Flavonoid and chlorogenic acid concentrations in skin of 'Jonagold' and 'Elstar' apples during and after regular and ultra low oxygen storage

Apples are important dietary sources of potentially healthy phenolics. In three successive seasons, the changes in concentrations of flavonoids and chlorogenic acid in the skin of two apple cultivars 'Jonagold' and 'Elstar' during and after regular (RS) and ultra low oxygen storage (ULO) at 1 degrees C, were quantified by reversed-phase high performance liquid chromatography (RP-HPLC) with UV-VIS detector. There were no significant differences in the concentrations of flavonoids and chlorogenic acid between fruits stored under ULO and RS conditions. During storage of both 'Jonagold' (3, 6 and 8 months) and of 'Elstar' (2, 4 and 6 months), and during 1 or 2 weeks shelf life, the concentrations of cyanidin 3-galactoside and quercetin glycosides were relatively constant, while the concentrations of catechins, phloridzin and chlorogenic acid showed only minor changes. Exposing 'Jonagold' and 'Elstar apples' to white light during shelf life following storage increased the concentration of cyanidin 3-galactoside but not any of the other flavonoid classes. An explanation for this might be that the synthesis of different flavonoid classes may have different spectral sensitivity characteristics. It is concluded that flavonoids present in apples are stable and possibly not subject to net metabolic turnover during storage and shelf life. (C) 2000 Elsevier Science B.V. All rights reserved.