ABSTRACT
The acetyl and pyruvate groups can be selectivity removed [23]. The pyruvate groups can be removed by heating a xanthan gum solution in presence of oxalic acid for a few hours. To remove the acetyl groups, adding potassium hydroxide to a solution of xanthan gum at room temperature for few hours would be sufficient [24]. Acetyl groups tend to stabilize the ordered form, presumably by promoting association of the side chains with the backbone through hydrogen bonding. Pyruvate groups, in contrast, tend to favor the disordered form because electrostatic repulsion between these groups is minimized when the side chains extend away from the backbone [24]. This effect is clearly seen in studies using xanthan gum and xanthan gum derivatives [25]. The order of thermal stability based on experimental data of the ordered conformation is the following, pyruvic-free>native xanthan> acetyl and pyruvic-free>acetyl-free.
