Effect of heating–cooling on rheological properties of tapioca starch paste with and without xanthan gum

The effect of xanthan gum (Xan) on pasting and gelatinization behavior of tapioca starch (TS) was investigated. Rheological measurements of TS/Xan mixtures with 5% w/w total polysaccharide concentration at different mixing ratios (10/0, 9.5/0.5, 9/1 and 8.5/1.5) were performed to understand the pasting and gelatinization behavior of TS with and without Xan on heating–cooling cycle using a Rapid Visco Analyzer (RVA) and conventional rheometers. Xan increased storage modulus (G′) and loss modulus (G″) of TS dispersions during gelatinization process. Pastes of TS/Xan tended to be more solid-like, i.e., G′ larger than G″, with increasing Xan. The G′ of TS/Xan paste increased when kept at 10 °C indicating the network formation. Pasting temperatures, peak viscosity, final viscosity and breakdown values of TS increased with increasing Xan content but the opposite result was observed in setback value from RVA measurement. Temperature dependence of steady shear viscosity became less pronounced with increasing Xan content on both cooling and reheating indicating that Xan made the mixture more thermally stable. All the results suggest that the sample preparation and measuring conditions influence the rheological properties of TS/Xan mixtures, which should be taken into account in food application.

Left: Temperature dependence of steady shear viscosity of 5% w/w TS/Xan mixtures: 9.5/0.5 and 8.5/1.5 shear rate: 10 s−1. ① Heating from 10 to 95 °C, ② cooling from 95 to 10 °C, ③ and finally reheating from 10 to 95 °C at the rate of 1 °C/min.Figure optionsDownload as PowerPoint slideRight: Temperature dependence of G′ and G″ of 5% w/w TS/Xan pastes 9.5/0.5 and 8.5/1.5. ① Cooling from 90 to 10 °C and ② subsequently heating from 10 to 90 °C (frequency: 1 rad/s, scan rate at 1 °C/min, 5% strain).Highlights
► Concentration and mixing ratio.
► Shear conditions during heating and cooling in the rheological measurement and in the sample preparation.
► Large deformation or small deformation.