Kids Research Express

Starch , common name applied to a white, granular or powdery, odorless, tasteless, complex carbohydrate, (C 6 H 10 O 5 ) x , abundant in the seeds of cereal plants and in bulbs and tubers. Molecules of starch are made of hundreds or thousands of atoms, corresponding to values of x, as given in the formula above, that range from about 50 to many thousands. Starch molecules are of two kinds. In the first kind, amylose, which constitutes about 20 percent of ordinary starch, the C 6 H 10 O 5 groups are arranged in a continuous but curled chain somewhat like a coil of rope; in the second kind, amylopectin, considerable side-branching of the molecule occurs. Starch is manufactured by green plants during the process of photosynthesis . It forms part of the cell walls in plants, constitutes part of rigid plant fibers, and serves as a kind of energy storage for plants, because its oxidation to carbon dioxide and water releases energy. The granules of starch present in any

Dextrin , amorphous, soluble carbohydrate, (C 6 H 10 O 5 ) n , produced by the action on starch paste of acids, heat, or enzymes such as diatase. The first product formed in this reaction is soluble starch, which in turn hydrolyzes to form dextrin. Dextrin is prepared commercially by moistening potato starch with weak nitric acid and then drying and heating the mass at 110° C (230° F). Dextrin is used in the manufacture of beer and as a substitute for gum arabic in printing cotton fabrics. It is also used commercially as an adhesive.

Hydrolysis , type of chemical reaction in which a molecule of water , formula HOH, reacts with a molecule of a substance AB, in which A and B represent either atoms or groups of atoms. In the reaction the water molecule breaks into the fragments H + and OH - ; and the molecule AB breaks into A + and B - ; the fragments then join to give the final products AOH and HB. This kind of reaction is called a double decomposition or an exchange.