Pectin
[2][3][dubious – discuss] Commercially produced pectin is a white-to-light-brown powder, produced from citrus fruits for use as an edible gelling agent, especially in jams and jellies, dessert fillings, medications, and sweets; as a food stabiliser in fruit juices and milk drinks,[4] and as a source of dietary fiber.
Pectin is deposited by exocytosis into the cell wall via vesicles produced in the Golgi apparatus.
[8] A similar process of cell separation caused by the breakdown of pectin occurs in the abscission zone of the petioles of deciduous plants at leaf fall.
[13] The mechanism appears to be an increase of viscosity in the intestinal tract, leading to a reduced absorption of cholesterol from bile or food.
[14] In the large intestine and colon, microorganisms degrade pectin and liberate short-chain fatty acids that have a positive prebiotic effect.
[16][17][18] Another structural type of pectin is rhamnogalacturonan II (RG-II), which is a less frequent, complex, highly branched polysaccharide.
[23] The ratio of esterified to non-esterified galacturonic acid determines the behaviour of pectin in food applications – HM-pectins can form a gel under acidic conditions in the presence of high sugar concentrations, while LM-pectins form gels by interaction with divalent cations, particularly Ca2+, according to the idealized 'egg box' model, in which ionic bridges are formed between calcium ions and the ionised carboxyl groups of the galacturonic acid.
[citation needed] Some plants, such as sugar beet, potatoes and pears, contain pectins with acetylated galacturonic acid in addition to methyl esters.
[26] Thiolated pectin exhibits substantially improved gelling properties since this thiomer is able to crosslink via disulfide bond formation.
Also, gels from amidated pectin are thermoreversible; they can be heated and after cooling solidify again, whereas conventional pectin-gels will afterwards remain liquid.
[citation needed] Pears, apples, guavas, quince, plums, gooseberries, and oranges and other citrus fruits contain large amounts of pectin, while soft fruits, like cherries, grapes, and strawberries, contain small amounts of pectin.
[citation needed] From these materials, pectin is extracted by adding hot dilute acid at pH values from 1.5 to 3.5.
After filtering, the extract is concentrated in a vacuum and the pectin is then precipitated by adding ethanol or isopropanol.
After drying and milling, pectin is usually standardised[clarification needed] with sugar, and sometimes calcium salts or organic acids, to optimise performance in a particular application.
[32] In some countries, pectin is also available as a solution or an extract, or as a blended powder, for home jam making.
[citation needed] The classical application is giving the jelly-like consistency to jams or marmalades, which would otherwise be sweet juices.
[citation needed] For various food applications, different kinds of pectins can be distinguished by their properties, such as acidity, degree of esterification, relative number of methoxyl groups in the molecules, etc.
Pectin is also used in wound healing preparations and speciality medical adhesives, such as colostomy devices.
It was found that pectin from different sources provides different gelling abilities, due to variations in molecular size and chemical composition.
[citation needed] In ruminant nutrition, depending on the extent of lignification of the cell wall, pectin is up to 90% digestible by bacterial enzymes.
[citation needed] Yablokov et al., writing in Chernobyl: Consequences of the Catastrophe for People and the Environment, quote research conducted by the Ukrainian Center of Radiation Medicine and the Belarusian Institute of Radiation Medicine and Endocrinology, concluded, regarding pectin's radioprotective effects, that "adding pectin preparations to the food of inhabitants of the Chernobyl-contaminated regions promotes an effective excretion of incorporated radionuclides" such as cesium-137.
[44] During the Second World War, Allied pilots were provided with maps printed on silk, for navigation in escape and evasion efforts.
[45] At the Joint FAO/WHO Expert Committee Report on Food Additives and in the European Union, no numerical acceptable daily intake (ADI) has been set, as pectin is considered safe.
