Effect of pre-treatments on the antioxidant potential of phenolic extracts from barley malt rootlets

In this study, barley malt rootlets (BMR) were subjected to five different pre-treatments (steaming (220 °C), roasting (60 °C), autoclaving (121 °C), microwaving (160-800 W, 30-120 s) and enzyme treatment). Total phenolic content (TPC) and antioxidant activity of the BMR extracts were evaluated for both free and bound phenolics. The free phenolic content for non-treated extract was 1.8 mg/g of dry weight of BMR with 17.5% of antioxidant activity. Among the pre-treatments, autoclaving exhibited the highest values for free phenolics of 3.8 mg/g of dry weight of BMR and 71.6% of antioxidant activity. Pre-treatments did not show any effect on bound phenolic content, but increased antioxidant activity. The highest %DPPH activity for bound phenolics was observed for microwave treatment (160 W, 120 s) with 49.9%. Overall, pre-treatments significantly increased the free phenolic content of BMR phenolic extracts. Additional research is necessary to understand the phenolic profile and the thermal interactions of bound phenolic extracts.