Many polysaccharides from plants, seaweed, carrageenans, and microorganisms are used as natural or modified food additives. Xanthan gum, also called corn sugar gum, is an example of polysaccharides produced from microorganisms. It is produced by aerobic fermentation of Xanthomonas campestris, a bacterium found on the leaves of the Brasica vegetables like cabbage. Xanthan gum and the majority of its substitutes are hydrocolloids. Hydrocolloids serve as gelling agents, thickeners, fat replacement agents, fiber sources, emulsion stabilizers, suspending agents, emulsion stabilizers, and processing aids.

Bacterial gums have properties that are also useful in pharmaceutical, and other similar fields.

Xanthan gum was discovered by a team of researcher at the United States Department of Agriculture (USDA) in 1963. And commercialization started during the late 1960s. In 1968, it was approved for use as a safe ingredient in food. Today, xanthan gum is a very common ingredient in food.

It is used in a wide range of food products such as salad dressings, sauces, instant soups, canned foods, and dairy products. The pH range of a solution containing 1% xanthan gum is 6.1 to 8.1. And solutions act like a complicated web of intertwined rod-shaped molecules.

Health-wise, xanthan gum is a popular option for people who love consuming baked products. It does not contain gluten or carbohydrates. Hence, it is a keto and gluten-friendly option in breads and other baked goods.

In this post, we’ll discuss xanthan gum in detail, including its composition, manufacturing process, functions in food, as well as its substitutes.

XANTHAN GUM CHEMISTRY

Xanthan is widely used as a food gum because of its characteristics. It is soluble and very stable in acidic and alkaline systems (pH 2 to 12). It readily dissolves and hot and cold water. Even at low concentrations, its dispersions are highly viscous. Temperature has a strong influence on viscosity. But there is no discernible change in solution viscosity between 23°F (0°C) and 212°F (100°C), making xanthan gum unique among food gums. The thermal stability of xanthan gum makes it an ideal thickener in canning.

The pseudoplastic thixotropic property of xanthan gum is due to the intermolecular association of single-stranded molecules. This is useful in the production of salad dressings.

Xanthan gum is an anionic polysaccharide. It is composed of D-glucose, D-mannose, and D-glucuronic acid monomers. Similar to cellulose, the polymer backbone consists of (1 ->4)-linked β-D-glucose units.

A trisaccharide chain with one glucuronic acid and two mannose residues is fixed to the 3-position on alternate glucose units. Because of this, a stiff chain can be formed that can have one, two, or three helixes.

The molecular weight is roughly 2 x l06. Unlike most polysaccharides, xanthan has a narrower molecular weight distribution. The degree of substitution in the structure may also change. This depends on the bacterial strain used in the production.

Unquestionably, the highly beneficial properties of xanthan are caused by the rigidity and extended nature of its molecules, which in turn are caused by its linear cellulosic backbone, which is stiffened and protected by the anionic trisaccharide side chains.

FUNCTIONS OF XANTHAN GUM IN FOOD

In many starchy food systems, adding 0.05-0.5% xanthan gum reduces the amount of starch required while improving rheology and stability. For example, It thickens and adds viscosity to gluten-free breads and other baked goods. Without it, gluten-free breads would be dry, crumbly, and flat. Because it is gluten-free and vegan, xanthan gum is the preferred thickener for home bakers with food allergies.

Xanthan gum can be used alone for a specific function. But it is also frequently combined with other hydrocolloids, which are xanthan gum substitutes as well. For example, if the viscosity of the dispersion needs to be raised, xanthan gum and guar gum can be combined. This is especially useful for food products that require a consistent viscosity across a wide pH, salt concentration, and temperature range.

Another reason is that xanthan gum normally works as a thickener, but does not form a thermoreversible gels. It does in the presence of another polysaccharide like locust bean gum, carrageenan, or konjak gum. The interaction of xanthan molecules with the unbranched part of another polysaccharide molecule with its binding zone is required for gel formation. Deacetylated xanthan produces more elastic, cohesive gels.

In comparison to other hydrocolloids, xanthan gum is relatively inexpensive. And its extreme versatility makes it present in most thickened products. In fact, most salad dressings on the market contain xanthan gum in combination with propylene glycol alginate (PGA). PGA helps reduce the viscosity and pseudoplasticity of the xanthan-containing system. Together, they provide the desired pourability of pseudoplastic xanthan and the creamy sensation of a non-pseudoplastic solution.

