Enzyme‐synthesized highly branched maltodextrins have slow glucogenesis at the mucosal α‐glucosidase level and are slowly digestible in vivo

Abstract

For starch digestion, α‐amylase first hydrolyzes starch to produce α‐limit dextrins, followed by complete hydrolysis to glucose by the mucosal α‐glucosidases in the small intestine. It is known that α‐1,6 linkages in starch are hydrolyzed more slowly than α‐1,4 linkages. Here, to create designed slowly digestible carbohydrates, the structure of waxy corn starch (WCS) was modified using a branching enzyme alone (BE) and an in combination with β‐amylase (BA) to increase further the α‐1,6 branching ratio. Enzyme‐modified products (BE‐WCS and BEBA‐WCS) had increased percentage of α‐1,6 linkages (WCS: 5.3%, BE‐WCS: 7.1%, and BEBA‐WCS: 12.9%). Hydrolysis by human pancreatic α‐amylase resulted in an increase in the amount of branched α‐limit dextrin from 26.8% (WCS) to 56.8% (BEBA‐WCS). The α‐amylolyzed samples were hydrolyzed by the individual α‐glucosidases and glucogenesis decreased as the branching ratio increased. This result showed that hydrolysis rate of the mucosal α‐glucosidases was limited by the amount of branched α‐limit dextrin. When samples were gavaged to rats, the level of postprandial blood glucose at 60 min from BEBA‐WCS was significantly higher than for WCS or BE‐WCS. Thus, highly branched glucan structures modified by BE and BA had a comparably slow digesting property both in vitro and in vivo. Such highly branched α‐glucans show promise as a food ingredient to control postprandial glucose levels.Grant Funding Source: USDA AFRI competitive grant program