2 Xanthan Gum A polysaccharide Used as food additive & rheology modifier.Production involves fermentation of glucose or sucrose by the bacterium, Xanthomonas campestris
3 STRUCTUREM.W. varies from ~ 1 million - 50 million depending upon preparationBackbone:2 β-D-glucose units linked through the 1 and 4 positions.Side chain:2 mannose units & 1 glucuronic acid unitLinked to alternate glucose of the backbone at the 3 position.In all, thus, the chain has repeating modules of five sugar units.
4 The other mannose unit has an acetyl group at the 6 position. 40-50% of terminal mannose units have a pyruvic acid group linked as a ketal to its 4 & 6 positions.The other mannose unit has an acetyl group at the 6 position.2 of these chains aligns to form a double helixA rigid rod configurationHigh efficiency as a viscosifier of water
6 PreparationInoculating a sterile aqueous solution of carbohydrate(s), a N2 source, dipotassium monohydrogen phosphate & some trace elementsMedium is well-aerated & stirredXanthan is produced extracellularly in the mediumFinal concentration of xanthan: 3-5% by weightFermentation for ~ 4 daysPrecipitation of Xanthan from the medium by addition of isopropyl alcoholDried and milled to give a powder that is readily soluble in water or brine.
7 Applications Even 1% can greatly increase in the viscosity of a liquid In foods, used at 0.05 – 0.5%.Viscosity decreases with high shear rates (mixing, shaking, chewing): PseudoplasticityIn salad dressings & saucesThicker at rest in the bottle to keep the mixture homogeneousShear forces due to shaking thins it, so, easily pouredAfter exiting the bottle, no shear force. So, thickens back & clings to salad.Stable under a wide range of temperatures and pH
8 In frozen foods and beverages, creates the pleasant texture Helps to stabilize the colloidal oil and solid components against creaming.In frozen foods and beverages, creates the pleasant textureIn toothpaste, serves as a binder to keep the product uniformIn gluten-free baking, to give the dough / batter a "stickiness"Gluten in wheat to be omittedFor thickening liquids for those with swallowing disorders, since it does not change the color or flavor of foods or beverages.
9 In the oil industry, to thicken drilling fluids Fluids serve to carry the solids cut by horizontal drilling bit back to the surfaceAlso been added to concrete poured underwater, in order to increase its viscosity and prevent washout.In cosmetics, to prepare water gels usually in conjunction with bentonite clays.In oil-in-water emulsions to help stabilise the oil droplets against coelesenceHas some skin hydrating properties.