Influence of Low Acyl and High Acyl Gellan Gums on Pasting and Rheological Properties of Rice Starch Gel

The pasting, viscoelastic, morphological and retrogradation properties of rice starch as affected by low acyl (LA) and high acyl (HA) gellan gums were studied. The additions of both LA and HA gums increased the peak and trough viscosities, while decreased the final and setback viscosities of rice starch paste. The starch-HA mixed pastes exhibited superior viscoelastic properties to the starch-LA pastes as evidenced by their higher storage modulus and lower loss tangent values. The starch-HA system exhibited higher resistance to the stress and more pronounced recovery rate in in-shear structural recovery test. The creep recovery data were well fitted by a 4-element Burger's model. The shrinkage measurements showed that the addition of both hydrocolloids, especially the HA gellan gum retarded the retrogradation of rice starch gel during cold storage. It was concluded that the addition of LA and HA gellan gums modified the rheology and textural properties of rice starch gel in different ways and interacted under different mechanisms based on their molecular structures.