Extrusion induced low-order starch matrices: Enzymic hydrolysis and structure
Bin Zhang1, Sushil Dhital1, Bernadine M Flanagan1
1Australian 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.
Carbohydrate Polymers
|October 3, 2015
Summary
Extruded high-amylose maize starch showed reduced digestion compared to cooked starch. Dense packing of amylose chains, not just crystallinity, controls enzyme resistance and digestion rate.
Area of Science:
- Food Science
- Biochemistry
- Materials Science
Background:
- Starch digestion is influenced by its structure.
- Extrusion processing can modify starch properties.
Purpose of the Study:
- To investigate the effect of extrusion on starch digestion.
- To compare digestion rates of different maize starch types after extrusion.
Main Methods:
- Extrusion of waxy, normal, and high-amylose maize starches with water.
- Enzymatic digestion assays.
- Structural analysis using NMR, XRD, and DSC.
- Molecular size analysis via size exclusion chromatography.
Main Results:
- High-amylose starch extrudates exhibited lower digestion rates and extents than those cooked in excess water.
- Structural analysis (NMR, XRD, DSC) indicated similar ordered structures between cooked and extruded high-amylose starches.
- Enzymatic resistance was significantly higher in extruded high-amylose starch, linked to longer molecular chains.
Conclusions:
- Local molecular density of amylose chain packing, rather than solely crystallinity, dictates starch digestion kinetics.
- Dense amorphous packing in extruded starches can limit enzyme binding and slow catalysis, enhancing enzyme resistance.
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