Characterization of ulvan polysaccharide extracted from Ulva pertusa and its effect on thermal, rheological, and gelling properties of rice flour

Three ulvan fractions (UPs 1-3) were extracted from Ulva pertusa via hot-water extraction. UP1 exhibited a molecular weight of 729,151 Da, while UPs 2 and 3 ranged from 19,952 to 750,384 Da. These fractions differed in monosaccharide, uronic acid, and sulfate levels. Zeta potentials for polysaccharide solutions (0.2-0.6 % w / v ) ranged from-34.4 to-25.1, all demonstrating shear-thinning behavior. Incorporating UPs 1-3 solutions (0.2-0.6 % w/v) with rice flour increased gelatinization temperatures and modified pasting properties, increasing peak time, peak viscosity, and trough viscosity while reducing breakdown, final, and setback viscosities. Ulvan polysaccharide improved the viscous behavior of rice flour paste, indicated by increased loss modulus and tan delta (p > 0.05). Furthermore, ulvan polysaccharide improved the microstructure and texture of rice flour gel, with UP1 (0.6 % w/v ) forming denser matrices and better texture. Molecular docking analysis suggested that hydrogen bonding is the primary interaction between rice glutelin and ulvan components.