The role of alkali in sweet potato starch-Mesona chinensis Benth polysaccharide gels: Gelation, rheological and structural properties

According to the Chinese traditional black jelly production process, a critical step to ensure the quality of jelly is to add alkali to it. In this study, the effects of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) on the pasting, rheological, textural, and structural properties of sweet potato starch (SPS)-Mesona chinensis Benth polysaccharide (MCP) gels were evaluated. Adding Na2CO3 at low concentration reduced the final viscosity (FV) of SPS-MCP gels, whereas adding it at a high concentration increased the FV. Adding NaHCO3 can increase the FA/ of SPS-MCP gels in a concentration-dependent manner. Rheological results indicated that adding NaHCO3 at a low concentration decreased the storage modulus of SPS-MCP gels, whereas adding it at a high concentration increased the storage modulus. The storage modulus of SPS-MCP gels increased with increasing concentration of NaHCO3. The addition of Na2CO3 and NaHCO3 improved the textural properties of SPS-MCP gels and decreased the water mobility. Infrared results indicated that adding alkali can enhance the hydrogen bonding between SPS and MCP. Scanning electron microscopy results suggested that alkali can reduce the size of gels, and make the structure more compact. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the effects of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) on the properties of SPS-MCP gels. It was found that adding Na2CO3 at different concentrations had different effects on gel viscosity, while NaHCO3 increased the storage modulus of the gels. Additionally, alkali addition improved the textural properties of the gels and decreased water mobility.