryan Sun' and 'Sweet September' and the non-melting, 'Kakamas' were harvested 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), ground skin hue angle (h degrees) and chroma (C*), the absorbance difference at 670 nm and, 720 nm index (I-AD), and the 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 degrees of the, ground color and the I-AD are maturity indicators closely associated with ripeness and particularly with, flesh firmness, the texture parameters and their relationship to h degrees and I-AD were examined. The visual, assessment of the ground color was validated as the criterion for sorting the ripeness levels in peaches, as confirmed by h degrees and I-AD. Fruit firmness assessed with the needle and that with the 7.9 mm plunger, were highly correlated with each other and with the h degrees and I-AD, whereas the compression strength, exhibited less correlation with the optical properties of the skin. The non-melting 'Kakamas' showed, the poorest correlation between texture and h degrees and I-AD. Comparing both optical properties, the I-AD, showed a higher correlation with texture features than the h degrees. In a second experiment, fruit from the M3 ripeness class was maintained in a ripening chamber (20 degrees 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 variance of the texture, components and the optical properties of the skin. PC1 (67.2%) was defined positively by the texture, parameters and I-AD. The h degrees of the ground color was negatively related to all texture parameters, and, I-AD. PC2 (17.8%) was associated positively with the juice content, and this parameter proved to be, independent of all others. (C) 2013 Elsevier B.V. All rights reserved.