Improving antioxidant activity and modifying Tartary buckwheat bran by steam explosion treatment

Steam explosion (SE) is an efficient technology to disrupt the hard structure of cereal bran and improve its biological activities. In this study, different intensities of SE were applied in Tartary buckwheat bran (TBB) to study 1) the changes of bran structures and 2) the release efficiency of polyphenols. Results illustrated SE diminished the contents of free polyphenols in TBB by 6.24–21.65%, while the bound ones were increased by 15.23–120.81%. The in vitro study demonstrated that the scavenging organic free radical DPPH· activity and oxygen radical absorption capacity (1.6 MPa for 60 s) of total polyphenols were significantly improved. Furthermore, the free quercetin contents were increased by 4–6 times and the free rutin contents were decreased by 60–75%. SE made TBB particle size changed, specific surface area increased, thermal stability enhanced, but polyphenol oxidase (PPO) activity decreased. All the results suggested that SE could enhance the antioxidant activity of TBB polyphenols through changing the constituent proportion, structure, thermal stability, and enzyme activity of bran.