Physicochemical characterization of rice, potato, and pea starches, each with different crystalline pattern, when incorporated with Konjac glucomannan

Abstract

The effect of Konjac glucomannan (KGM) on the gelatinization, retrogradation, rheological, and morphological properties of three starches (rice, potato, and pea starch) were investigated by multiple analytical techniques. Differential scanning calorimetry (DSC) data demonstrated that KGM delayed starch gelatinization and increased the gelatinization temperature of all three starches. KGM significantly decreased the gelatinization enthalpy change (ΔH1) of pea starch (PS) and potato starch (PtS), but increased that of rice starch (RS). Additionally, KGM effectively retarded retrogradation of the three starches, but to varying degrees. Rheological measurements revealed that KGM increased viscosity and viscoelasticity (G′ and G″) of all starch pastes. KGM decreased the loss tangent (tanδ) of potato starch, but increased the tanδ of rice starch and pea starch. Fourier transform-infrared spectroscopy (FT-IR) results suggested that the hydrogen bond force in the PtS-KGM mixture was stronger than in the PS-KGM and RS-KGM mixtures. Scanning electron microscopy (SEM) revealed that the microstructure was more dense and uniform in the starch-KGM pastes. Each of the three types of starch-KGM pastes had different morphologies as compared to their starch-alone counterparts as measured by the size, profile, and uniformity.