Dextrin is any one of several substances produced by the partial chemical breakdown of starch. Dextrins are used mainly as adhesives and for the sizing, or stiffening, of paper and textiles. The gum on postage stamps is pure dextrin.
Chemically, dextrins are similar to starches. Dextrin molecules are composed of many identical groups of atoms, each group containing six carbon, ten hydrogen, and five oxygen atoms. Starch molecules contain an even greater number of the same groups of atoms.
Dextrins are produced by heating starch or by treating starch with acids or certain enzymes found in living things. When a starched garment is ironed, some of the starch is converted into dextrin by heating. Unlike starches, dextrins are soluble in cold water.