Acid hydrolysis of native corn starch: Morphology, crystallinity, rheological and thermal properties

• Published in: Carbohydrate polymers Vol. 103; pp. 596 - 602
• Main Authors: Utrilla-Coello, R.G., Hernández-Jaimes, C., Carrillo-Navas, H., González, F., Rodríguez, E., Bello-Pérez, L.A., Vernon-Carter, E.J., Alvarez-Ramirez, J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15-03-2014; Elsevier
• Subjects: Acid hydrolysis; Applied sciences; Biological and medical sciences; Corn starch; Crystallinity; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; Kinetics; Morphology; Natural polymers; Physicochemistry of polymers; Starch and polysaccharides; Starch and starchy product industries; Acid hydrolysis; Kinetics; Crystallinity; Corn starch; Morphology; Viscoelasticity; Transition temperature; Chemical degradation; Experimental study; Chemical reaction kinetics; Starch granule; Hydrolysis; Oside polymer; Time curve; Chemical composition; Liquid solid reaction; Degradation product; Aqueous dispersion; Apparent viscosity; Heterogeneous reaction
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2014.01.046

•The acid hydrolysis of native corn starch was monitored for short and long times.•Amylose depletion of about 5% residual was obtained at the third day.•Maximum crystallinity was exhibited after 3 days.•Viscoelasticity was gradually reduced to achieve liquid-like behavior.
The acid hydrolysis of native corn starch at 35°C was monitored during 15 days. After this time, the residual solids were about 37.0±3.0%. First-order kinetics described the hydrolysis data, giving a constant rate of kH=0.18±0.012days−1. Amylose content presented a sharp decrement of about 85% and X-ray diffraction results indicated a gradual increase in crystallinity during the first 3 days. SEM micrographs showed that hydrolysis disrupted granule morphology from an initial regular shape to increasingly irregular shapes. Fractal analysis of SEM images revealed an increase in surface roughness. Fast changes in the thermal effects were caused by molecular rearrangements after fast hydrolysis of amylose in the amorphous regions in the first day. Steady shear rate and oscillatory tests showed a sharp decrease of the apparent viscosity and an increase of the damping factor (tan(δ)) caused by amylose degradation.