Xanthan gum is an extracellular polysaccharide secreted by the microorganism Xanthomonas campestris. Commercially it is manufactured by a fermentation process. Xanthan gum is soluble in cold water and solutions exhibit highly pseudoplastic flow and a synergistic interaction with galactomannans and glucomannans.

History

Xanthan gum was discovered by Allene Rosalind Jeanes and her research team at the United States Department of Agriculture, and brought into commercial production by CP Kelco under the trade name Kelzan in the early 1960s.It was approved for use in foods in 1968 and is accepted as a safe food additive in the USA, Canada, European countries, and many other countries.

Xanthan gum derives its name from the species of bacteria used during the fermentation process, Xanthomonas campestris.This is the same bacterium responsible for causing black rot to form on broccoli, cauliflower, and other leafy vegetables.

Preparation

Xanthan gum is produced by the fermentation of glucose and sucrose.The polysaccharide is prepared by the bacteria being inoculated into a sterile aqueous solution of carbohydrate(s), a source of nitrogen, dipotassium phosphate, and some trace elements.The medium is well-aerated and stirred, and the xanthan polymer is produced extracellularly into the medium. After one to four days, the polymer is precipitated from the medium by the addition of isopropyl alcohol, and the precipitate is dried and milled to give a powder that is readily soluble in water or brine.

It is composed of pentasaccharide repeat units, comprising glucose, mannose, and glucuronic acid in the molar ratio 2:2:1.

A strain of X. campestris has been developed that will grow on lactose - which allows it to be used to process whey, a waste product of cheese production. This can produce 30 g/L of xanthan gum for every 40 g/L of whey powder. Whey-derived xanthan gum is commonly used in many commercial products, such as shampoos and salad dressings.

Uses

Xanthan gum is used as a thickener or stabilizer in a wide variety of foods found on grocery store shelves. Many canned or prepared products contain xanthan gum: salad dressings, sauces, soups, and baked goods — particularly those that are gluten-free because xanthan gum can perform some of the same functions as gluten.

Xanthan gum is one of the most useful food additives around; it is effective in a wide range of viscosities, temperatures, and pH levels. It is easy to use, has no taste, and generally works quite well. And it can thicken liquids at extremely low concentrations – as little as 0.1% by weight can yield a thick liquid, and 0.5% by weight can make a thick paste (this is why it is best to weigh out xanthan gum with a digital scale rather than use volumetric measurements). Traditional thickeners like flour typically require far larger amounts to do a similar job. The quantity matters because the more thickener you have as a fraction of the total mixture the more likely it is to impose an undesirable texture and inhibit flavor.