For determination and quantification, the quercetin derivatives
quercetin dihydrate, quercetin-3-O-glucoside, quercetin-
3-O-galactoside, quercetin-3-O-arabinopyranoside, and
quercetin-3-O-rhamnoside were used as standards and obtained
from Roth (Karlsruhe, Germany). Apples (Malus domestica Borkh.
cultivar ‘Braeburn’) were purchased from a local producer and
stored at ambient temperature (20 C) until experimental use.
The bulk density of whole apple fruits measured by water
displacement was 0.913 0.013 g/cm3 (n ¼ 24). The native
Braeburn slices contained 87.6 0.5 g/100 g moisture, which
equals a water activity of 0.97. The used Braeburn apples had a
fruit firmness of 8.2 1.1 kg/cm2 and the soluble solids
(11.9 1.0 Brix).