Effect of sand roasting on beta glucan extractability, physicochemical and antioxidant properties of oats

The antioxidant properties, damaged starch, beta glucan extractability and physicochemical properties of ten different oat cultivars were studied after sand roasting at 280 °C for 15 s. The groat content within the cultivars varied from 6.59 to 7.76 g/10 g oats. Roasting lowered the length/breadth ratio and bulk density and resulted in puffing of the groats. Color characteristics a∗ indicating redness and b∗ indicating yellowness and nonenzymatic browning index significantly (p < 0.05) increased upon roasting. The total phenolic (μg FAE/g) and flavonoid content (μg/g) decreased significantly by 11.4-50.2% and 22.7-49.9%, respectively. An increase in reducing power (μmol AAE/g) ranging from 1.1 to 37.6% and metal chelating activity ranging from 13.2 to 180.2% was observed in the roasted groats. The DPPH radical scavenging activity in the roasted groats increased by 4.6-73.0%. The peak viscosity of the roasted groat flour decreased by 9.1-51.1% while the final viscosity decreased by 15.4-57.5%. The damaged starch content in the groats increased after roasting and the increase ranged from 72 to 82%. Roasting significantly increased the extractable beta glucan content in the groats by 9.8-61.1%. It was concluded that roasting significantly affects the physicochemical and pasting behavior of groats and increases the availability of phytochemicals like beta glucan and the total antioxidant activity.

► Roasting increased the damaged starch and extractable beta glucan content. ► The TPC and TFC decreased whereas reducing power increased. ► The DPPH radical scavenging activity in the roasted groats increased significantly.