starch

Widely distributed, high-molecular-mass carbohydrate, produced by plants as a food store; main dietary sources are cereals, legumes, and tubers, including potatoes. It consists of varying proportions of two glucose polymers (polysaccharides): straight-chain (amylose) and branched (amylopectin) molecules.

Purified starch is a white powder used to stiffen textiles and paper and as a raw material for making various chemicals. It is used in the food industry as a thickening agent. Chemical treatment of starch gives rise to a range of ‘modified starches’ with varying properties. Hydrolysis (splitting) of starch by acid or enzymes generates a variety of ‘glucose syrups’ or ‘liquid glucose’ for use in the food industry. Complete hydrolysis of starch with acid generates the monosaccharide glucose only. Incomplete hydrolysis or enzymic hydrolysis yields a mixture of glucose, maltose, and nonhydrolysed fractions called dextrins.

The chemical test for starch consists of adding a drop of iodine solution to the substance. It will turn bright blue if starch is present.

A link was identified in 1994 between a diet low in starch and cancer of the colon.