What Is Xanthan Gum?
Xanthan gum, also regarded as Xanthomonas gum, xanomonas polysaccharide, is a monospora polysaccharide produced by the fermentation of Pseudomonas Xanthomonas Campestris. Due to its special macromolecular structure and colloidal properties, Xanthan gum has become an excellent stabilizer, thickener and emulsifier for many products. It is widely used in food, daily chemicals, cosmetics and petroleum industries. Xanthan gum was discovered by scientists in 1963, and since then it has been well researched and subsequently confirmed to be a safe product. The US FDA approved xanthan gum as an unlimited food additive in 1969, and the European Economic Community approved it as a food emulsifier and stabilizer in 1980. Xanthan gum is a carbohydrate that cannot be broken down by our body, therefore, the body cannot digest xanthan gum and it does not provide any calories.
Source of Xanthan Gum
Xanthan gum is a microbial polysaccharide with a large production scale and wide application in the world. It is a fermented industrial product and mainly uses carbohydrates such as glucose, sucrose, starch, and corn as raw materials.In the 1960s, the United States first began commercial production of xanthan gum, and then France and Japan began to produce it successively, and China began commercial production in the 1980s. At present, xanthan gum can be produced on a large scale in the United States, China, France and Austria, and China’s production capacity ranks first in the world.
Production Process of Xanthan Gum
The initial step in the production of xanthan gum is the fermentation using a strain of Xanthomonas bacteria and substrate with sugar as carbon source, nitrogen, and salts (see Figure Producton Process). The resulting fermentation broth contains about 2–3% xanthan gum, which can be concentrated and purified by UF. This results in a UF retentate of 5–max. 10% concentrated high-molecular-weight xanthan gum and a UF permeate consisting mainly of water with some low-molecular-weight xanthan gum, salts, and sugars. This UF permeate stream can then be further treated by RO to obtain a pure water stream for recycling to the fermenter and a concentrated stream of low-molecular-weight xanthan gum, salts, and sugars. The concentrated xanthan gum in the UF retentate is further purified by precipitation in methanol. From the precipitation with methanol, the crude xanthan gum is recovered by decanter. The xanthan gum is then dried and milled resulting in a white to cream-colored free-flowing powder. The light phase of the decanter can be purified by UF recovering lost xanthan gum for recycling to the precipitation step and methanol for distillation recycling to the precipitation step.
Unique Advantages of Xanthan Gum
Xanthan gum has the properties of thickening, suspending, emulsifying and stabilizing. The number of pyruvic acid groups at the end of the molecular side chain of xanthan gum affects the performance of its application. 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 exhibits different properties under different conditions.
Suspension and emulsification
Xanthan gum has a good suspending effect on insoluble solids and oil droplets. Xanthan gum sol molecules can form super-bonded ribbon-shaped helical copolymers, forming a fragile glue-like network structure, so they can support the morphology of solid particles, droplets and bubbles, showing strong emulsification stability and high suspension ability.
Good water solubility
Xanthan gum can dissolve quickly in water and has good water solubility. In particular, it can be dissolved in cold water, which can save complicated processing and is easy to use. However, due to its strong hydrophilicity, if water is directly added without sufficient stirring, the outer layer will absorb water and swell into micelles, which will prevent water from entering the inner layer, thus affecting its function, so it must be used correctly. 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 to make a solution for use.
Xanthan gum solution has the characteristics of low concentration and high viscosity (the viscosity of 1% aqueous solution is equivalent to 100 times that of gelatin), which is an efficient thickening agent.
The aqueous solution of xanthan gum has high viscosity under static or low shear action, and under high shear action, the viscosity decreases sharply, but the molecular structure remains unchanged. When the shear force is removed, the original viscosity is restored immediately. The relationship between shear force and viscosity is completely plastic. The pseudoplasticity of xanthan gum is very prominent, which is extremely effective for stabilizing suspensions and emulsions.
Stability to heat
The viscosity of xanthan gum solution will not change greatly with the change of temperature. The viscosity of general polysaccharide will change due to heating, but the viscosity of xanthan gum aqueous solution has almost no change between 10-80 ℃, even if the low concentration of aqueous solution still shows stable high viscosity in a wide temperature range. The viscosity of 1% xanthan gum solution (containing 1% potassium chloride) was only reduced by 3% when heated from 25℃ to 120℃.