At home, a pinch of xanthan gum to a mayonnaise or hollandaise can effectively stabilize the emulsion system, making it difficult to separate. Xanthan gum also acts as a “pseudo plasticizer” to help them pour smoothly.

HOW XANTHAN GUM IS MADE

There are two main categories of polysaccharides that specific microorganisms and higher fungi produce: extracellular and intracellular. Bacterial extracellular polysaccharides build up as capsule-like structures. These capsules diffuse into the growth medium while still remaining a part of the cell wall or as an amorphous mucilaginous substance surrounding the outer cell wall. These mucilages, also known as bacterial gums, serve to prevent dehydration, fix microorganisms to the environment, and shield cells from bacterial viruses (bacteriophages). Xanthan gum is the most significant bacterial extracellular hydrocolloid utilized in food.

To produce xathan gum through aerobic fermentation of Xanthomonas campestris, a carefully chosen culture is grown on a carbohydrate-containing nutrient medium containing a nitrogen source and other necessary elements. Fermentation takes place at 86°F (30°C). When the fermentation is finished, the broth is sterilized to remove any viable microorganisms. Centrifugation is used to remove extracellular components. Variables such as pH, temperature, and aeration are carefully controlled. The resulting product is sterile. After 1 to 4 days, the gum precipitates after the addition of isopropyl alcohol. Following washing, the precipitate is pressed to remove any remaining alcohol before being dried and ground to the desired size.

XANTHAN GUM SUBSTITUTES

There are a few widely used substitutes for xanthan gum, and you can typically find them at most grocery store. These xanthan gum substitutes include locust bean gum, guar gum, gelatin, gum arabic, carrageenan, agar, cornstarch, and sodium carboxymethyl cellulose. Like xanthan gum, they have various applications in food.

Locust bean gum

Locust bean gum is not made from locust! It is actually a vegan product made from seed of the locust bean tree (carob tree), hence the name.

Locust bean gum can be used alone as a thickener. It dissolves in water at 176°F (80°C). It is mainly used as a stabilizer in processed meat and dairy products. When combined with carrageenan, the two substances work synergistically to create a gel that is elastic and incredibly cohesive. Although locust bean gum is generally too viscous on its own to be much used in confectionery, it is used to stiffen agar jellies. After reconstitution in water, a mixture of locust bean flour, Na-pyrophosphate, milk powder, xanthan gum produces instant jelly.

It is used in ice cream as a thickener at concentrations of 0.1-0.2%. Heating to around (176°F) 80°C for 30 minutes is necessary to achieve full viscosity.

Guar gum

Guar gum is a vegetable gum made from the seeds of Cyamopsis tetragonoZopus. It originated from Pakistan and India. Guar gum is the most viscous of any natural commercial gum. Guar gum thickens a variety of food products at a low cost. It is used as a thickener for hot and cold beverages, as a stabilizer for frozen fruits, glazes, and icing, and as a binder for confections, meats, and baked goods.

It is frequently combined with other food gums, such as in ice cream, where it is frequently combined with carboxymethylcellulose, carrageenan, and locust bean gum to benefit from the synergistic gel-forming phenomenon. The usual use ranges from 0.05% to 0.25%..

When replacing xathan gum with guar gum, use 3 parts of it for every 2 parts of xanthan gum.

Gelatin

Gelatin is a flavorless protein prepared from the tenderization of collagen obtained from animal sources. Cold water is absorbed by it five to ten times its weight. Gelatin is a highly versatile ingredient. It is primarily used as a gelling agent in various dishes and desserts. It is also used as a thickener and stabilizer in baking and cooking, as well as a base for puddings, fruit gelatins, and sausage casings. Lard can also be made from the raw material.

It is made on a large scale from animal bones or skin that has been treated with alkali or acid and then extracted with water.

Products with various molecular weights and, consequently, gelling characteristics are produced depending on the process. Some brands are used as food gelatins, while others are crucial to other industry (making film emulsions, glue).

To substitute gelatin, use 2 parts gelatin for 1 part xanthan gum.

Gum Arabic

The dried exudate of the acacia tree is known as gum Arabic. Exudates are gums that are released or exuded in response to plant tissue damage. When exposed to air, they produce highly tough, shiny nodules or flakes that can be harvested.

