Aggregate Formation and Segregation of Maize Starch Granules Cooked at Reduced Moisture Conditions

Abstract

The mechanism of formation of aggregates of maize starch granules was studied through the kinetics of their destruction. The cooking of the starch, which was done with limited amount of water (1:1) to imitate the conditions of starch foods, induced the formation of aggregates of different sizes. These were dispersed in ethanol and agitated for different periods, provoking their desegregation. The size distribution and its dependence on time was measured by means of laser light scattering. It was found that the aggregates are built in a fractal-type geometry: a group of starch granules conform a small aggregate, then groups of the latter build into larger ones, and so on, observing up to five scales, depending on the cooking degree. The aggregates are held together by gelatinized granules that show no Maltese cross. The formation of the aggregate classes can be explained by granules swelling ramdomly at different points of the sample, with a lower probability of dual gelatinization of neighbor granules.