title: Extrusion induced low-order starch matrices: Enzymic hydrolysis and structure.
abstract: Waxy, normal and highwaymen maize starches were extruded with water as sole plasticizer to achieve low-order starch matrices. Of the three starches, we found that only high-amylose extrudate showed lower digestion rate/extent than starches cooked in excess water. The ordered structure of high-amylose starches in cooked and extruded forms was similar, as judged by NMR, XRD and DSC techniques, but enzyme resistance was much greater for extruded forms. Size exclusion chromatography suggested that longer chains were involved in enzyme resistance. We propose that the local molecular density of packing of amylose chains can control the digestion kinetics rather than just crystallinity, with the principle being that density sufficient to either prevent/limit binding and/or slow down catalysis can be achieved by dense amorphous packing.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia. Electronic address: binzhang@purdue.edu.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia. Electronic address: s.dhital@uq.edu.au.
authors.forename: Sushil
authors.initials: S
authors.lastname: Dhital
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia. Electronic address: b.flanagan@uq.edu.au.
authors.forename: Bernadine M
authors.initials: BM
authors.lastname: Flanagan
authors.affiliation: School of Chemical Engineering, and Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia. Electronic address: p.luckman@uq.edu.au.
authors.forename: Paul
authors.initials: P
authors.lastname: Luckman
authors.affiliation: School of Chemical Engineering, and Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia. Electronic address: p.halley@uq.edu.au.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Halley
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia. Electronic address: m.gidley@uq.edu.au.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gidley
mesh_terms: D000818:Animals; D006868:Hydrolysis; D007700:Kinetics; D013213:Starch / Q000737:chemistry* / Q000378:metabolism*; D013552:Swine; D000516:alpha-Amylases / Q000378:metabolism*
chemical_list: D013213:Starch; D000516:alpha-Amylases
keywords: Enzyme-resistant starch; Extrusion; High-amylose starch; In vitro digestion; Local molecular density