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Fruit pectin

Pectin is a heteropolysaccharide which is found in the form of a water insoluble parent pectic substance (protopectin) in the primary cell wall and the middle lamella of green land plants. Pectin is the generic designation for compounds which result from restricted hydrolysis of protopectin. Pectin, along with cellulose, hemicellulose and lignin, constitute the major components of plant tissue. The cellulose, hemicellulose and lignin portions are located within the cell structure where they provide support to the cell. The pectic portion is located between cells where it acts as a biological adhesive to hold the cells together. Pectin is a linear polymer composed of D-galactopyranosyl uronic acid units which are linked through alpha-1 4-glycosidic bonds forming long chains of polygalacturonic acid. Part of the carboxyl groups of the uronic acid units are esterified with methanol. In the plants the residual carboxyl groups are partly or completely neutralised with cations of calcium and magnesium which inherently are contained in the plant tissues. Pectin is divided into two main categories: high methoxylated pectin (HM pectin), which are characterized by a degree of methoxylation above 50% and low methoxylated pectin (LM pectin) having a degree of methoxylation below 50%. Pectins are carbohydrates generally obtained from dilute acid extracts of citrus or apple pulp. They, are also present in the cellular walls of vegetables and fruits. Pectins are also found in root crops such as carrots and beetroot, as well as in tubers, such as potatoes. Pectin has long been used in the home for gelling jams employing, for example, apple core or quinces as the pectin source. Today, the fruit and confectionery industry uses pectin for its gelling properties in acid and sugar media. It is also used in cosmetics, drugs, protective colloids, emulsifying agents, and dehydrating agents.

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