Removal of bound polyphenols and its effect on antioxidant and prebiotics properties of carrot dietary fiber

The present work was designed to investigate the effect of bound polyphenols on antioxidant and prebiotics properties of carrot dietary fiber (CDF). The polyphenols were removed from CDF by alkaline extraction to obtain dephenolized dietary fiber (CDF-DF). The optimized conditions of extracting polyphenols from CDF were solid-liquid ratio of 1:8.5, the treat temperature of α-amylase 66 °C, the addition of protease of 0.2% and the treat temperature of amyloglucosidase 60 °C, respectively. The FT-IR spectroscopy illustrated that the major functional group of CDF-DF and CDF shared most of the key features, despite changes in the amplitude of some functional groups. Scanning electron microscopy (SEM) was further performed demonstrating no significant structure differences between CDF-DF and CDF. Moreover, the antioxidant properties, including superoxide anion radical, hydroxyl radical and DPPH radical scavenging activity, of CDF-DF were significantly lower than that of CDF. In addition, CDF was more conducive for the growth of Lactobacillus rhamnosus as compared with the CDF-DF. In summary, the above results concluded that there was no significant change of the dietary fiber after removal of bound polyphenols, and the bound polyphenols contributed significantly to the antioxidant and prebiotics properties of dietary fiber from carrot.