DYNAMIC RHEOLOGICAL STUDIES ON AN INTERACTION BETWEEN LIPID AND VARIOUS NATIVE AND HYDROXYPROPYL POTATO STARCHES

Dynamic rheological measurements and differential scanning calorimetry (DSC) were used to investigate the interaction between starches and lipid. The starches used were waxy maize starch, native potato starch, and hydroxypropyl potato starches with varying molar substitution (MS). The lipid chosen was a monoglyceride, monomyristin (MGM). A Brabender amylograph was used to prepare starch pastes with and without MGM. The rheological behaviour of the starch pastes was evaluated after the preparation, and during heating and subsequent cooling. The influence of an addition of MGM on the rheological behaviour was much higher for the native potato starch than for the waxy maize starch, and decreased as the MS of hydroxypropyl potato starches increased. On heating, waxy maize starch-MGM paste gave one rheological transition at temperatures below about 65-degrees-C. Native potato starch and hydroxypropyl potato starch (MS 0.045)-MGM pastes showed two rheological transitions, one of which had a similar temperature range to that of the waxy maize starch-MGM paste. The other one, which was observed as a sharp decrease in the storage modulus (G') and an increase in the phase angle (delta), provided rheological evidence for the dissociation of an amylose-MGM complex, and it occurred at nearly the same temperature as the endothermic transition of the amylose-MGM complex measured by DSC. On cooling, this rheological behaviour of the starch-MGM pastes was reversed, indicating that an association between starch and MGM took place. The results of this study gave further rheological evidence for an interaction between amylopectin and MGM.