As a result of enzymatic oxidation, a sharp decrease in the concentration
of phenolic compounds was observed in the control lettuce.
Loss of individual phenolic compounds identified in lettuce
was expressed in terms of the first order degradation rate constant
(k). The results are summarised in Table 1. The results are in agreement
with the results obtained by others (Nourian, Ramaswamy, &
Kushalappa, 2003). Phenolic compounds and PPO originally exist
separately in different organelles in plant cells. When the plant is
damaged, phenolic compounds and PPO come into contact and react
and parts of the phenolic compounds are isomerized (Rigal
et al., 2000).