Structural Characteristics of Xanthan Gum
Molecular Structure of Xanthan Gum
Xanthan, also known as xanthan gum, is an extracellular acidic polysaccharide secreted by Xanthomonas campestris. In the molecular structure of xanthan gum, some of the mannose at the 4,6 C position of the side chain ends is attached to a pyruvate group, while some of the mannose attached to the main chain is acetylated at C-6. The removal of acetyl and pyruvate groups from xanthan gum significantly alters its properties. The variety of xanthan gum and the post-fermentation processing determine the content of pyruvate and acetyl groups. The dissolved oxygen level during fermentation significantly affects the pyruvate content; generally, xanthan gum with a low dissolved oxygen rate has a low pyruvate content.
Conformation of Xanthan Gum
Studies have shown that the branch located at the C-3 position on the D-glucose main chain is the main component of the xanthan gum conformation. They may fold and attach to the main chain backbone, thus stabilizing the helical structure and protecting it from external environmental influences. Xanthan gum generally exhibits three conformations in aqueous solutions: natural xanthan gum may have a relatively regular double helix structure; after prolonged heat treatment, the xanthan gum helical chains extend into a disordered coiled chain structure; this temperature range is usually called the conformational transition temperature; after cooling, both the helical and coiled chains exist to a considerable extent in the system.
Properties of Xanthan Gum
The unique structural characteristics of xanthan gum determine its excellent physicochemical properties. Xanthan gum is odorless, non-toxic, has antioxidant properties, high safety, and is readily soluble in water. In aqueous solutions, it exists as a polyanion, exhibiting good stability, compatibility, and stability. Specifically, it exhibits the following characteristics: high viscosity in low-concentration solutions; rheological properties (pseudoplasticity), with viscosity decreasing significantly with increasing shear rate and immediately recovering to its maximum as shear rate decreases; stability (stable to temperature, salt, acid, and alkali; resistant to oxidation and enzymatic hydrolysis), maintaining essentially constant viscosity within the temperature range of 28–80℃ and pH 1–11; high salt tolerance, suitable for use in foods such as soy sauce; suspending properties, providing excellent suspension of insoluble solids and oil droplets; compatibility, synergistic effects, and compatibility with most food gums, various food ingredients, and food additives, producing synergistic effects; good miscibility within the same solution system; beneficial synergistic effects with mixtures of guar gum, locust bean gum, alginate, and CMC-Na, resulting in a significant increase in viscosity and the formation of gels with varying toughness.
Blending Effects of Xanthan Gum with Other Gum
Blending Xanthan Gum with Konjac Gum
Konjac gum is generally white, has the characteristic odor of konjac, and contains a small amount of impurities. Its main component is Konjac Glucomannan (KGM). Konjac gum exhibits pseudoplasticity and is a heat-irreversible gel, widely used in the manufacture of konjac cakes and biomimetic foods. Konjac gum only forms a gel under alkaline conditions or in large quantities, and the gel structure is soft, easily dehydrated, and shrinks. Studies have shown that a blending ratio of 70:30 for xanthan gum and konjac flour, with a total polysaccharide concentration of 1%, achieves the maximum synergistic interaction. Gel strength increases with increasing polymer concentration and decreases with increasing salt concentration. The blending of konjac gum and xanthan gum significantly improves the application performance of konjac gum, reduces dosage, and can be used as a thickener and gelling agent, widely applied in both food and non-food industries.
Blending of Xanthan Gum and Sophora Bean Gum
SopHora bean gum is a polysaccharide gum extracted from the endosperm of the seeds of the perennial leguminous plant Sophora japonica, with galactomannan as its main component. Studies have shown that a gel can be formed when the weight ratio of sophora bean gum to xanthan gum is 2:8 and the concentration reaches 0.5%~0.6%. The viscosity of the blended gum increases with increasing concentration; the blended gum is a “non-Newtonian fluid,” and the viscosity of the solution decreases with increasing shear force. Studies have also shown that heating time, heating temperature, pH, and freeze-thaw cycles all affect the viscosity of the compounded adhesive. The viscosity of the compounded adhesive tends to reach its maximum after heating for 60 minutes, while heating beyond 90 minutes causes a decrease in viscosity. Heating temperature also has a significant impact on the viscosity of the compounded adhesive; as the temperature increases, the viscosity increases considerably, with the optimal heating temperature being 60℃. Heating above 60℃ causes a decrease in viscosity. pH has a certain influence on the viscosity of the compounded adhesive, with a greater decrease in viscosity under alkaline conditions. Freeze-thaw cycles cause a significant increase in the viscosity of the compounded adhesive of locust bean gum and xanthan gum, with freezing causing the largest increase. Therefore, it can be applied to acidic frozen drinks, neutral acidic dairy beverages, plant protein beverages, and frozen and quick-frozen products, and can be flexibly applied in practice according to different needs.