Stability to acid and alkali
Xanthan gum solution is very stable to acid and alkali, and its viscosity is not affected between pH 5 and 10. When the pH is less than 4 and greater than 11, the viscosity changes slightly. In the range of pH3-11, when the viscosity is larger, the difference between the smaller value 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, and these xanthan gum acid solutions are quite stable at room temperature, the quality will not change for several months. Xanthan gum is also soluble in sodium hydroxide solution and has thickening properties. The resulting solution is quite stable at room temperature. Xanthan gum can be degraded by strong oxidants, such as perchloric acid and persulfuric acid, and the degradation is accelerated with the increase of temperature.
Stability to salt
Xanthan gum solution is miscible with many salt solutions (potassium salt, sodium salt, calcium salt, magnesium salt, etc.), and the viscosity is not affected. At higher salt concentrations, its solubility is maintained without precipitation and flocculation even in saturated salt solutions, and its viscosity is hardly affected.
Stability to enzymatic hydrolysis
The stable double helix structure of xanthan gum makes it extremely resistant to oxidation and enzymatic hydrolysis. Many enzymes such as protease, amylase, cellulase, hemicellulase and other enzymes cannot degrade xanthan gum.
Application of Xanthan Gum in Food
As a food additive, xanthan gum has been accepted by many countries. This kind of polysaccharide can significantly improve the texture, taste and appearance quality of food by controlling the rheological behavior of the product, and improve its commercial value. It has become an important stabilizer, suspending agent, emulsifier, thickener, binder and high value-added, high-quality processing raw materials in the fields of beverages, cakes, jelly, canned food, seafood, and meat processing. Specifically, it can be summarized in the following aspects.
It is used in food of various fruit juice drinks, concentrated fruit juice, seasonings (such as soy sauce, oyster sauce, salad dressing). The stabilizing effect of xanthan gum is obviously better than that of other gums. It has strong thermal stability. General high temperature sterilization will not affect it. It can be used in various fruit juice drinks, pulp drinks, vegetable protein drinks, etc. The dosage is 0.08% ~0.3%. The excellent salt resistance, acid and alkali resistance of xanthan gum can completely replace the traditional thickener starch in soy sauce, etc., can overcome the shortcomings of starch precipitation, and can make the soy sauce fine and uniform, improve the wall hanging and coloring properties, and prolong the shelf life. For jam, bean paste and other flavored sauces, xanthan gum is used as a thickening stabilizer to make the sauce uniform, with good spreadability, no agglomeration, easy filling, and improved taste.
As an emulsifier, it can be used in various protein drinks, milk drinks, etc., to prevent oil-water stratification and improve protein stability, prevent protein precipitation, and can also use its emulsifying ability as a foaming agent and foam stabilizer, such as in beer manufacturing. After adding 0.02% xanthan gum to the soy protein-based emulsification system, the emulsification is obviously improved, and the mixed system has the characteristics of high shear rate and heat-induced high viscosity.
As a stable high-viscosity filler, it can be widely used in the processing of various kinds of snacks, bread, biscuits, candies and other foods, without changing the traditional flavor of the food, so that the food has better shape retention, longer shelf life and better taste are conducive to the diversification and industrial-scale production of these foods. In the production of various frozen foods, xanthan gum has the functions of preventing water loss, delaying aging and prolonging shelf life.
As an emulsion stabilizer, it is used in frozen food. In ice cream, xanthan gum can adjust the viscosity of the mixture, so that it has a uniform and stable composition, and the organization is smooth and soft. Due to the relationship between the viscosity and temperature of xanthan gum, it has plasticity and shear properties. Therefore, during the processing operation, the viscosity decreases and the resistance decreases, which is beneficial to the process, and in the cooling and aging stage, the viscosity recovers, which is beneficial to increase the expansion rate, prevent the formation of large ice crystals in the ice cream structure, and make the ice cream taste smooth and delicate. At the same time, the freeze-thaw stability of the product is improved, and the cream and water are evenly mixed during melting, and the phenomenon of slurry separation will not occur. The general aging time is 2 to 3 hours. The dosage is 0.2% to 0.4%.
