Effects of lyophilization and low-temperature treatment on the properties and conformation of xanthan gum

Xanthan molecules possess an ordered helical conformation in a solution, and this conformation can be changed by varying the temperature. Currently, only very few studies have assessed the effect of the low temperatures on the conformation of xanthan. We determined the structure, interfacial properties, and hydrophobicity of xanthan at a low temperature using XRD, FTIR, pendent drop, and fluorescence spectroscopic analysis. Furthermore, we explored the conformational changes in xanthan using DLS, rheometer, and AFM. We found that the properties of xanthan had been changed at a low temperature compared to a xanthan sample at room temperature. Our results suggest that the portion of the double-helix in xanthan increases when the temperature is decreased; the molecules will aggregate after lyophilization, and then the properties, such as interfacial tension and hydrophobicity, will be changed.