Effect of toasting on physical, functional and antioxidant properties of flour from oat (Avena sativa L.) cultivars

Oat cultivars were toasted and studied for their physical properties (1000 kernel weight, bulk density, and l/b ratio). Both the control and toasted samples were milled into flour and studied for their functional (water absorption capacity, WAC; oil absorption capacity, OAC), color (L∗, a∗, b∗ values), and antioxidant (total phenolic content, TPC; antioxidant activity, AOA; metal chelating activity, MCA; and total flavonoids content, TFC) properties. Toasting resulted in significant (p < 0.05) decrease in physical parameters, hunter L∗ value, and TFC. However, it resulted in increase in WAC, OAC, hunter a∗ and b∗ values, TPC, AOA and metal chelating values. Toasting increased TPC, AOA, and MCA by 11.5-27.1%, 29.1-53.6%, 33.9-74.4%, respectively and decreased TFC by 23-40.1%. Pearson correlation coefficients (r) were also calculated to study the relationships among various properties studied. AOA exhibited a positive correlation (r = 0.931, p < 0.05) with TPC which upon toasting showed a decrease (r = 0.851, p < 0.05). TPC, AOA, MCA, and TFC of control oat cultivars varied from 1744 to 2687 μg GAE/g, 11.9% to 15.3%, 28.4% to 46.2%, and 433 to 612 μg CE/g, respectively.