Guar and xanthan gum differentially affect shear induced breakdown of native waxy maize starch

Starches and non-starch hydrocolloids or gums are used very often as texturizers in the food industry. The aim of this work was to investigate the effects of guar gum and xanthan gum on the mild temperature pasting behavior of waxy maize starch. Waxy maize starch dispersions containing either guar, xanthan or no gum were pasted at temperatures (70 and 72.5 °C) close to the gelatinization temperature by means of the starch pasting cell mounted on the rheometer. Different shear conditions were imposed (no shear, 50 s−1 and 150 s−1). Along with the pasting behavior, the particle size distribution of the swollen granules was derived by means of laser light scattering and the rheological behavior of the cooled pastes was determined to characterize the samples. Finally, confocal laser scanning microscopy was used to locate the fluorescently labeled gums in the swollen starch dispersions. Under the given conditions, both gums differently affected the starch during the heating steps. While xanthan gum lowered the shear induced breakdown of the granules, guar gum did not show this specific property. Consequently, guar gum primarily modified the rheological properties of the pastes by its presence in the continuous phase, whereas xanthan gum also induced indirect effects by better preserving the granular structure.