Gum arabic is a cold-water soluble gum that is used to stabilize emulsions and control crystal size in ices and glazes. Gum tragacanth produces very viscous sols and is used to give food products a creamy texture. It is also utilized to suspend particles and as a stabilizer in salad dressings, ice cream, and confections.

Sweetened, acidified, colored carbonated purified water is used to make modern cola drinks. They also have a compounded flavor mix that includes caffeine, cinnamon, citrus and vanilla, and gum Arabic as an emulsion stabilizer.

In baking, It is primarily used to make baked products rise, stabilize product texture, and increase the viscosity of liquids.

For more on gum Arabic, check out this post: Gum Arabic And Its Uses In Food (E414)

Carrageenan

Carrageenan is derived from red seaweeds, particularly Irish moss. It is found in three major fractions: kappa-, iota-, and lambda-carrageenan. Each is a galactose polymer in varying concentrations of negatively charged sulfate esters. Kappa-carrageenan contains the fewest sulfate ester. It is the least negatively charged. With potassium ions, it can form strong gels. Lambda-carrageenan has the most sulfate groups and is too highly charged to form a gel. With calcium ions, iota-carrageenan forms gels.

Carrageenans are added to milk products such as canned evaporated milk, ice cream, chocolate milk, and processed cheese to help them stay stable. Their ability to interact with proteins allows them to function extremely well. Because of their ability to cross-link with other gums, carrageenans can also be used with them.

Agar

Agar is derived from the red algae Rhodophyceae. It dissolves in boiling water, but not in cold water. The gels it form are heat resistant. Like xanthan gum, agar is commonly used in food as an emulsifying, gelling, and stabilizing agent. Agar is also used as a vegetarian substitute for gelatin, which is made from red algae or seaweed, despite the fact that the two have very different mouthfeels and textures.

Agar is used to make agar jellies. A jelly texture can be achieved with a very low concentration of agar (0.2%). However, acids are required to provide firmness.

Agar’s gel formation properties are unique. The gels are notable for being strong, transparent, and heat-reversible. This means they melt when heated and reform when cooled. Agarose and agaropectin are the two fractions found in agar. At high temperatures, agarose exists in a disordered “random coil” form, but when cooled, it forms unique turbid, brittle gels at concentrations as low as 0.04%.

Its work similarly to xanthan gum and gelatin in terms of yield, but is a bit dense. It is also gluten-free and keto-friendly.

Cornstarch

Cornstarch is a common thickener in soups and gravies. When proteins cool, they coagulate, whereas gums and starches thicken more effectively. When reheated, starch thickeners quickly clump.

Starch and xanthan gum both work well in viscous preparations. If a clear, thick soup is desired, a small amount of xanthan gum can be used to prevent clumping and cloudiness. However, pH can have an effect on the behavior of a thickening agent. Because acidic foods make some gums less effective, cornstarch is a better choice. Clear Jel is a chemically modified cornstarch that is specifically designed for baking and freezing acidic foods; it is an excellent choice for thickening acidic fruit pies.

Cornstarch can easily be substituted with xanthan gum in a 1:1 ratio.

Sodium carboxymethyl cellulose

The polycarboxymethyl ester of cellulose is known as sodium carboxymethyl cellulose (CMC). It is one of the gums most frequently used in food production due to its low cost. Commercial CMC, also referred to as cellulose gum, is available in various viscosity grades. Since it is inexpensive and comes in a wide range of viscosities, manufacturers can use it in a variety of foods that call for higher viscosity even though it does not gel.

Its applications in food include beverages, dressings, baked goods, extruded foods, sauces, and frozen desserts.

References:

W. P. Edwards (2000). The Science of Sugar Confectionery. The Royal Society of Chemistry.

S. Damodaran, K. Parkin (2017). Fennema’s Food Chemistry (5th edition). CRC Press.

J. Valisek (2014). The Chemistry of Food. John Wiley & Sons, Ltd

J. deMan, J. Finley, W. Jeffrey Hurst, C. Y. Lee (2018). Principles of Food Chemistry (4th edition). Springer

M. Gibson (2018). Food Science And The Culinary Arts. Academic Press.

P. Cheung, B. Mehta (2015). Handbook of Food Chemistry. Springer

M. Wallert, K. Colabroy, B. Kelly, J. Provost (2016). The Science of Cooking: Understanding The Biology And Chemistry Behind Food And Cooking. John Wiley & Sons, Inc..

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