Structural and thermal transitions during the conversion from native to granular cold-water swelling maize starch

• Published in: Carbohydrate polymers 2014-12, Vol.114, p.196-205
• Main Authors: Dries, D.M., Gomand, S.V., Goderis, B., Delcour, J.A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and medical sciences; Cold swelling; Differential scanning calorimetry; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; Natural polymers; Physicochemistry of polymers; Polarized optical microscopy; Starch; Starch - chemistry; Starch and polysaccharides; Starch and starchy product industries; Temperature; V-type crystallinity; Water - chemistry; X-ray diffraction; Zea mays - chemistry
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2014.07.066

•We report on the conversion of native to granular cold-water swelling maize starch.•This is achieved by an aqueous ethanol treatment at elevated temperature.•High temperature drying step is not necessary to impart cold-water swelling capacity.•The temperature necessary for the conversion increases with increasing ethanol:water ratio.•Amylose is almost exclusively responsible for V-type crystal formation. Native maize starch was gradually converted into granular cold-water swelling starch (GCWSS) by aqueous ethanol treatments at elevated temperatures. At a treatment temperature of 95°C, decreasing ethanol concentrations from 68 to 48% (v/v) led to decreased post-treatment gelatinization enthalpies in excess water, reflecting remaining original A-type crystals. Concomitantly to native A-type crystal melting, VH-type crystals appeared. At an ethanol concentration of 48%, a granular cold-water swelling maize starch was successfully produced. All crystals in its intact granules were of the VH-type and appeared birefringent when studied in ethanol under polarized light. Removal of all residual solvent by high temperature drying did not influence swelling power, proving that a high temperature drying step is not necessary to induce cold-water swelling capacity. Based on in situ calorimetric measurements, the thermal requirements to produce GCWSS from different ethanol:water mixtures were elucidated. This work is the first to demonstrate that the amylose fraction contributes almost exclusively to VH-type crystal formation in GCWSS.