PECTIN SUBSTANCES

Pectin substances, plant mucilages contained in juices, fruits (apples contain 1% P. s., lemons 1.95%), and fleshy rhizomes (in beets over 25%). Discovered in 1825 by Braconnot. They have found application in the food industry (in the preparation of fruit jellies, purees, marmalades, preserves, etc.) due to their ability to gelatinize when boiled with sugar in the presence of organic acids. Amorphous. Poorly soluble in cold water, in boiling water they pass into soluble hydropectin; from aqueous solutions they are precipitated by alcohol in the form of a jelly. Very difficult to separate from impurities, for which reason the chemical individuality of various P. s. cannot yet be considered firmly established. P. s. are derivatives of carbohydrates, containing residues of D-galactose, arabinose, and D-galacturonic acid (stereoisomer of glucuronic acid). According to Ehrlich (F. Ehrlich), P. s. are Ca- and Mg-co-salts of anhydroarabinosido-galactosido-methoxy-tetragalacturonic acid. During hydrolysis, arabinose is easily cleaved off and pectinic acid-galactosido-talacturonic acid is formed, containing methoxyl groups and constructed analogously to paired glucuronic acids of animals. In P. s., insoluble pectose (protopectin), soluble pectin, and pectinic acid are distinguished. During enzymatic or acidic hydrolysis, pectose passes into pectin and then into pectinic acid. Pectose is found mainly in fleshy rhizomes and unripe fruits, pectin in ripe fruits, pectinic acid is formed during the decay of plants. Feeding experiments with P. s. on animals gave good results. The D-galactose formed during the hydrolysis of P. s. is easily assimilated by the body. The raw material for obtaining P. s. consists of apple pomace (obtained in cider production), pressed lemons (remaining in the production of citric acid), and delignified beet shavings from sugar factories. The raw material to remove impurities is extracted with cold water, then P. s. are extracted with boiling water and the extract is evaporated in a vacuum. P. s. are a binding substance for the fibers of flax, hemp, etc.; to destroy P. s., use is made of enzymatic action (retting of flax) OR PURE CHEMICAL ACTION.