None of the combinations of chitosan
with oleoresins enhanced the reduction of PPO activity from
butter and romaine lettuce extracts. The combination of chitosan
and rosemary oleoresin was less effective in the reduction of PPO
activity from butter lettuce than chitosan or rosemary oleoresins
by themselves. Possible interactions between functional chemical
groups of rosemary and chitosan could account for the loss of
antioxidant properties (Pranoto et al., 2005). Generally speaking,
when the film-forming solutions were added to the oleoresins, the
latter lost, or at their best, retained their potential to reduce POD
and PPO activities.