Views: 0 Author: Site Editor Publish Time: 2022-10-21 Origin: Site
Xanthan gum, also known as Hansen gum. It is an extracellular polysaccharide produced by Xanthomonas campestris with carbohydrate as the main raw material (such as corn starch) through fermentation engineering. It has unique rheological property, good water solubility, stability to heat, acid and alkali, and good compatibility with a variety of salts. As a thickener, suspension agent, emulsifier, and stabilizer, it can be widely used in more than 20 industries such as food, petroleum, medicine, etc. It is the largest microbial polysaccharide produced in the world and has extremely wide applications.
Xanthan gum is an extracellular acidic heteropolysaccharide produced by fermentation of Xanthomonas. It is a polysaccharide macromolecular compound composed of D-glucose, D-mannose and D-glucuronic acid in a ratio of 2:2:1, with a relative molecular weight of more than 1 million. The secondary structure of xanthan gum is the reverse winding of the side chain around the main chain skeleton, which is maintained by hydrogen bonds to form a rod like double helix structure.
Xanthan gum is a light yellow to white flowable powder with a slight odor. Easily soluble in cold and hot water, neutral solution, resistant to freezing and thawing, insoluble in ethanol. It is dispersed and emulsified with water to become a stable hydrophilic viscous colloid.
Xanthan gum is currently the most superior biological glue in the world, which integrates thickening, suspension, emulsification and stability. The number of pyruvate groups in the end of the molecular side chain of xanthan gum has a great influence on its properties. Xanthan gum has the general properties of long chain polymers, but it contains more functional groups than general polymers, and will show unique properties under specific conditions. Its conformation in aqueous solution is diverse, and it shows different characteristics under different conditions.
1. Suspension and emulsification
Xanthan gum has good suspension effect on insoluble solids and oil droplets. Xanthan gum sol molecules can form super binding ribbon helical copolymers, forming a fragile network structure similar to glue, so it can support the morphology of solid particles, droplets and bubbles, showing strong emulsification stability and high suspension capacity.
2. Good water solubility
Xanthan gum can be quickly dissolved in water and has good water solubility. It can also be dissolved in cold water, which can save complicated processing process and is convenient to use. However, due to its strong hydrophilicity, if the water is directly added and the mixing is not sufficient, the outer layer will absorb water and expand into a micelle, which will prevent the water from entering the inner layer, thus affecting the function. Therefore, attention must be paid to the correct use. The xanthan gum dry powder or dry powder auxiliary materials such as salt and sugar are mixed well and then slowly added to the stirring water for feeding to make a solution for use.
3. Thickening property
Xanthan gum solution has the characteristics of low concentration and high viscosity (the viscosity of 1% aqueous solution is 100 times that of gelatin), and it is a highly effective thickener.
Xanthan gum aqueous solution has high viscosity under static or low shear action, and shows a sharp decline in viscosity under high shear action, but the molecular structure remains unchanged. When the shear force is eliminated, the original viscosity will be restored immediately. The relationship between shear force and viscosity is completely plastic. Xanthan gum has outstanding pseudoplasticity, which is very effective for stabilizing suspensions and emulsions.
5. Thermal stability
The viscosity of xanthan gum solution will not change greatly with the change of temperature. Generally, the viscosity of polysaccharides will change due to heating, but the viscosity of xanthan gum aqueous solution almost does not change between 10-80 ℃. Even the low concentration aqueous solution still shows a stable high viscosity in a wide temperature range. The 1% xanthan gum solution (containing 1% potassium chloride) was heated from 25 ℃ to 120 ℃, and its viscosity only decreased by 3%.
6. Stability to acids and bases
Xanthan gum solution is very stable to acids and bases, and its viscosity is not affected when the PH is 5-10. The viscosity changes slightly when the PH is less than 4 and more than 11. Within the range of PH3-11, the difference between the maximum viscosity and the minimum viscosity is less than 10%. Xanthan gum can be dissolved in a variety of acid solutions, such as 5% sulfuric acid, 5% nitric acid, 5% acetic acid, 10% hydrochloric acid and 25% phosphoric acid. These xanthan gum acid solutions are quite stable at room temperature, and the quality of the parts will not change for several months. Xanthan gum can also be dissolved in sodium hydroxide solution and has thickening property. The solution formed is very stable at room temperature. Xanthan gum can be degraded by strong oxidants, such as perchloric acid and persulfuric acid, and the degradation accelerates with the increase of temperature.
7. Stability to salt
Xanthan gum solution can be miscible with many salt solutions (potassium salt, sodium salt, calcium salt, magnesium salt, etc.), and the viscosity is not affected. Under the condition of high salt concentration, even in saturated salt solution, it still maintains its solubility without precipitation and flocculation, and its viscosity is almost unaffected.
8. Stability to enzymatic hydrolysis
Xanthan gum has a stable double helix structure, which makes it have strong antioxidant and anti enzymolysis capabilities. Many enzymes, such as protease, amylase, cellulase and hemicellulase, cannot degrade xanthan gum.