Abstract
The cooking and processing characteristics of pregelatinized hydroxypropylated wheat starch were studied by determining the physicochemical properties of viscosity and gelling. The effects of adding pregelatinized hydroxypropylated wheat starch to sponge cake were then measured in terms of viscosity, texture and a sensory evaluation.
A thermal analysis in excess water indicated that, compared with unmodified wheat starch, the hydroxypropylated wheat starch had a lower pasting temperature range and a pasting energy reduced to about 1/2. These data suggest that the hydroxypropylated wheat starch could be easily pasted. Viscography indicated that the hydroxypropylated wheat starch had an onset temperature for viscosity increase that was lower by about 27°C than that of unmodified wheat starch, with a maximum viscosity about twice as high. The addition of sucrose caused a significant increase in viscosity, while the addition of an acid caused an initial increase in viscosity and then a decrease in stability while heating and stirring. Little difference was observed in viscosity in the concentration range of 5.0-8.0%, suggesting some restricted swelling of the little-modified starch at high concentrations. The viscosity of the pregelatinized hydroxypropylated wheat starch paste was decreased by adding an acid or sucrose. With cake batter, the viscosity was elevated with increasing addition of pregelatinized hydroxypropylated wheat starch. Compared with a control sample, the sponge cake prepared by adding pregelatinized hydroxypropylated wheat starch had a soft texture, good moisture retention and little increase in firmness during cold storage. The sensory evaluation showed no significant difference in likeability between the control and test samples.
