Gellan Gum Description
Gellan is a high molecular weight polysaccharide produced by the micro-organism Pseudomonas elodea. This organism was found during an extensive screening programme seeking naturally occurring hydrocolloids with useful properties. Gellan gum is a multi-functional gelling agent that can produce a wide variety of interesting textures. It is extremely effective at low use levels and is available in two forms. High acyl gellan gum forms soft, elastic gels. Low acyl gellan gum forms firm, brittle gels.
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Gellan gum, which forms gels on cooling, is a versatile and effective gelling agent. It is available in two forms (high or low acyl content). The acyl groups have a profound influence on gel characteristics. The high acyl form produces soft elastic gels, while the low acyl form produces firm brittle gels. They may be used alone or blended to give products with the desired characteristics.
A further benefit of gellan gum is that it can be used at very low concentrations to produce products with excellent flavour release and no flavour masking.
In most practical situations, gels made with low acyl gellan gum are not thermally reversible and will be retort or bake stable.
Gellan gum can form fluid gels, which are in effect solutions with a weak gel structure. They exhibit an apparent yield stress, ie a finite stress which must be exceeded before the system will flow. Their highly pseudoplastic flow properties provide extremely efficient suspension combined with low viscosity at higher shear rates. This results in low viscosity in the mouth, making them particularly effective in suspending a wide variety of solids and emulsified oils. Suspension can be achieved without affecting the mouthfeel.
Gentle agitation of a weak gellan gum after it has set is also sufficient to form a weak, pourable fluid gel. This means fluid gels can be formed using standard filling operations.
Extensive investigations with respect to toxicology and safety have shown that gellan gum is a safe food additive. It was cleared by the FDA (the US Food and Drug Administration) in 1969 and registered in the Code of federal Regulations.
Gellan gum is approved as a food additive in the European Community under the number E 418, with ADI (acceptable daily intake) “not specified” confirming its status as a safe food additive. The gellan gum food grade produced by Biopolymer members fully meets the standards and the purity criteria issued in different regions of the world or internationally, such as the Food Chemicals Codex and JECFA, the US Pharmacopoeia/National Formulary, and the European Directives.
Due to the extraordinary properties as stabiliser and thickener gellan gum is used in the food, cosmetic, pharmaceutical and also in various industrial applications.
Gellan gum functions as a structuring and gelling agent in a wide variety of foods. Typical examples are shown below. Although gellan gum can be used alone effectively in many products, its benefits are sometimes better realised in combination with other hydrocolloids.
Water-based dessert gels are popular throughout the world and have a range of textures. Gellan gum can furnish textural diversity in these products coupled with outstanding flavour release. Small amounts of gellan gum can be used in gelatin desserts to improve heat stability and raise the setting temperature so gels will set without refrigeration. Gellan gum also improves the heat stability of other gelled products prone to melting when exposed to high ambient temperatures.
Savoury gels or aspics sometimes are used in specialty meat, fish and vegetable products to provide added appeal and succulence. Gelatin usually is the gelling agent of choice. Again, gellan gum can be used wholly or partly in place of gelatin to improve the characteristics of the aspic.
In fruit-based products, gellan gum offers robustness during processing, provides good product stability during transportation and storage, and through its characteristic gel texture and low-concentration requirement, creates products with excellent taste and appearance.
In fruit fillings for bakery products, use of gellan gum can provide additional structure and reduction of starch levels. The added structure, coupled with the ability of the pastes to partially recover structure after shearing and depositing, results in fillings that retain water and show good bakefastness.
Since high solids products such as gelled confections are made by heating and cooling, gellan gum often can be used in their manufacture without process modifications. By using gellan gum in combination with the appropriate starch, it is possible to reduce the set time of starch jellies so they can be removed more quickly from the starch moulds. Gellan gum can also be used to impart increased heat stability to gelatin confections, resulting in products that store better at high ambient temperatures.
In decorative icings, frostings and glazes for baked goods, benefits obtained from gellan gum include good shelf stability, moisture retention, spreadability, sheen, texture and flavour release.
Gellan gum can provide added benefits to beverages by use of fluid gel technology. Gellan gum fluid gels are solutions with a weak gel structure that provide good suspension at low viscosity.
On heating and cooling in milk, gellan gum produces a delicately textured gel which can be beneficial in dairy products such as creme brulees and yoghurts.
In South East Asia, texture is a very important characteristic and desirable texture is as important as flavour. Drinking jellies are very popular and gellan gum fluid gel technology is often used in these products.
Gellan gum forms films and coatings that offer several advantages, particularly their ability to reduce oil absorption in products such as breadings and batters for chicken, fish and vegetables.
The use of gellan gum in emulsions and cakes illustrates that it is not solely a gelling agent but can also be used in applications where structure and stability, rather than gel formation, are required.
In cosmetic applications gellan gum is frequently used as a structuring as well as a gelling agent, providing body, stability and pleasing skin feel.
Gellan gum can provide effective stabilisation and suspension of shampoo and conditioner formulas. It is ideally suited to products requiring a pseudoplastic (shear thinning) rheology. In creams and lotions, the high yield value of gellan gum fluid gels effectively stabilises these emulsions and imparts a ‘light and silky’ feel when rubbed on the skin. Gellan gum also keeps emulsions stable during temperature fluctuations, for consistent quality in transit, as well as on the shelf.
In suntans and sunscreens, gellan gum stabilises the oil phase and delivers the important ingredients to the skin in a uniform manner. Gellan gum offers excellent stability over the wide range of temperatures that these products experience.
In toothpaste formulations gellan gum is beneficial both for its binding properties and its reversible, non-stringy, true-gel structure. It provides excellent flavour release, so significant reductions of flavour and sweetener levels are possible. At typical use levels, gellan gum contributes very little viscosity during toothpaste preparation allowing the design of fluid formulations that subsequently form a gel after packaging. This low viscosity performance makes manufacturing and packaging easier and allows the incorporation of fragile ingredients such as encapsulated flavours that would not normally be possible with typical binder systems. Blends of low and high acyl gellan gum can produce toothpastes with a variety of binding, stand-up and preparation viscosity.
Gellan gum can be used to produce easy-to-swallow solid dosage forms, such as gels and coated tablets, and to modify the rate of release of active ingredients from tablets and capsules.
Other industrial applications:
Gellan gum can be used as an alternative to agar for microbiological media. It is particularly useful for the culture of thermophilic microorganisms, as the gels are thermostable and can withstand prolonged incubations at high temperatures.
In addition, acceptable gel strengths can be obtained using gellan gum at a lower level than agar, and spreader colonies do not become too large. In these microbiological media applications, the high purity of gellan gum and the water-like clarity of the gels are distinct additional advantages.
In plant tissue culture, gellan gum offers a promising alternative to agar because of its purity. Gellan gum used at one-fifth the agar use level, resists contamination by moulds, is easily washed from the plant tissue for transplanting, and allows clear observation of root and tissue development.
In air fresheners, gellan gum enables air freshener gels of crystal clarity to be formulated. The high melting temperature of these gels makes them suitable for use in hot environments, such as cars.