Interactions between tapioca starch and Mesona chinensis polysaccharide: Effects of urea and NaCl

Non-starch polysaccharide and starch interactions have been extensively studied. However, few researches focus on their interactions mechanism. In this study, the effects of hydrogen bond and electrostatic interactions on the tapioca starch-Mesona chinensis polysaccharide (TM) gels were investigated. The results of pasting and thermal experiments (heating phase) showed that the peak viscosity (PV) of TM gels increased with the addition of urea. The addition of urea caused the hydrogen bonds to be destroyed and the rearrangement of starch during cooling was inhibited, which led to the final viscosity of TM gels decreased. The interactions between 0.5% NaCl and starch hydroxyl groups resulted in a significant increase in PV, while excessive addition of NaCl produced an electrostatic shielding effect, resulting in a decrease in PV, but still higher than TM gels. The results of rheological, texture, and particle size experiments (gel cooling stage) showed that hydrogen bond played a decisive role in the final texture of TM gels. Scanning electronic microscopy results showed that the addition of urea loosened the starch structure, and the high concentration of urea caused the structure appear fragmented.