Although PPO has poor affinity for these pigments its action is
strongly enhanced by the presence of phenols. The
latter induces high rates of o-quinone synthesis and
acts as activators of anthocyanin degradation . POD may also be
involved in the degradation of anthocyanins . Its activity may be limited by the
availability of H2O2in situ. Browning may also result
from the direct action of anthocyanase on anthocyanins.
Anthocyanidins thus formed are spontaneously damaged at high pH (above 4.7 in vivo) ,
and their degradation products are potential substrates
for PPO (Zhang et al., 2001).