A two-stage modification method using 1,4-α-glucan branching enzyme lowers the in vitro digestibility of corn starch.

Samples of granular corn starch were treated with 1,4-α-glucan branching enzyme (GBE) for 20 h using three different methods. These GBE modification methods all increased glycosidic linkage ratio, cyclic glucan content, and proportion of short chains while reducing weight mean molecular weight. The in vitro digestion rates of the modified starches were suppressed. Among these methods, a novel two-stage modification method comprising a 10-h GBE treatment, gelatinization, and a second 10-h GBE treatment, produced samples with the lowest in vitro digestibility. The rapidly digestible starch content was 34.2% lower than that of the control and 18.0% lower than that of the product of one-stage modification with the same duration. Fine structure characterization showed that more cluster structures were proved during the two-stage modification. This two-stage method suppressed the digestibility of corn starch and increased the substrate concentration, showing great potential for the industrial processing of slowly-digestible starchy foods.