Cereal Chem 67:558-563 | VIEW
Swelling and Gelatinization of Cereal Starches. II. Waxy Rice Starches.
R. F. Tester and W. R. Morrison. Copyright 1990 by the American Association of Cereal Chemists, Inc.
The swelling and gelatinization properties of waxy rice starches (essentially pure amylopectin) were studied. Low gelatinization temperature (low-GT, 64-67 C), intermediate-GT (68-71 C), and high-GT (75- 79 C) starches exhibited a range of swelling factors at 80 C (low = 24-42, intermediate = 28-42, high = 29- 40; maximum values were not attained by the high-GT starches). Structural analysis showed that the low- GT and high-GT starches has very similar chain lengths after debranching of insoluble residues after lintnerization. The low-GT starches could be annealed to behave like high-GT starches, but the latter also responded a little to annealing. It is concluded that the low-GT starches have less crystallinity and less perfect crystallites than the high-GT starches due to minor structural differences in their amylopectins. Partial hydrolysis of amorphous regions caused a large decrease in swelling factor but had only a small effect on gelatinization enthalpy. It is suggested that crystallites within the amylopectin molecule determine the onset of swelling and gelatinization, and that maximum swelling factors may relate to the molecular weight and shape of the whole amylopectin molecule.