Molecular rearrangement of starch during in vitro digestion: toward a better understanding of enzyme resistant starch formation in processed starches

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dc.contributor.authorLopez-Rubio, Aen_AU
dc.contributor.authorFlanagan, BMen_AU
dc.contributor.authorShrestha, AKen_AU
dc.contributor.authorGidley, MJen_AU
dc.contributor.authorGilbert, EPen_AU
dc.date.accessioned2009-10-07T05:59:34Zen_AU
dc.date.accessioned2010-04-30T05:07:01Zen_AU
dc.date.available2009-10-07T05:59:34Zen_AU
dc.date.available2010-04-30T05:07:01Zen_AU
dc.date.issued2008-07en_AU
dc.date.statistics2008-07en_AU
dc.description.abstractResistant starch (RS) is defined as the fraction of starch that escapes digestion in the small intestine, serving as a fermentation substrate for beneficial colonic bacteria. Several studies have been focused on the description of the RS fractions from different starch varieties, but little attention has been paid to the digestion process itself that, from the present work, seems to play a key role in the generation of enzyme-RS (ERS), as determined in vitro. High-amylose starch samples, extruded at two different processing conditions, have been characterized at different stages of in vitro digestion using scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), infrared spectroscopy (FF-IR), solid state C-13 NMR spectroscopy, and X-ray diffraction (XRD). Control samples kept for 18 h in the digestion solution without starch hydrolyzing enzymes (alpha-amylase and amyloglucosidase) were used for comparison purposes. An increase in molecular order was favored by the hydrolytic action of the enzymes, reflected in an increase in double helical order observed by NMR, higher crystallinity measured by XRD, and corresponding changes in FT-IR spectra. An increase in the intensity of the scattering objects was also observed by SAXS as a function of digestion. SAXS from the dry ERS fractions reveals the 001 reflection of crystallites formed during the digestion process, corresponding to a characteristic dimension of the resistant crystalline fraction of similar to 5 nm. The changes found suggest that enzyme resistant starch does not refer to a specific structure present in predigested starches, but may in fact be formed during the digestion process through the rearrangement of amylose chains into enzyme-resistant structures of higher crystallinity. Therefore, the resistance to enzyme digestion of a specific processed starch is the result of a competition between the kinetics of enzyme hydrolysis and the kinetics of amylose retrogradation. © 2008, American Chemical Societyen_AU
dc.identifier.citationLopez-Rubio, A., Flanagan, B. M., Shrestha, A. K., Gidley, M. J., & Gilbert, E. P. (2008). Molecular rearrangement of starch during in vitro digestion: toward a better understanding of enzyme resistant starch formation in processed starches. Biomacromolecules, 9(7), 1951-1958. doi:10.1021/bm800213hen_AU
dc.identifier.govdoc1448en_AU
dc.identifier.issn1525-7797en_AU
dc.identifier.issue7en_AU
dc.identifier.journaltitleBiomacromoleculesen_AU
dc.identifier.pagination1951-1958en_AU
dc.identifier.urihttp://dx.doi.org/10.1021/bm800213hen_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/1952en_AU
dc.identifier.volume9en_AU
dc.language.isoenen_AU
dc.publisherAmerican Chemical Societyen_AU
dc.subjectStarchen_AU
dc.subjectDigestionen_AU
dc.subjectIn vitroen_AU
dc.subjectEnzymesen_AU
dc.subjectScanning electron microscopyen_AU
dc.subjectSmall angle scatteringen_AU
dc.titleMolecular rearrangement of starch during in vitro digestion: toward a better understanding of enzyme resistant starch formation in processed starchesen_AU
dc.typeJournal Articleen_AU
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