0.2-0.3% xanthan gum is a common ingredient in my emulsions. I use this natural polymer mainly as a stabiliser. Xanthan, with it’s shear thinning, and high low-shear viscosity, is able to reduce the tendency of droplets to coalesce minimising the chances of emulsion separation.
I use natural gums, including xanthan, frequently. They can be superior to synthetic polymers in many ways as they can tolerate electrolytes and be effective over a wide pH range. On the other hand, natural gums, if used at a high concentration primarily to thicken, can be sticky, slimey, stringey and snotty. These issues can be minimised by reducing the concentration and mixing the gum with other types, for example, blending 0.3% xanthan gum with 0.3% sclerotium gum and 0.3% sodium alginate.
Xanthan gum is available in a wide variety of grades. Some grades provide more viscosity, transparency and are less likely to clump than other grades. A common issue formulators encounter is trying to avoid the gum forming swollen lumps, known as fish eyes. This occurs when the individual gum particles which were not properly dispersed stick together and the outer surface rapidly hydrates. To overcome this we can either, before adding the water using high shear, pre-mix the gum in a glycol or put it in the oil phase. Alternatively, we can use a surface-treated grade which makes the gum temporarily insoluble thereby facilitating dispersion. My favourite grade of xanthan gum is Cosphaderm® X 34 made by Cosphatec, which I find a breeze to disperse and hydrate. Cosphatec also market their xanthan as having a greater ability to stabilise emulsions compared to other grades. KELTROL® CG-SFT is another popular grade providing a smooth flow and transparency.