Changes in condition and color during the late development of selected 'delicious' apple strains

Firmness, total soluble solids (TSS), starch concentration (starch index, SINDEX), and surface color (L*, a*, and b*) were measured for 18 'Delicious' apple strains (Malus x domestica Borkh.) produced in a replicated, randomized planting at the West Virginia Univ. Experiment Farm, Kearneysville. There was a significant difference between 1991 and 1993 for firmness, L* on the blush or outer side (BL*), Bb*, BChroma, a* (nonblush side), hue angle, and Chroma. There were significant differences between strains in firmness and chromaticities and their derivatives, but not TSS or SINDEX. All measurements changed linearly with days after full bloom (DAFB). There were large chromaticity differences between the two sides of the fruit 130 DAFB, but the nonblush side changed more than the blush side, resulting in little difference at 158 DAFB, BL*(Ba/Bb*) and L*(a*/b*) produced better separation of strains and sides than did Chroma, although the products were significantly correlated with hue angle and Chroma. The nonblush side of 'Delicious' fruits should be monitored to obtain the highest percentage of fruit in the highest grades.