Effect of steam, microwave, and hot‐air drying on antioxidant capacity and in vitro digestion properties of polyphenols in oat bran

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In oats, polyphenols are mainly present in the outer layer of the oat grain in a bound state. This study addressed the limited knowledge regarding the antioxidant activity and in vitro digestion properties of oat brans under three drying methods: steam, microwave, and hot-air drying. The total polyphenol content, antioxidant activity (OH, DPPH, ABTS, and T-AOC), and in vitro digestion properties of 60- and 80-mesh oat brans were determined. The steaming-treated oat brans exhibited higher total polyphenol content, DPPH scavenging rate, and antioxidant capacity than those treated with the other two methods. Moreover, the·OH scavenging capacity and ABTS radical scavenging rate of steaming-treated oat brans were not significantly different from those of the oat brans treated with the other two methods (p < .05). The three investigated drying methods can increase the in vitro bioavailability of the polyphenol content and antioxidants in oat brans. Novelty impact statement Steaming, microwaving, and hot-air drying deeply modified the total phenol content and antioxidants in oat bran. Steaming resulted in the greatest increase in the in vitro bioavailability of polyphenols and their antioxidant activity.