Effects of processing high amylose maize starches under controlled conditions on structural organisation and amylase digestibility

• Published in: Carbohydrate polymers 2009-01, Vol.75 (2), p.236-245
• Main Authors: Htoon, A., Shrestha, A.K., Flanagan, B.M., Lopez-Rubio, A., Bird, A.R., Gilbert, E.P., Gidley, M.J.
• Format: Article
• Language: English
• Subjects: Amylose; Applied sciences; Crystallinity; Exact sciences and technology; Extrusion; Maize starch; Natural polymers; Physicochemistry of polymers; Resistant starch; Spectroscopy; Starch and polysaccharides; Zea mays
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2008.06.016

The amylase digestibility of high-amylose maize starches has been compared before and after thermo-mechanical processing. Starches were analysed for enzyme-resistant starch yield, apparent amylose content, crystallinity (X-ray diffraction), and molecular order (NMR and FTIR), both before and after treatment with α-amylase. All samples had significant (>10%) enzyme-resistant starch levels irrespective of the type and extent of thermal or enzymic processing. Molecular or crystalline order was not a pre-requisite for enzyme resistance. Near-amorphous forms of high amylose maize starches are likely to undergo recrystallisation during the enzyme-digestion process. The mechanism of enzyme resistance of granular high-amylose starches is found to be qualitatively different to that for processed high-amylose starches. For all samples, measured levels of enzyme resistance are due to the interruption of a slow digestion process, rather than the presence of completely indigestible material.