As shown in Fig. 3, the a-amylase treatment significantly increased (p < 0.01) the DPPH radical scavenging activity of oat flour in a time-dependent manner with a maximum value at 60 min. The heating-only treatment showed an overall decrease(p < 0.01) in DPPH radical scavenging activity with treatment duration. The difference between a-amylase-treated and heatingonly samples was significant (p < 0.01). The interaction between treatment method and treating time also showed significant influence on the DPPH values of the extracts from different treated oat pastes (p < 0.05). In addition, there was a significant positive correlation between activity in the DPPH assay and the phenols content (r ¼ 0.97, p < 0.05). However, the antioxidant activity as
determined by the DPPH assay was not consistent with that determined by the ABTS assay (r ¼ 0.08). This trend was also reported by Verma et al. (2009).