Chlorogenic acid was found to be the major phenolic
compound in blueberries by Kader et al. (1996) and Zheng and
Wang (2003), and the activity of polyphenoloxidase was
considered to be high between pH 3 and 5 by Kader et al.
(1998). Since the pH value of the blueberries studied here was
2.92 (data not yet published), it is possible that most of the
degradation of the anthocyanins resulted from cyanidin and
delphinidin as a consequence of oxidation reactions. A similar
reaction was found for blueberry juice as a result of the action of
the enzyme peroxidase in the presence of chlorogenic acid and
hydrogen peroxide, pelargonidin-3-glucoside degrading less
than cyanidin-3-glucoside (Kader et al., 2002).