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 (%), β-glucan (%) and extraction yield (%) of the fiber samples obtained from barley bran. Different enzymes including α-amylase, protease, glucoamylase, pullulanase and two types of xylanase were used in special combinations to extract β-glucan from barley bran. The three-step purification procedures with α-amylase, protease and xylanase have been proved to be efficient in increasing the β-glucan content and in removing starch, protein and pentosans from the barley bran in 4 h. The procedures also have resulted in highest β-glucan purity and lowest molecular weight of ~89% and 2 × 104 g·mol-1, respectively. While the respective lowest β-glucan purity and highest molecular weight of ~55% and 16 × 104 g·mol-1 were obtained by only α-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 β-glucan-enriched fibers, which may help to understand their function in the digestive track and industrial processes.