Effect of different enzymatic extractions on molecular weight distribution, rheological and microstructural properties of barley bran β-glucan

The aim of this study was to investigate the effects of different enzymatic extraction procedures on molecular weight distribution, rheological behavior, microstructural properties, compositional factors including ash (%), starch (%), pentosans (%), beta-glucan (%) and extraction yield (%) of the fiber samples obtained from barley bran. Different enzymes including alpha-amylase, protease, glucoamylase, pullulanase and two types of xylanase were used in special combinations to extract beta-glucan from barley bran. The three-step purification procedures with alpha-amylase, protease and xylanase have been proved to be efficient in increasing the beta-glucan content and in removing starch, protein and pentosans from the barley bran in 4 h. The procedures also have resulted in highest beta-glucan purity and lowest molecular weight of similar to 89% and 2 x 10(4) g.mol(-1), respectively. While the respective lowest beta-glucan purity and highest molecular weight of similar to 55% and 16 x 10(4) g.mol(-1) were obtained by only alpha-amylase treatment in 1.5 h. Regardless of different purity, extraction yield and composition, the results of this study showed that how enzymatic extractions affect molecular-rheological relationship of the beta-glucan-enriched fibers, which may help to understand their function in the digestive track and industrial processes. (C) 2018 Elsevier B.V. All rights reserved.