Molecular degradation of rice starch during processing to flakes

Roasting of the soaked paddy (roasting-parboiling) appeared to cause an increase in the
proportion of the high-molecular-weight component of starch, separated in Fraction-I, probably due
to retrogradation. The solubility of starch also decreased. Flaking of roasted-parboiled paddy in the
traditional edge-runner Øaker did not cause any further appreciable change in the proportion of
Fraction-I and Fraction-II. Flaking in the roller-Øaker unit, on the other hand, caused a decrease in the
proportion of Fraction-I, indicating molecular breakdown of starch. The total starch solubility
increased marginally in edge-runner Øakes but substantially in roller-Øaker Øakes. Fractionation of
starch that was soluble in hot water showed that the major amount of amylose equivalent resided in this
portion as revealed by a higher proportion of Fraction-II and a high lmax of the peak of this fraction.
When retrogradation was induced in the Øakes under appropriate conditions of moisture and
temperature, the content of the high-molecular-weight Fraction-I of total starch increased slightly in
edge-runner Øakes but markedly in roller-Øaker Øakes, indicating an aggregation or reassociation of
starch molecules or its fractions.