[Physicochemical changes in starch during corn alkaline-cooking in varieties with different kernel hardness]

Changes in starch characteristics caused by alkaline-cooking in two corn genotypes (hard and soft) were studied in the present work. Color, pH, pasting properties (Brabender viscoamylograph), water sorption, solubility, swelling power and thermal analysis (Differential scanning calorimetry) were determined in starches previously extracted, from raw and alkaline-cooked hard and soft corns. A reduction in maximum viscosity peak, temperature at the endothermic peak and swelling power at 90 degrees C, and an increase in solubility was observed in starches obtained from both hard and soft corn after alkaline-cooking. Starch from hard corn showed an increment in initial pasting temperature after alkaline-cooking. Alkaline-cooking induced higher modifications in hard than in soft corn starch, probably as a result of its endosperm type and grain hardness, although optimum cooking times were used for each corn genotype.