The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Pectic Substances

high-molecular polysaccharides that are formed in all land plants and many species of algae. Especially large quantities of pectic substances are found in fruits, berries, flax stems, and root crops—in particular, the sugar beet. Water-soluble pectic substances are called soluble pectins, and water-insoluble pectic substances protopectins.

Pectic substances are unbranched polygalacturonides, that is, polymers of galacturonic acid in which some of the carboxyl groups are esterified with methanol. Neutral monosaccharides, such as galactose, rhamnose, arabinose, and xylose, are also present in pectic substances. The primary cell walls and the intercellular substance of plants consist mostly of protopectins; soluble pectin are found in the cell sap. Pectic substances contribute to a plant tissue’s turgor, increase a plant’s resistance to drought, and help preserve fruits and vegetables under storage conditions.

As a fruit ripens, pectolytic enzymes alter the quantity and nature of pectic substances, and this produces the characteristic softening. Higher plants, fungi, and bacteria contain the pectolytic enzymes polygalacturonase, pectinesterase, and transeliminase. Many fungi and bacteria synthesize pectolytic enzymes and thus are able to decompose pectic substances. These enzymes also determine the pathogenicity of certain micro-organisms.

Pectic substances that are extracted from plants commercially or in the laboratory are called pectins. An industrially important property of pectins is the ability of their solutions to form firm gels or, in the presence of sugar and acids, to form jellies. Thus, they are used as natural gelling agents in the food industry, for example, for preparing preserves and confectioneries. Pectins are extracted from apple pomace, the rind of citrus fruits, citrons, sugar beet pulp, and the capitula of sunflowers. Preparations that contain pectolytic enzymes are obtained from molds or from plant tissue and are used to clarify wines and juices. Pectolytic enzymes are used to process fiber plants, such as flax and hemp. Pectic substances are used in the treatment of gastric diseases and as preventive agents in certain harmful industrial conditions.

REFERENCES

Khimiia uglevodov. Moscow, 1967.
Sapozhnikova, E. V. Pektinovye veshchestva i pektoliticheskie fermenty. Moscow, 1971.
Kertesz, Z. I. Pectic Substances. New York, 1951.
Worth, H. G. “The Chemistry and Biochemistry of Pectic Substances.” Chemical Reviews, 1967, vol. 67, no. 4.
Fogarty, W. M., and O. P. Ward. “Pectic Substances and Pectinolytic Enzymes.” Process Biochemistry, 1972, vol. 7, no. 8.

E. V. SAPOZHNIKOVA

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References in periodicals archive

Pomegranate contains from 8 to 19 percent of glucose and fructose, from 3 to 7 percent - citric acid, a large number of minerals, vitamins, fiber, and pectic substances. This fruit is very rich in antioxidants.

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Generally, pectic substances are physiologically active structural polysaccharides of the plant cell wall, which play an important role in the middle lamella.

Isolation and Characterization of Pectic Polysaccharide Fraction from In Vitro Suspension Culture of Fumaria officinalis L

Plant cell wall can be categorized into 3 layers: layer one is adhesive between cell and another called "middle lamella" composed of calcium pectate (pectic acid binding [Ca.sup.2+]), layer two is a real cell wall synthesized during cell division called "primary cell wall" composed of cellulose, hemicellulose, and pectic substances, and layer three synthesized after primary cell wall or in nongrowing stage of cell called "secondary cell wall" composed of cellulose, hemicellulose, and lignin [27, 28].

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For quantification of total pectic substances, the methodology described by MAGALHAES (1991) was adopted, with modifications.

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Pectolytic enzymes (pectinases) are the ones which catalyze decomposition of pectic substances [1].

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Pectinases catalyze hydrolysis of pectic substances readily soluble in water.

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Pectic substances are complex polysaccharides with high molecular weight [46], they form the major components of the middle lamella and primary plant cell wall of higher plants [15], these substances account for 0.5%-4.0% of the fresh weight of plant material [17].

Isolation, production and characterization of extracellular pectin lyase from Bacillus subtilis