PHASE STATE OF STARCH GELS AT DIFFERENT WATER CONTENTS

Amylose, amylopectin, their mixtures and pea starch gels have been investigated by means of thermomechanical analysis over a wide range of water contents. The phase state of gels obtained from natural and model three component systems (starch-water and amylose-amylopectin-water) depends on water content: at high water contents (>70 wt.% w.w.b.) such gels are biphasic and at low water contents (15-40 wt.%) monophasic. The values of the glass transition temperature obtained by extrapolation to zero water content using the Jurkov equation were similar for amylose and amylopectin. Gelation of high water content systems was determined by the immiscibility of amylose and amylopectin whereas gelation at low water contents was governed mainly by intermolecular interactions.