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Pectin is a heterosaccharide in the cell wall of plants. Pectins are very variable in composition; chain lengths are variable and there is a high complexity in the combination and order of each of the monosaccharide derivative units. It is synthesised in the plant Golgi apparatus and forms a matrix in which the hemicellulose polysacharides of the plant cell are embedded. An important part of fruit walls, pectin is broken down to pectinic acid and finally pectic acid. During this chemical breakdown process, the fruit gets softer as the cell walls degenerate.
Pectin is composed of three main polysaccharide types; polygalacturonan (composed of repeated galacturonic acid monosaccharide subunits), rhamnogalacturonan I (composed of alternating rhamnose and galacturonic acid subunits) and rhamnogalacturonan II (a complex, highly branched polysaccharide).
Apples, plums and oranges contain much pectin, and pectin is sometimes found in yogurt, while soft fruits like cherries and strawberries contain little pectin.
Pectin is commonly used as the active ingredient in cough drops because it coats the upper trachea and prevents the spasms which precede coughing. Under acidic conditions, pectin forms a gel. This effect is used for making jams and jellies.
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