Accumulation of anthocyanins and quercetin glycosides in 'Gala' and 'RoyalGala' apple fruit skin with UV-B-Visible irradiation: modifying effects offruit maturity, fruit side, and temperature

We measured the accumulation of the anthocyanins and quercetin glycosides, after irradiation with UV-B-Visible light, in the skin of apple fruit (Malu s domestica Borkh.), 'Gala' and 'Royal Gala', at two temperatures, 10 and 2 0 degreesC for five harvests up to 2 weeks after the start of the commercia l harvest. The response to irradiation was compared between sides of the fr uit that were outer facing (exposed) and inner facing (shaded) when on the tree. The tree-shaded side of the fruit had a much greater potential to acc umulate anthocyanins and quercetin glycosides than the tree-exposed side. T his potential of the detached fruit to accumulate anthocyanin in the skin w ith UV-B-Visible radiation was decreased by fruit maturity at the last harv est. Lower temperature of 10 degreesC prevented the accumulation of anthocy anins and quercetin glycosides compared with 20 degreesC during irradiation with UV-B-Visible light. 'Royal Gala', the red sport of 'Gala', accumulate d anthocyanins, but not quercetin glycosides, to higher concentrations than 'Gala'. The results show that maturity, the fruit skin's previous exposure to light and temperature are major modifying factors in the accumulation o f anthocyanins by 'Gala' and its sport 'Royal Gala'. (C) 2001 Elsevier Scie nce B.V. All rights reserved.