Due to its good rheological characteristics, gellan gum is a bacterial polysaccharide with great commercial potential for food, pharmaceuticals, and particularly environmental bioremediation. There are reports that gellan gum can be used in the bioremediation of contaminated soils and aquifers41- 44.
Applications in food industry :
Gellan gum is a food additive that functions as a stabilizer, thickening agent, structuring and versatile gelling agent in a wide variety of foods and can produce gel textures in food products ranging from hard and brittle to fluid. Types of food products that typically contain gellan gum include: bakery fillings, confections, dairy products, dessert gels, frostings, icings and glazes, jams and jellies, low-fat spreads, microwavable foods, puddings, sauces, structured foods, and toppings47.
Water-based dessert gels48 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. Gellan gum can be used wholly or partly in place of gelatin to improve the characteristics of the aspic.
In fruit-based products49, 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.
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.
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.
Gellan gum also may be used in canned cat and dog food.
Applications in personal care:
In cosmetic applications, gellan gum can be used in lotions and creams, make-up, face masks and packs, hair care products, toothpaste, and air freshener gels and 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.
Applications in Pharmaceutical Industry:
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. Gellan gum is also conveniently used for controlled or sustained release of various drugs (54- 58) and also for microencapsulation preparation59. The bioavailability of theophilline from the gellan gels increases 4-5 folds in rats and 3 folds in rabbits compared to a commercial sustained release liquid dosage form6.
Applications in biotechnology Industry:
Gellan gum can be used as an alternative to agar for microbiological media11, 46, and as a bacterial growth media51, 52. It is also ideal medium for plant tissue cultivation23, 53. 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.
It is extremely effective at low use levels and forms solid gels at concentrations as low as 0.1%. These are prepared by adding an electrolyte (e.g., a salt, an acid or an anionic surfactant) to a hot gellan solution and then cooling. Air freshener gels are transparent, have a high melting temperature and may contain high levels of fragrance.
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.
Detailed description of gellan gum products in various fields:
1) Starch-based products (fruit fillings, etc.)
This product contributes to increase of stability of starch paste, improvement of structural quality, and reduction of the amount of starch required. If left after pasting, the paste's property of partially restoring the structure and improvement of structural quality will allow the fillings to suck up water, resulting in rapid baking effect. This advantage can be applied in making the pie, pastry, and dual-pie.
2) Gel products (Dessert gel, etc.)
With only the gellan gum or combination with other conventional gelatin component, various products with heat stability and excellent emanation of odor can be manufactured. Further, use of the gellan gum will increase the setting temperature, which enables easy setting without refrigeration. If the gellan gum is added to a product with tendency of being melted when exposed to high temperature in the course of distribution and storage, heat stability of the product can be greatly improved.
3) Beverage
Gellan gum as fluid gel - Gellan gum can be used as a unique suspending agent. Gels occur when hot gellan gum solutions are allowed to cool and set under quiescent conditions. However, with low concentrations of gellan gum, shearing the gel results in the formation of pourable fluid masses with very short, flowable texture. These systems, commonly known as fluid gels, can have a wide range of textures and can exist as a light pourable gel or a thick, spreadable paste.
Gellan gum fluid gels have a high low-shear viscosity, providing remarkable suspending properties at low gum concentrations. With highly pseudoplastic, or shear thinning flow properties, application of an external shear reduces the apparent viscosity significantly. Fluid gels made from gellan gum also have a true yield stress, which imparts excellent suspension properties22.
With employment of the fluid gel technology, various beverage products can be stabilized. Small amount of the gellan gum (0.04∼0.3%) is required for preparation of the fluid gel and maintenance of the suspension status with excellent low-viscosity. Further, the gellan gum improves the feeling when drinking an orange beverage, prevents settlement of dietary fiber, and enables production of transparent beverage products. The fluid gels, which are filled at high temperature and cooled down so as to form very fragile gels, can be broken if the bottle is shaken. Such fluid gels can be used in the manufacture of the lemonade, chocolate milk, fruit juice beverage, juice, soft drink, low-fat/fat-free dressing, sauce, fermented milk, ice cream, and topping.
In addition, beads with various colors and flavors can be prepared and used in the manufacture of beverage. To prepare such beads, the gellan gum solution is dropped into an ion-rich flavor system (diffusion setting method). Carbonated beads also can be made by adding calcium carbonate into the gellan gum solution and dropping the solution into citric acid solution or fruit juice. The acidic juice will promote the gelation process and dissolve calcium carbonate to generate carbon dioxide, which is positioned inside the beads.
4) Dairy products
If the gellan gum is added to milk, and then heated and cooled down, the gellan gum makes the gel of unique structure. In manufacture of various dairy products, such as ice cream and yoghurt, the gellan gum acts as a stabilizer to help formation of gel. The gellan gum's heat stability and low viscosity at high temperature are useful in manufacturing a product going through heat treatment, such as UHT or HTST.
5) Adhesion systems
Use of the gellan gum enables easy preparation of fat-free adhesion system. If the gellan gum solution is sprayed on various foods, such as the cracker, cookie, pretzel, potato chip, and rice cake, and then various seasoning flavors and other materials required for adhesion are sprinkled, a product with greatly reduced fat concentration can be manufactured.
6) Jam/Jelly (Low sugar jam, jelly, etc.)
Since high methoxyl pectin requires careful adjustment of pH and high concentration of sugar, it cannot be used for manufacture of low solid contents products. Also, low methoxyl pectin or kappa-carrageenan causes various problems relating to storage and stability. However, the gellan gum provides stability during processing and storage, and use of only small amount results in gels with excellent taste and appearance.
7) Film and coating
The gellan gum can be used for preparation of useful films or coating in the course of making batter or breading of chicken, fish, cheese, potato, egg roll, and pizza roll. The films can be formed by spraying the hot solution of gellan gum on the surface of food, immersing the food in such hot solution of gellan gum and then cooling it down, or immersing the food in the cold solution of gellan gum. Such film formed makes a membrane that reduces oil absorption, enabling longer maintenance of crunch structure after oil-frying or baking.
Breading can be performed by spraying the gellan gum solution or immersing in the solution and then slight frying or freezing. If the foods with such breading are heated in a microwave range or an oven, they appear to be freshly fried in oil, producing low-oil foods.
Conclusion:
The large variety of applications as well as the steadily increasing number of research workers engaged in studies of Gellan gum due to their unique properties, have made significant contributions to many types of formulations and suggest that the potential of Gellan gum as novel and versatile will be even more significant in future.
