This might be attributed to the increased
extractability of phenolic compounds due to the
disruption of plant cell walls during high heat
treatment, which might cause phenolic compounds
to be released more easily than in raw materials
and with lower heat treatment. These results were
consistent with those of Scalzo et al. (2004), who
reported that thermal treatment generally induced
an increase in the main phenolic substances of
orange juice, such as anthocyanins and total
cinnamates,and those of Choi et al. (2006), who reported that heat treatment of Shiitake mushrooms
increased the overall content of free polyphenolic
and flavonoid compounds. They suggested that
bound polyphenolic and flavonoid compounds
could be liberated by heat treatment. Kim et al.
(2006) also reported an increase in the TPC in
heated grape seed due to the liberated phenolic
compounds.