dextrin

 

any one of a number of carbohydrates having the same general formula as starch but a smaller and less complex molecule. They are polysaccharides and are produced as intermediate products in the hydrolysis of starch by heat, by acids, and by enzymes. Their nature and their chemical behavior depend to a great extent on the kind of starch from which they are derived. For example, some react with iodine to give a reddish-brown color, others a blue, and still others yield no color at all. For commerical use dextrin is prepared by heating dry starch or starch treated with acids to produce a colorless or yellowish, tasteless, odorless powder which, when mixed with water, forms a strongly adhesive paste. It is used widely in adhesives, e.g., for postage stamps, envelopes, and wallpapers, and for sizing paper and textiles.

Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch. Dextrins are mixtures of linear α-(1,4)-linked D-glucose polymers. They have the same general formula as carbohydrates but are of shorter chain length. Industrial production is generally performed by acidic hydrolysis of potato starch. Dextrins are water soluble, white to slightly yellow solids which are optically active. Analytically, dextrins can be detected with iodine solution, giving a red coloration.

The cyclical dextrins are known as cyclodextrins. They are formed by enzymatic degradation of starch by certain bacteria, for example Bacillus macerans. Cyclodextrins have toroidal structures formed by 6-8 glucose residues.

Dextrins find widespread use in industry, due to their non-toxicity and their low price. They are used as water soluble glues, as thickening agents in food processing, and as binding agent in pharmaceuticals. In pyrotechnics they are added to colored fire formulas, allowing them to solidify as pellets or "stars." Cyclodextrins find additional use in analytical chemistry as a matrix for the separation of hydrophobic substances, and as excipients in pharmaceutical formulations. Not all forms of dextrin are digestible, and indigestible dextrin is sometimes used in fiber supplements.

For example, maltodextrin is a moderately sweet polysaccharide used as a food additive. It is produced from starch and is usually found as a creamy white hygroscopic powder. Maltodextrin is easily digestible, being absorbed as rapidly as glucose. The CAS registry number of maltodextrin is 9050-36-6.

Maltodextrin can be derived from any starch. In the US this starch is usually corn or potato, elsewhere such as in Europe it is commonly wheat. This is important for coeliacs since the wheat-derived maltodextrin can contain traces of gluten.

Foods containing maltodextrin may contain traces of amino acids, including glutamic acid as a manufacturing by-product. The amino acids traces would be too small to have any dietary significance.

See also

• Modified starch
• Starch gelatinization
• Dextran

External links

• EAFUS
• Maltodextrin entry on Grokfood.com

Donate to Wikimedia