Pectin

Chemical composition

Pectins are acid polysaccharide polymers. Pectins are made up of a principal chain of Uronic acid dependant into 1-4. Regularly between these monomers molecules of Rhamnose S by connections 1-2 and 1-4 are intercalated. This type of connection between the molecules of uronic acid and rhamnose forms elbows. The pectin macromolecule resembles a zigzag. This fitting gives properties particular to pectins. To supplement the chemical composition of pectins it should be specified that there exist ramifications on the level of the uronic acids as on the level of rhamnose by molecules (ex galactane, arabinane etc). This great heterogeneity makes that one must rather speak about pectins that pectin. Moreover this diversity makes pectins of the complex molecules.

Chemical properties

The molecules of uronic acid have functions carboxyls. This function confers on pectins the capacity to exchange ions. In the case of the vegetable walls these ions are especially the Calcium coming from the apoplasmic circulation. These bivalent ions have the capacity to form calcic bridges between two groupings carboxyls of two different pectin molecules. The cell controls the proportion of function carboxyl. Indeed it can esterify in a reversible way its functions by méthylant them by a pectin-méthylestérase. According to the proportion of methylated monomers or not, the chain is more or less acid. This acidity is also controlled by pumps with proton controlled in particular by the Auxine. The strong concentration in protons causes the replacement of calcium then. In conclusion a strong proportion of function carboxyl in an alkaline pH supports the cohesion of the pectin molecule enters. Chains can thus bind and pectins form a gel then. Just as an increase in the methylation coupled to strong aciditée the relaxation of pectin supports. In experiments, the researchers can stop this gelation by removing calcium artificially. This is carried out during the extraction by the EDTA, which is a powerful Chélateur calcium. This can also be carried out also if the pH is lowered.

Physiological roles

Pectins are one of the components of the vegetable Paroi. They are also the prevalent compound within the average Lamelle. They maintain together the cells of the vegetable fabrics. Pectins play a structural part depend on the ionic conditions of the medium (H+/Ca++ report/ratio). The formed chains are connected between them to constitute a network or freezing. This unit makes it possible to store great quantity of Eau. The hydrolysis of pectins is remarkable during the maturation of the fruits when the cellulose fibers become looser.

Industrial applications

The hydrolysis of pectins is necessary to allow the spontaneous clarification of fruit juices or the Moût S before alcoholic fermentation as in the case of the development of the rosy Wine. It is then carried out by enzymage.

Genetic modification

American researchers modified the Génome Tomate. This modification carries on coding genes the training of pectins. This results in a less percentage of pectins in the transgenic tomatos . This pectin deficiency makes it possible to obtain firmer tomatos longer. These tomatos are the first edible plants transgenic put on the US market.

Medical interest

Pectin seems to have properties entérosorbante S, i.e. which it can adsorb certain heavy metals and radionuclides at the time of its passage in the digestive tract. This property could be related to its capacity to exchange Ion S. Pectin is according to scientists of Bélarus able to help the organization not to absorb some Radionucléide S, of which the radioactive Cesium 137 , and this, without the side effects of the chemical Chélateur S, but with other effects. It as seems to be able to help the organization with better or more quickly débarasser of Cesium as it contains; Its effectiveness is discussed, but pectin for example is used in food complement in the children living in the zones exposed to the repercussions of Tchernobyl, which are victims of pathologies related to the accumulation of cesium introduced with drink or food. Nesterenkocite an experiment having related to 64 children of the district Bélarus of Gomel, very contaminated by the repercussions of Tchernobyl. These children spent one month in a Sanatorium where they consumed only not contaminated food. A group-witness took pectin morning and evening; the other, a Placebo. After one month, the children of the pectin group saw their rate cesium-137 to decrease by 62,6%. In the other group, the cesium dropped only by 13,9%.
L' ACRO also in France found that children having received pectin at the time of their stay in France saw (on average) their contamination with Cesium 137 dropping by 31% compared with only 15% at cheux which did not receive any (out the share naturally present in the food). Always according to the ACRO, pectin and the export of cesium accelerates increases, but less quickly than those say it which promoted it.
Des ONG helps the families to be provided in “ Vitapect ”, so that their children can make regular cures of them (3 per annum ideally, according to the promoters of pectin), while being aware that a better solution would be to rehouse the families in not contaminated zones.

Culinary interest

A recent study did not find an interaction molecular specific between flavors and pectin, but confirms that pectin, even with low dose (0,1%) does not modify the aromatic compounds; it blocks them or slows down simply, including most volatile and/or Hydrophobe S, in jams or cold. These aromatic molecules are encagées in the grid tridimentionnel pectin molecules, but they to some extent slackened and are recognized by the taste buds and the sense of smell when the frost is eaten.

The pectin is usually present in the vegetable kingdom. The pectin the commercial, of which that often used to thicken the Jam S and the Gelée S is extracted from the marc of desiccated Pomme S. It is sold in liquid form or of crystals. One finds also Sucre pre-added with pectin.

The success of jams and the frosts depends on the proportion of sugar, pectin and acids contained in the fruits used.

Degradation

Pectin is a relatively stable molecule, resistant to temperatures of more than 100 °C, but it is in the nature degraded by Enzyme S (“ pectin lyase ”) produced by microbes or mushrooms, of which some ( Saccharomyces cerevisiae , Bacillus subtilis , yeasts…) were studied for possible industrial uses. Many species phytopathogenes (ex: Erwinia will carotovora , bacterium cold resistant phytopathogene) probably secrete such enzymes, necessary to attack the vegetable cells. The use of these enzymes is at the base of the clarification of fruit juices such as for example at the time of the operation of Débourbage in the wine making of the white wines and the rosy wines

See too

Internal bonds

External bonds

Card Inist
Card Inist Extraction of pectin/depolymerization/output)

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