Effects of guar gum and xanthan gum additions on physical and rheological properties of cationic tapioca starch

The gelatinization of cationic tapioca starch embedded in gum matrices was investigated by using a Rapid Visco-Analyzer (RVA), differential scanning calorimeter (DSC), scanning electron microscope (SEM), and rheometer. In addition, swelling power and solubility indices were measured. Xanthan and guar gum increased the RVA peak viscosity of cationic tapioca starch during pasting synergistically in different ways. Guar gum was more effective than xanthan gum in terms of increasing peak viscosity due to its ability to increase the swelling power and solubility index. Both xanthan gum and guar gum induced association between the gelatinized granules probably due to bridging. Association was much more extensive with xanthan. DSC studies showed that the presence of gums influenced the gelatinization characteristics of starch significantly by increasing the onset gelatinization temperature and decreasing the gelatinization enthalpy. Dynamic rheological measurement showed a strong interaction occurred in the cationic tapioca starch-xanthan gum mixture resulting in a decrease in the loss tangent (tan delta) as compared with guar gum addition or starch alone. The ionic interaction of gums and starch was found to play an important role in the gelatinization characteristics of the mixtures and also rheological properties of the pastes. (C) 2005 Elsevier Ltd. All rights reserved.