Biochemistry

Pectin in its pure form is a white powder without taste and odor, readily soluble in water. In plant tissues, 1/4 of the pectin substances are in the form of soluble pectin, which is part of the cell sap, and 3/4 are water-insoluble protopectin. Protopectin forms the intercellular layer in the plant tissue and determines the hardness of the latter. A characteristic property of many polysaccharides is their ability to gel in aqueous solutions. For this, it is necessary that the linear molecules are organized into a loose spatial grid, in the cells of which there is water. In pectin gels, the network nodes are formed due to the highly methylated regions of different chains of pectic acids, which are bound in aqueous solutions by hydrophobic interactions, and the low-methylated and therefore well hydrated regions form interstitial spaces. Therefore, the more methoxyl groups in the pectin molecule, the greater the gelling capacity of these compounds. High gelling ability is distinguished by pectin of a number of varieties of apples, oranges , quinces, black currants. Vegetable pectin is characterized by a low ability to form gels. Obtaining pectin gels in the presence of sucrose is the basis of confectionery , such as the manufacture of preserves, jams, marmalades, marshmallows, jellies, etc. The gelling ability of pectin in the presence of sugar increases in acidic solutions. So, for gelling 750 g of an acidic sugar solution, 1 g of pectin is enough . The ripening process of fruits, vegetables and berries, as well as their softening during thermal cooking, are associated with transformations of pectin substances. During the development of plant tissues, insoluble protopectin accumulates in them. During the ripening and storage of fruits and vegetables, the content of protopectin gradually decreases and soluble pectin accumulates at the same time. This process is catalyzed by the enzyme protopectinase. At the same time, the tissues of plant material become softer and more tender. The heat treatment of plant products weakens the adhesion between cells, as protopectin turns into pectin and the texture of the fabric softens. Pectin substances play a large role in nutrition: they promote normal digestion, as they stimulate intestinal motor activity, remove heavy metal salts from the body, bind excess cholesterol, and play the role of anti-radiation compounds. Heteropolysaccharides (mucopolysaccharides, hemicelluloses) consist of various types of monosaccharides (glucose, galactose) and their derivatives (amino sugars, hexuronic acids). Other substances were also found in their composition: nitrogenous bases, organic acids. 152