Increase the toughness of flour products
Xanthan gum is an additive worthy of promotion in pasta products. In the production of dried noodles, ramen noodles and instant noodles, xanthan gum is added to enhance the gluten strength of the dough, the extruded dough pieces have toughness, reduce the breakage rate during drying, and improve the product taste at the same time, chewing with tendons, fresh and smooth. It can also save oil and reduce costs for frying. Adding xanthan gum to the quick-frozen dumpling wonton skin can improve the taste of the product, reduce the rotten skin and the degree of mixed soup. Adding 0.05% to 0.1% of the total amount of xanthan gum in the filling products can help preserve the water of the soup, ensure that the product is cooked thoroughly in the boiling water. The soup has a strong fragrance, and can improve its taste. Xanthan gum is used as an additive ingredient in bread, cakes, etc., which can increase the softness and prolong the shelf life of the product.
Application of Xanthan Gum in Petroleum Industry
A large market for xanthan gum is the petroleum industry. Oilfield chemicals are mainly polyacrylamide, CMC, modified starch, etc., resulting in high drilling cost and low oil yield. Xanthan gum is far stronger than other polymers in viscosity, thickening, salt resistance and pollution resistance, especially in drilling in oceans, beaches, high halogen layers and permafrost layers. Xanthan gum is used in mud treatment and completion fluids. It has obvious effects in terms of speeding up drilling, preventing oil wells from collapsing, protecting oil and gas fields, preventing blowouts, and greatly improving oil recovery.
Drilling fluid is the working fluid used in the drilling process. During the drilling process, the drilling fluid plays an important role. People often compare the drilling fluid to the “drilling blood”. Its functions are: suspending and carrying cuttings, cleaning the bottom of the well; Lubricate and cool the drill bit, increase the drill bit footage, and impact the formation through the drill bit water hole, which is conducive to breaking the rock; Form a mud cake to increase the stability of the well wall; Establish a liquid column pressure that can balance the formation pressure to prevent sticking, collapse and leakage , spray and other complex accidents. When using turbo drilling tools, it can be used as a liquid to transmit power. Xanthan gum is one of its main components, and its function is to increase the viscosity and shear force, and improve the suspension capacity of the drilling fluid, which is indispensable for the drilling fluid to perform its functions.
Among the various methods of enhanced oil recovery, polymer flooding plays an important role. The role of the polymer is to adjust the rheology of water injection, increase the viscosity of the driving fluid, and improve the sweep efficiency of water flooding. Reduce the permeability of formation water phase, so that water and oil can flow forward at a uniform speed. Such polymers must have excellent viscosity-increasing properties under reservoir conditions, and must have high viscosity retention under the effects of temperature, pressure and salt. Because xanthan gum solution has good viscosity, rheology, water solubility, chemical stability, and strong mechanical anti-degradation ability, it can be used as a displacement agent for oilfield production. Compared with the general hydrolyzed polyacrylamide, its physical and chemical properties are stable, its processing technology is simple, its oil displacement effect is good, its manufacturing cost is low, and it can selectively flow in the formation due to its good resistance to shear degradation.
Better oil displacement effect has been gradually applied to oilfield production as a displacement agent to improve oilfield recovery or as a chemical profile control agent to improve production effect. The physical simulation experiment further shows that xanthan gum has the effect of enhancing oil recovery, and is a kind of oilfield production displacement agent with excellent performance. After the primary and secondary extraction of oil is completed by conventional methods, more than 50% of the oil remains in the rock and cannot be recovered. Based on economic and energy considerations, people pay more and more attention to improving the oil recovery rate. The process of injecting water into petroleum rock formations is used for secondary oil production. Lots of dead oil residue. If a polymer with thickening properties is added to the injection fluid, the fluidity of water can be reduced, thereby increasing oil recovery. A variety of polymers can be used as flow control agents in oil recovery, among which xanthan gum is considered to have more potential. Xanthan gum has many of the basic conditions necessary to enhance oil recovery.
Xanthan gum is also used in fracturing fluids. It is mainly used as a thickener for water-based fracturing fluids and has the function of reducing friction.