Tissue softening may also result
from physicochemical reactions that take place in the cell wall
matrix such as ß-elimination of pectin (Sila, Smout, Elliot, Loey, &
Hendrickx, 2006). At the lower temperatures of 30 and 50 C tissue
softening, starch gelatinization, and PPO inactivation was minor
and resulted in limited to moderate enhancement of anthocyanin
extraction. Following the pre-heating treatments, PSP were extracted
in acidified water at 70 C, a temperature that would reduce the
impact of oxidase enzymes during maceration and holding, and to
minimize starch gelatinization in all but the 90 C pre-heating treatment,
so that the majority of native starch could easily be removed
by precipitation. It is co-incidental that both thermal denaturation
of PPO and the lower end of the starch gelatinization temperature
range for PSP are both near 70 C