Structural characterizations of waxy maize starch residue following in vitro pancreatin and amyloglucosidase synergistic hydrolysis

The objective of this work was to determine if in vitro digestion altered the molecular structure and slow digestion property of waxy maize starch. The Englyst testing on partially hydrolysis residual starches showed an increase of RDS accompanied a reduction of RS with increasing time of digestion, while SDS was almost constant. Scanning electron micrographs showed that the pattern of enzymatic hydrolysis was inside-out layer-by-layer digestion. A threefold decrease in the average molecular weight of starch components was observed after alpha-amylolysis for 120 min. There were increases in the onset temperature, peak temperature and ratio of absorbance 1047/1022 cm(-1), while the enthalpy of gelatinization, crystal structure, and crystallinity invaried. These changes suggest simultaneously enzymatic hydrolysis of both crystalline and amorphous regions of starch granule during in vitro digestion. SDS of starch residue also may consists of layered structure of amorphous and crystallite regions and located periphery of starch granules. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.