Amylolytically-resistant tapioca starch modified by combined treatment of branching enzyme and maltogenic amylase

Tapioca starch was modified using branching enzyme (BE) isolated from Bacillus subtilis 168 and Bacillus stearothermophilus maltogenic amylase (BSMA), and their molecular fine structure and susceptibility to amylolytic enzymes were investigated. By BE treatment, the molecular weight decreased from 3.1 x 10(8) to 1.7 x 10(6), the number of shorter branch chains (DIP 6-12) increased, the number of longer branch chains (DP >25) decreased, and amylose content decreased from 18.9% to 0.75%. This indicated that alpha-1,4 linkages of amylose and amylopectin were cleaved, and moiety of glycosyl residues were transferred to another amylose and amylopectin to produce branched glucan and BE-treated tapioca starch by forming alpha-1,6 branch linkages. The product was further modified with BSMA to produce highly-branched tapioca starch with 9.7% of extra branch points. When subject to digestion with human pancreatic alpha-amylase (HPA), porcine pancreatic alpha-amylase (PPA) and glucoamylase, highly-branched tapioca starch gave significantly lowered a-amylase susceptibility (7.5 times, 14.4 times and 3.9 times, respectively), compared to native tapioca starch. (C) 2008 Elsevier Ltd. All rights reserved.