Insights into viscosity, rheology, microstructure, and in vitro digestibility of Cyperus esculentus starch-Sanxan Gum mixtures

Abstract

Hydrocolloids are effective in modulating the processing characteristics of native starches, with their efficacy depending on the structural properties of the colloid. This study focused on the effects of different Sanxan gum (SG) concentrations on multiple dimensions of Cyperus esculentus starch (CES), including viscosity, rheology, structural properties, and in vitro digestibility. Viscosity results indicated that SG reduced the peak temperature (70.60–69.07 °C), peak viscosity (372.50–346.69 BU), and breakdown value (89.00–23.00 BU) of CES gels, while increasing the setback value (220.00–232.33 BU), with this effect becoming increasingly pronounced at higher SG concentration. The rheological experiments further revealed that the addition of SG reduced the apparent viscosity, storage modulus (G′), and loss modulus (G″) of the CES, and this trend gradually weakened with increasing SG concentration, showing a clear concentration-dependent relationship. The textural analysis showed a progressive increase in hardness from 16.55 g to 26.70 g. SEM results exhibited network formation; at low SG levels, the mixtures showed irregular voids, while high SG levels yielded homogeneous and dense networks. This morphological evolution was critical for enhancing the structural stability and processing properties of the CES. In addition, the in vitro digestibility of CES was significantly reduced by the addition of SG, which improved its nutritional and functional properties (RDS 79.11 %–71.08 %, SDS 5.85 %–6.82 %, RS 15.04 %–22.10 %). This study not only elucidates the potential interaction mechanism between SG and CES, but also lays a theoretical foundation for broadening the application of CES.