Gellan Gum-Food Stabilizer, Thickener and Gelling Agent

Abstract

Food stabilisers, thickeners and gelling agents(Gellan Gum)are obtained from a wide range of natural raw materials including microorganisms, land and sea plants and animal connective tissues.

They control moisture and provide structure, flow, stability and eating qualities to food products. Approvals for food use and purity criteria are closely controlled by regulation.

Commercial applications are determined by the combination of properties provided by these materials including the current significant market drivers of price and availability coupled with consumer and retailer preferences. Future developments with hydrocolloids will recognise the value of nutritional and therapeutic benefits in addition to the functional attributes.

Within the food industry, stabilisers, thickeners and gelling agents are often more simply referred to as food hydrocolloids. The hydrocolloids traditionally used in food thickening and gelling include, but are not limited to, the following: agar, alginates, arabic,
carrageenan, cassia tora, carboxymethyl cellulose, gelatin, gellan, guar, karaya, konjac, locust bean gum, methyl cellulose, hydroxypropylmethyl cellulose, microcrystalline cellulose, pectin, starches, tara, tragacanth and xanthan.

Definition

All the stabilisers, thickeners and gelling agents listed above are also known and
described as ‘food hydrocolloids’ implying that functional properties are obtained by mixing
them with water. A strict definition of a hydrocolloid is, however, difficult. Ask ten scientists
what is a hydrocolloid and it is likely that ten different answers will be obtained. These could
include statements as follows:

A colloidal substance obtained from ...
A material that hydrates in water ...
A colloid forming a suspension and not a true solution in water ...
A synonym for gum (e.g. guar gum, locust bean gum, gum arabic ...)
A macromolecule, such as a carbohydrate polymer or a protein, that is water soluble ...

Many of these ingredients are carbohydrates but at least one important hydrocolloid, gelatin, is a protein. Most are agricultural derivatives but some are biotechnology derived, and gelatin, of course, is an animal product. This volume presents some scientific information but focuses more on the ‘real world’ of application-related data that will be of most benefit to food technologists and food formulators.

Functional Properties

The following is a brief overview of the key functional properties for which these ingredients
are used. Nutritional properties are relatively new and nutraceutical or health-enhancing
properties are even more recent. Further work is sure to advance the use of hydrocolloids
beyond modification of the rheology of foods.

Viscosity

Viscosity is probably one of the most widely used properties. In this respect, hydrocolloids
are often used in systems where the oil or fat content has been reduced or eliminated through substitution with water. The hydrocolloid thickens water, which, in turn, replaces the fat or oil to give a product with similar properties to the full-fat food. A typical application for this function is reduced-fat salad dressings. In other cases, the thickened water simply adds body, texture and mouthfeel to a food such as table syrups, particularly low-calorie syrups.

Stability

If oil or fat is partially removed from a formulation and is replaced with thickened water, an
emulsion is usually formed. Often the function of the hydrocolloid is to stabilise the emulsion, to prevent separation and, in the case of frozen foods, to control ice crystal formation. New technology and new ingredients have been developed specifically to address the problem of ice crystals in frozen foods, but hydrocolloids will continue to play a role. Virtually every ice cream product sold in retail outlets is stabilised with carrageenan, locust bean gum and/or guar gum. Low-fat salad dressings, discussed above, also benefit from emulsion-stabilising properties.

Suspension

If insoluble particles are included in the thickened product then separation and settling should be eliminated or at least minimised. Some hydrocolloids create solutions with a ‘yield point’ that will keep particles immobilised in suspension. Salad dressing is a good example of this and Gellan gum is the typical hydrocolloid to supply this functionality.

Gelation

One of the key texturising aspects of hydrocolloids is the ability to gel and solidify fluid
products. For example, in gelled milk desserts, even low levels of carrageenan will form a
solid milk gel. Other classic gelling agents are pectin, gelatin and agar. Many others, however, will form a gel under specific conditions. Certain grades of alginates form gels with calcium ions. Xanthan and locust bean gum do not gel individually but together they display synergy and form a strong cohesive gel. Methyl cellulose and hydroxypropylmethyl cellulose are unusual in forming solutions that reversibly thicken or gel when heated. The food industry has a myriad of gelling applications ranging from soft, elastic gels to hard and brittle gels.

Nutritional and nutraceutical

There is already a wide use of some hydrocolloids, arabic and guar gum, for example, as
sources of soluble dietary fibre. Much research has been conducted in the nutraceutical
benefits of hydrocolloids. Potential benefits range from cholesterol reduction to cancer risk
prevention. Their use in weight loss programmes is already widespread and likely to expand
further.