If you leave a lettuce in the fridge for too long it gets a rather interesting texture. Its sort of lubricious and a bit slimy but not actually wet. This is the result of a bacteria that takes part in the very early stages of breaking down vegetable matter. The bacteria is called Xanthomonas campestris and the feeling is the result of a material it exudes called xanthan gum. Xanthan gum is now made by fermenting the bacteria with sugar and harvesting the resulting slime. I would love to know who thought of doing this. My reaction would have simply been to throw the lettuce away. The slimy extract is dried into a powder. This can be reconstituted by simply adding it to water.
The main use of xanthan gum is in the food industry where it is used as a suspending agent in sauces and pastes. In cosmetics it is used at much lower levels usually in combination with other stabilisers. The beauty of xanthan is that a very small amount, sometimes as low as 0.1%, can stabilise an otherwise unstable formulation. It does this this by highly efficiently filling space. The xanathan molecule is highly branched in structure and the molecules tend to repel one another. I haven’t seen it done for a good many years now, but reps for the companies that make xanthan used to suspend a golf ball in water at trade shows to demonstrate just how good it is as a suspending agent.
All in all, a useful and quite unusual raw material and one that every cosmetic chemist is very familar with. For users, I doubt you’ll notice anything much about products containing xanthan gum, but at least you’ll know what it means if you see it on an ingredient list.
Notes for Chemists
Xanthan is used in pharmaceuticals and is listed in the European Pharmacopeia and has a latin name there, gummi xanthanum. Other than that it is mercifully short of synonyms. It is always called xanthan gum as per its ICID name and has a CAS number of 11138-66-2 and an EINECS number of 234-394-2. There are no health issues with it and even the Skin Deep database can find no fault with it.
For a synthetic but very elegant cosmetic thickener, have a look at my review of carbomer.