Antioxidant activity
3.2.1. Reducing power
The reducing powers of MEs from fresh, FD, and
AD tomatoes along with a-tocopherol and BHA are
shown in Fig. 5. In general, the reducing powers of all
the tomato samples were raised with the increase of
MEs concentration while in lower concentration and
reached a level-off in higher concentration. At concentration
up to 8 mg/mL, the reducing powers in all tomato
samples were higher than that of a-tocopherol and
BHA. Meanwhile, both FD-ITH and FD-SN tomatoes
exhibited excellent reducing powers. The two varieties
of fresh tomatoes came next. Both AD-ITH and
AD-SN showed the lowest reducing powers while the
concentrations up to 12 mg/mL. The reducing power
of MEs in various processed products might be due to
their hydrogen-donating ability as described by Shimada
et al. (1992). Accordingly, the MEs from FD-SN tomato
would contain the highest amount of reductone, which
could react with free radicals to stabilize and terminate
radical chain reactions