Effect of soybean soluble polysaccharide on the pasting, gels, and rheological properties of kudzu and lotus starches

Abstract

The effect of soybean soluble polysaccharide (SSPS) on the pasting, gels and rheological properties of kudzu and lotus starches was investigated. The structures of starch/SSPS mixtures after gelatinization were investigated by scanning electron microscopy (SEM), wide-angle X-ray diffraction (XRD), and confocal laser scanning microscopy (CLSM). The substitution of kudzu and lotus starches with SSPS reduced the peak viscosity and increased the gel stability according to rapid visco analysis, while SSPS resulted in an increase in freeze-thaw syneresis. Indeed, the SEM analysis of the starch/SSPS samples showed small ditches on the sample surfaces. Moreover, a significant drop (P < 0.05) in the hardness of the starch/SSPS gels was observed. The addition of SSPS promoted the formation of the B-type crystal structure in starch/SSPS mixtures. In addition, the rheological results also showed that the mixtures of starch/SSPS yielded more liquid-like behavior than the controls did (G' > G″). The data for the steady shear viscosity were modeled with the power-law equation, and the flow behavior index (n) was n < 1, signifying pseudoplasticity, where the consistency coefficient decreased in the presence of SSPS, suggesting lower viscosity. CLSM results confirmed the formation of a SSPS “barrier” at the surface of the starch granule ghosts to inhibit amylose leaching. These data directly or indirectly indicated that SSPS can affect the pasting behavior of kudzu and lotus starches, which ultimately can affect the gel texture and overall acceptability.