Impacts of guar and xanthan gums on pasting and gel properties of high-amylose corn starches

The effects of adding guar and xanthan gums on the pasting and gel properties of high-amylose corn starches, Hylon V (~50% amylose content) and NF-CG170 (~71% amylose content), were studied with waxy corn starch as a control, using an ultra-high temperature heating process (up to 130 °C) to gelatinize starches. Interaction between dispersed amylose and hydrocolloids contributed to the earlier onset of viscosity increase during pasting process (lower pasting temperatures) and strong synergistic effects in the peak, setback, and final viscosities with high-amylose starches, phenomena that were more pronounced when amylose content was higher. Conversely, addition of guar and xanthan gums to waxy corn starch resulted in higher pasting temperatures. After held at 5 °C for 2 h, the gelatinized high-amylose starch/hydrocolloid formed stronger and more elastic gels (higher G' and tanδ) with denser microstructure and thicker gel skeleton, compared to starch alone. Compared to xanthan gum, guar gum displayed a much stronger synergistic effect with Hylon V in gel strength, while their difference in synergistic effect was less pronounced with NF-CG170, indicating that amylose dominated gel properties when at a high content (i.e., ~ 71% in starch).