X is for Xanthan Gum

Xanthan not only comes in handy for playing Scrabble (racking up a respectable 17 points without any bonus squares), it’s a great tool for developing products from a ready-to-use adobo sauce that clings to a chicken breast to a freeze/thaw stable zabaglione. Xanthan gum’s unique rheological and gel-forming properties make it a valuable ingredient.

Function follows form 

This high-molecular-weight polysaccharide results from carbohydrate fermentation by a naturally occurring bacterium, Xanthomonas campestris. Different strains or fermentation conditions create differing degrees of acetylation and pyruvylation, which affects functionality.

Like all gums, its structure dictates functionality. The molecule has a helical form, with a backbone of ß-1, 4-linked D-glucose residues. Side chains containing one glucuronic acid unit between two mannose units are linked to every other glucose unit. These side chains provide some protection to the molecule, so it is relatively stable to acids, alkalis and enzymes. The number of side units per unit length of the monosaccharide chain affects solubility. Increasing substitution holds the chains apart from each other and prevents them from forming hydrogen bonds, so, as is the case with xanthan gum, they hydrate more quickly.

One of the reasons for xanthan’s value to the food industry is its versatility: It’s cold-water and hot-water soluble. Plus, according to Aida Prenzno, laboratory director, Gum Technology Corporation, Tucson, AZ: “Xanthan gum is stable in a wide range of pH. It can be used in a pH range from 2 to 10 where its viscosity, texture and functionality are not affected.” Plus, it will dissolve in highly acidic solutions, as well as those with a high pH. At low concentrations, xanthan-gum solutions provide a high degree of viscosity compared to other polysaccharide solutions. The viscosity remains virtually unchanged in temperatures from freezing to boiling. Xanthan is also stable in the presence of most salts. Adding electrolytes, such as sodium and potassium chloride, increases viscosity and stability, and calcium or magnesium salts also increase viscosity. Salt concentrations above 0.1% provide optimum viscosity.

The gum is highly pseudoplastic (shear-thinning), allowing it to be blended easily during mixing, and pumped or poured easily once the yield value (the initial force to initiate flow) is reached. When shear is removed, it goes back to its original viscosity. The same rheology contributes to good mouthfeel and flavor release. Xanthan provides 0.6 kcal per gram, making it suitable for fat-replacement systems.

Xanthan can even provide some emulsification. “Xanthan provides viscosity, suspension and keeps the emulsion together,” says Prenzno. “Although xanthan is not a true emulsifier, it can be used to replace expensive products such as tragacanth in highoil- content dressings if it is used in conjunction with gum arabic or propylene glycol alginate.”

Energizing synergy 

One of xanthan’s unique properties is synergism with certain other gums. Synergism occurs when the viscosity or gel strength of a hydrocolloid combination is greater than would be predicted by adding the properties of the individual ingredients. Xanthan, konjac and ê-carrageenan or xanthan and guar show viscosity synergies. Xanthan and locust bean gum (LBG) form a synergistic gel (a molecular network due to chemical bonding or crosslinking), and at levels upwards of 0.2%, solutions of xanthan gum and LBG form a thermally reversible gel when heated to 85°C and higher, and then cooled. The greatest gel strength occurs at a 50:50 ratio of xanthan gum to LBG, but can be influenced by the product matrix.

“Xanthan gum is synergistic with galactomannans, because their backbone structure is similar, and there is an electrostatic attraction between the molecules,” explains Yvonne M. Stuchell, senior research food scientist, specialty food ingredients division, ADM, Decatur, IL. “Galactomannans with fewer galactose side chains and more unsubstituted regions will react more strongly with xanthan gum than those with higher levels of side chains and more evenly substituted regions. This interaction is strongest in distilled water, and may be inhibited by ions and acidic conditions in foods.” The synergistic interactions are best-suited to products with higher pH and lower salt levels, and those with a shorter shelf life, she says.

Application whiz 

As with most gums, proper dispersion of xanthan is key. A high-shear mix is a must to prevent lumps, due to the rapid hydration rate. Preblending with dry ingredients or suspending it in oil or alcohol aids hydration by separating the particles.

Using an agglomerated version aids dispersal. Agglomeration “changes the solubility and hydration characteristics,” says Frances Bowman, marketing manager, TIC Gums, Inc., Belcamp, MD. “Agglomerating the xanthan separates the gum particles and makes them easier to disperse. This creates more surface area to come into contact with the water and dramatically improves hydration rates, which can help speed up processing times. In the finished application, agglomerated xanthan gum provides the same functionality as powdered xanthan.”

Once the gum has been dispersed, it’s ready to stabilize any number of foods and beverages, from meats to baked goods to sauces, and many more. “Typical xanthan gum use levels in most foods are below 0.75%, and usually between 0.10% and 0.40%,” says Stuchell.

“Salad dressing is the application that first comes to mind when you mention xanthan gum, because it’s frequently used to thicken the dressing and suspend spices and other particulates,” says Bowman. Depending on the formulation, 0.1% to 0.5% results in a salad dressing that balances easy pourability and good cling.

Baked goods tend to require a low use level, approximately 0.02% to 0.10%, according to Stuchell, “because blends of ingredients are usually used, and products can become too gummy if the use level is high.” In beverages, often less than 0.10% xanthan is required, or else the mouthfeel becomes too thick.

“In most foods, using too much xanthan gum results in unacceptable flow behavior— gloppy or stringy,” and a mouthfeel that’s too slippery or slick, Stuchell warns. However, the right level is priceless for just about any application that requires smooth body and viscosity, freeze/thaw and emulsion stability, and syneresis control.