INTENSIFICATION OF STARCH GRAIN DESTRUCTION, GELATINISATION AND HYDROLYSIS IN WATER-STARCH SUSPENSION DURING MECHANICAL PROCESSING

The processes of potato starch swelling, dispersion, dissolution and hydrolysis during thermal heating of water - starch suspension in a thermal shaker and during mechanical treatment in a hydro-pulse reactor are considered. The conditions of mechanical treatment and heating were chosen to provide the same heating rates of the suspension in both installations. This allowed us to separate the influence of thermal and mechanical effects on starch grains and to find that during mechanical processing at temperatures below gelatinisation point, dispersion of starch grains occurs, followed by gelatinisation, while when heated, at first gelatinisation of starch grains occurs, and then their destruction is observed. It is shown that under mechanical action about 70 % of amylose from starch granules passes into solution after treatment for 40 min, while no noticeable release of amylose into the solution is observed as a result of thermal treatment for the same time. It is found that during mechanical processing of the water-starch suspension, both amylose and amylopectin are immediately released into the solution, while during heating, amylose is primarily dissolved, and only after heating the suspension for 340 min at 95 °C the dissolution (leaching) of amylopectin begins. The rate of the initial stage of acid hydrolysis of starch at 90 °C and pH 2.4 under mechanical processing is approximately 3 times higher than in the case of suspension heating in the thermal shaker. With longer treatment, the rate of mechanochemical acid hydrolysis decreases and becomes only 1.3 times higher than the rate of thermal hydrolysis.