New insights into loss of swelling power and pasting profiles of acid hydrolyzed starch granules

摘要

The effect of acid hydrolysis on the swelling power of pea starch granules was studied by field emission SEM (FE-SEM). The swelling power of the native starch granules (g water absorbed/g dry starch) was 13, and this decreased to less than 2 after 1 day of acid hydrolysis. The proportion of the starch that was soluble in hot water increased from 15% for native starch to 75% after 1 day of hydrolysis. The swelling power of the starch decreased further, and solubility increased, with more extended hydrolysis. The decrease in swelling power and increase in solubility were attributed mainly to the disruption of side chains of amylopectin. Observations with FE-SEM indicated that starch granules were still able to melt and coalesce after 1 day of acid hydrolysis, but after 2 days solubilization of starch chains occurred predominantly rather than swelling when the granules were heated in excess water. The intactness of amylopectin is proposed to play a crucial role in the swelling power of starch granulesand in the structure of granule ghosts.