Effect of sand roasting and microwave cooking on antioxidant activity of barley

Eight different barley cultivars were roasted in sand and cooked in a microwave oven and evaluated for antioxidant activity (AOA), total phenolic content (TPC), non-enzymatic browning, polyphenol oxidase activity (PPO), total flavonoid content (TFC), reducing power and metal chelating activity. Sand roasting resulted in higher puffing index. Greater increase in yellowness of the roasted flour was brought about by microwave cooking. A significant decrease in TPC (8.5 to 49.6%) and TFC (24.5 to 53.2%) was observed after roasting. The AOA significantly increased (16.8 to 108.2%) after roasting with sand roasted barley exhibiting higher AOA. The reducing power and metal chelating activity significantly increased by up to 77.5% and 78.9%, respectively after roasting with sand roasted samples showing greater effect. The non-enzymatic browning index increased (315 to 774%) and was higher for sand roasted barley. The microwave cooking brought about a greater reduction (45.1 to 76.8%) in PPO activity.