3.6. Solubility of starches
Fig. 3 shows that degrees of solubility of the native normal and
high-amylose rice starches were less than 10% even at heating
temperature up to 90 C, whereas the solubility of the native waxy
rice starch was slightly higher when heating at 80–90 C. Starches
treated with citric acid and lactic acid had significantly higher
degrees of solubility, especially in hot water, as compared to the
native starches. The waxy rice starch treated with acetic acid also
rapidly increased its solubility when heating temperature was
more than 70 C, whereas the normal starches slightly increased
its solubility and the high-amylose starch did not change its solubility
when treated with acetic acid. The increase in the solubility
of the treated starches was due to the high amount of short chain
amyloses produced by acid hydrolysis, which easily dissociate and
diffuse out of granules during swelling (Tester & Morrison, 1990).