Hydrocolloid Polymers and Gums

Hydrocolloids often called gums,a are hydrophilicb polymers, of vegetable, animal, microbial or synthetic origin, that generally contain many hydroxyl groups and may be polyelectrolytes. They are naturally present or added to control the functional properties of aqueous foodstuffs. Most important amongst these properties are viscosity (including thickening and gelling) and water binding but also significant are many others including emulsion stabilization, prevention of ice recrystallization and organoleptic properties. The degree with which the hydrocolloid solutions mix with saliva, determined by their degree of chain entanglement, determines flavor perception.

Other more specialist applications include adhesion, suspension, flocculation, foam stabilization and film formation. Foodstuffs are very complex materials and this together with the multifactorial functionality of the hydrocolloids has resulted in several different hydrocolloids being required; the most important of which are listed below.

Agar (Chime)
Alginate (Chime)
Arabinoxylan (Chime)
Carrageenan (Chime)
Carboxymethylcellulose (Chime)
Cellulose (Chime)
Curdlan (Chime)
Gelatin (Chime)
Gellan
β-Glucan (Chime)
Guar gum (Chime)
Gum arabic
Locust bean gum (Chime)
Pectin (Chime)
Starch (Chime)
Xanthan gum (Chime)

Each of these hydrocolloids consists of mixtures of similar, but not identical, molecules and different sources, methods of preparation, thermal processing and foodstuff environment (for example, salt content, pH and temperature) all affect the physical properties they exhibit. Descriptions of hydrocolloids often present idealized structures but it should be remembered that they are natural products (or derivatives) with structures determined by stochastic enzymic action, not laid down exactly by the genetic code. They are made up of mixtures of molecules with different molecular weights and no one molecule is likely to be conformationally identical or even structurally identical (cellulose excepted) to any other.

XANTHAN

Xanthan gum is a long chain polysacharide composed of the sugars glucose, mannose, and glucuronic acid. The backbone is similar to cellulose, with added sidechains of trisacharides (three sugars in a chain.A polysacharide is a chain of sugars. Some familiar polysacharides are starch and cellulose.

It is a slimy gel produced by the bacterium Xanthomonas campestris, which causes black rot on cruciferous vegetables such as cauliflower and broccoli. The slime protects the bacterium from viruses, and prevents it from drying out.

Xanthan gum is used as a thickener in sauces, as an agent in ice cream that prevents ice crystals from forming, and as a fat substitute that adds the "mouth feel" of fat without the calories. It is used in canned pet food to add "cling".

In pastry fillings, it prevents "weeping" (syneresis) of the water in the filling, protecting the crispness of the crust.It has a very high viscosity (thickness) even when very little is used.

When mixed with guar gum or locust bean gum, the viscosity is more than when either one is used alone, so less of each can be used.

The backbone of Xanthan gum is similar to cellulose, but the trisacharide side chains of mannose and glucuronic acid make the molecule rigid, and allow it to form a right-handed helix. These features make it interact with itself and with other long chain molecules to form thick mixtures and gels in water.

BIJAN - NEW IDEAS NEW REALITIES