Preparation of resistant glucan by high pressure processing (HPP) and enzymatic methods increases indigestibility

This study describes a new method for producing high-quality resistant glucan by characterizing the structural mechanism of indigestibility. The structures and properties of resistant glucans were characterized before and after in vitro simulated digestion. The results demonstrated that high-pressure processing (HPP) led to the complete disappearance of crystal peaks and increased the efficiency of the two enzymes (α-amylase and transglucosidase). Moreover, α-1,6 and β-linkages were abundant in the connecting parts of the long and branching chains in the resulting resistant glucans, thus hindering the ability of digestive enzymes to hydrolyze short chains with a degree of polymerization (DP) ≤ 6. In addition, transglucosidase activity led to a higher proportion of short chains (DP 3-6), further promoting indigestibility. We demonstrated that, without rectification and decolorization, the dietary fiber content was >75 %, and the degree of branching increased to 50.9 %, indicating higher indigestibility than that resistant glucans produced by traditional methods.