Thermal preservation is believed to be responsible for a depletion
of naturally occurring antioxidants in food. The overall antioxidant
properties of foods may be affected by processing in several ways,
including losses of naturally occurring compounds, improvement
of their antioxidant properties, as well as formation of novel compounds
by Maillard or other reactions that affect antioxidant activity
(Nicoli, Anese, & Parpinel, 1999). The main causes of lycopene degradation
during thermal processing of tomatoes are oxidation and
isomerisation (Shi & Le Maguer, 2000). Vitamin C is also high susceptible
to oxidation in the presence of oxygen (Davey et al., 2000).