Blending of Xanthan Gum and Guar Gum
Properties of Guar Gum: Guar gum is acid and alkali resistant, has high viscosity even at low concentrations, and good water retention, but it is easily decomposed and precipitated. It can be used as a thickener, emulsifier, film-forming agent, shaping agent, and stabilizer, and is often the first choice in noodle products and cold drinks.
Blending of the two: The distribution of galactose in the guar gum molecule is random and irregular. Some regions of its main chain lack galactose, while others have a higher distribution. Especially under very low ionic strength, the unbranched regions can form polymers with xanthan gum, producing a weak viscosity-enhancing effect. The blend of the two cannot form a gel, possibly because the main chain regions without galactose distribution are relatively small and cannot firmly interlock with the double helix structure of xanthan gum.
Compounding of Xanthan Gum and Gum Arabic
Properties of Gum Arabic: Gum Arabic is a weakly acidic, water-soluble macromolecular polysaccharide containing various cations such as calcium, magnesium, and potassium, isolated from the secretions of the arabic tree. Gum Arabic aqueous solution has the lowest viscosity, reaching its maximum viscosity at pH 6-7, and is commonly used as an ideal foam stabilizer in the beer industry. Gum Arabic is compatible with high sugar content, preventing the formation of “white bloom” on the surface of sucrose crystals, and is widely used in foods with high sugar and low water content, such as soft candies, sweets, and fruit cakes. The compounding of xanthan gum and gum arabic is not commonly used in the food industry. The two are often used as emulsifiers in flavorings, and can also be spray-dried to obtain solid flavorings, avoiding the volatilization and oxidation of flavorings. They can also be compounded with other food gums in high-protein dairy beverages.
Blending of Xanthan Gum and Gellan Gum
Gellan gum is a microbial polysaccharide, safe and non-toxic, with unique physicochemical properties. It is one of the most promising microbial polysaccharides in recent years. The monosaccharide composition of gellan gum is glucose, rhamnose, and glucuronic acid.
Properties of Gellan Gum: Gellan gum is not easily soluble in cold water. When a hot gellan gum aqueous solution cools, it forms a thermally reversible gel. The gel has good stability, is heat-resistant, and resists the action of microorganisms and enzymes; it has strong acid resistance, with the best performance under pH conditions of 4.0~7.5. Gellan gum is superior to colloids such as agar in terms of transparency and strength. Blending xanthan gum and gellan gum can arbitrarily transform the tissue structure from a brittle colloid to an elastic colloid. Gellan gum has excellent suspension properties and can be blended with xanthan gum for use in suspended beverages and liquid foods.
Blending of Xanthan Gum and Agar
Agar is a polysaccharide extracted from seaweed and is one of the most widely used alginates in the world. Agar, when used in food, can significantly alter its quality and enhance its grade.
Its characteristics include: gelling properties, stability, and the ability to form complexes with certain substances. It can be used as a thickener, coagulant, suspending agent, emulsifier, preservative, and stabilizer, and is widely used in the manufacture of orange juice with pulp, various beverages, jellies, ice cream, pastries, soft candies, canned goods, meat products, eight-treasure porridge, bird’s nest soup, stews, and cold dishes. Agar also has applications in the chemical industry and medical research, serving as a culture medium, ointment base, and other uses. Xanthan gum and agar have similar double-helix structures; a small amount of xanthan gum molecules can form a three-dimensional network structure with agar molecules. However, excessive use will inhibit cross-linking between agar molecules, reducing gel strength.
Blending of Xanthan Gum with Various Food Gums
Xanthan gum can be blended not only with single thickeners and gelling agents, but also with two or more types of thickeners and gelling agents, as well as other types of additives. Different food stabilizers and thickeners can be selected and blended in different amounts according to different production needs. Studies have shown that a blend of xanthan gum, guar gum, and locust bean gum has excellent effects in dairy products, with the best salt tolerance, lowest dosage, and lowest cost achieved at concentrations of 0.2%, 0.01%, and 0.9%, respectively. Another study showed that a blend of xanthan gum, konjac gum, and guar gum at concentrations of 0.3%, 0.01%, and 0.8% exhibits the best salt tolerance, lowest dosage, and lowest cost. Research indicates that in the improvement of dough products, blends of 0.5% xanthan gum, 0.08% CMC, and 0.04% carrageenan, and blends of 0.06% xanthan gum, 0.45% carrageenan, and 0.35% guar gum significantly improve the overall quality of frozen dough. Studies have also shown that a coating material made from 0.08% xanthan gum, 0.1% sodium alginate, and 0.09% chitosan has a significant effect on the preservation and storage of fresh-cut lotus root.
Outlook
Xanthan gum has excellent compounding properties. It can be used in combination with many food thickeners and gelling agents, as well as with other different types of food ingredients and additives, making the variety and serialization of food additives more refined. This will enable the development of more types of food to meet people’s growing demands for sensory and nutritional benefits. As a safe, stable, and compatible food additive, xanthan gum has a promising future. The content of food additives is “very rich,” and we still need to develop new and safe compound food additives in a more rational and scientific manner.
