Solutions of pigmented proanthocyanidins
(5 g/L) were prepared in aqueous 0.1 N HCl and
in 50% aqueous acetone or methanol (0.1 N HCl). Spectra were
recorded as soon as practically possible to eliminate potential
interference by formation of anthocyanidin degradation product.
Aqueous proanthocyanidin solutions were also exposed to
potassium metabisulfite as previously described (21). All
spectra were obtained using a Cary 100 spectrophotometer
(Varian, Palo Alto, CA).