Extrusion and fungal fermentation change the profile and antioxidant activity of free and bound phenolics in rice bran together with the phenolic bioaccessibility

• Published in: Food science & technology 2019-11, Vol.115, p.108461, Article 108461
• Main Authors: Chen, Yanxia, Ma, Yongxuan, Dong, Lihong, Jia, Xuchao, Liu, Lei, Huang, Fei, Chi, Jianwei, Xiao, Juan, Zhang, Mingwei, Zhang, Ruifen
• Format: Article
• Language: English
• Subjects: Antioxidant activity; Defatted rice bran; Extrusion; Fermentation; Phenolic bioaccessibility
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2019.108461

The effects of extrusion and fermentation on the free and bound phenolic distribution in grains and related products remain controversial. The phenolic bioaccessibility have not been comprehensively studied. Therefore, the effects of extrusion and fermentation on phenolic profiles and bioaccessibility, together with the antioxidant activity in defatted rice bran (DRB) were investigated in this study. Our results revealed extrusion and fermentation not only facilitate the release of phenolics, improve the extractability of bound phenolics in DRB. The free, bound and total phenolic content increased by 23.0%, 50.7% and 36.3% after extrusion, and by 99.4%, 40% and 71.6% after fermentation, respectively. Extrusion and fermentation changed the content and distribution of 8 detected phenolic compounds but not composition in DRB. Fermentation enhanced ORAC and CAA antioxidant activity with 1.8 and 4.1 folds increases, respectively, while extrusion had no effect on CAA. Bioaccessibile phenolics increased by 40.5 and 64.4% in extruded and fermented DRB after in vitro digestion compared with raw DRB, respectively. Scanning electron microscope analysis showed extrusion and fermentation changed the compact microstructure of DRB to loose and porous structure. Our research indicates fermented and extruded DRB (especially the former) represent potentially promising materials for developing health foods and nutraceuticals. •Extrusion & fermentation increased bound phenolics in DRB by improving extractability.•Extrusion & fermentation changed phenolic profile and distribution differently in DRB.•Fermentation but not extrusion increased the CAA activity of phenolics in DRB.•Fermentation provided more increased bioaccessible phenolics from DRB than extrusion.