PECTINS

Pectins are a pentose, a polyol and a hydroxyaldehyde.
Pectins are a polysaccharide is rich in galacturonic acid and possesses a complex structure and function.
Pectins occurs as a coarse or fine, yellowish-white, odorless powder that has a mucilaginous taste.

CAS:    9000-69-5
MF:    C6H12O6
EINECS:    232-553-0

Synonyms
APPLE PECTIN FOOD GRADE - SPECIAL;APPLE PECTIN, FOOD GRADE;APPLE PECTIN, USP;PECTIN, CITRUS USP SLOW SET;Polyhalactyronic acid;POLY-D-GALACTURONIC ACID METHYL ESTER;POLYGALACTURONIC ACID METHYL ESTER;PARTIALLY METHOXYLATED POLYGALACTURONIC ACID

Pectins are a heteropolysaccharide, a structural polymer contained in the cell walls and middle lamellae of terrestrial plants. 
The principal chemical component of Pectins are galacturonic acid (a sugar acid derived from galactose) which was isolated and described by Henri Braconnot in 1825.
Commercially produced Pectins are 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; and as a source of dietary fiber.

Biology
Natural occurrence
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.
Typical levels of pectins in fresh fruits and vegetables are:

Apples, 1–1.5%
Apricots, 1%
Cherries, 0.4%
Oranges, 0.5–3.5%
Carrots 1.4%
Citrus peels, 30%
Rose hips, 15%[

Pectins are composed of complex polysaccharides that are present in the primary cell walls of a plant, and are abundant in the green parts of terrestrial plants.
Pectins are the principal component of the middle lamella, where it binds cells. 
Pectins are deposited by exocytosis into the cell wall via vesicles produced in the Golgi apparatus.
The amount, structure and chemical composition of Pectins are different among plants, within a plant over time, and in various parts of a plant. 
Pectins are an important cell wall polysaccharide that allows primary cell wall extension and plant growth.
During fruit ripening, Pectins are broken down by the enzymes pectinase and pectinesterase, in which process the fruit becomes softer as the middle lamellae break down and cells become separated from each other.
A similar process of cell separation caused by the breakdown of pectins occurs in the abscission zone of the petioles of deciduous plants at leaf fall.

Human nutrition
Pectins are a natural part of the human diet and although not digested in the small intestine, it is fermented in the large intestine. 
Pectins has a positive effect on decreasing overall LD L cholesterol levels as well as lowering post-prandial glucose levels.
The daily intake of pectins from fruits and vegetables can be estimated to be around 5 g if approximately 500 g of fruits and vegetables are consumed per day.
In human digestion, pectin binds to cholesterol in the gastrointestinal tract and slows glucose absorption by trapping carbohydrates. 
Pectins are thus a soluble dietary fiber. 
In non-obese diabetic (NOD) mice pectin has been shown to increase the incidence of autoimmune type 1 diabetes.

A study found that, after consumption of fruit, the concentration of methanol in the human body increased by as much as an order of magnitude due to the degradation of natural pectin (which is esterified with methanol) in the colon.
Consumption of pectin has been shown to slightly (3–7%) reduce blood LDL cholesterol levels. The effect depends upon the source of pectin; apple and citrus pectins were more effective than orange pulp fibre pectin.
The mechanism appears to be an increase of viscosity in the intestinal tract, leading to a reduced absorption of cholesterol from bile or food.
In the large intestine and colon, microorganisms degrade pectins and liberate short-chain fatty acids that have a positive prebiotic effect.

Chemistry
Definition and structure
Pectins are a heteropolysaccharide with a high proportion of D-galacturonic acid (≈ 65%) in its repeat units.
As the polymer's main chain contains α-L-rhamnose in addition to galacturonic acid, the systematic name for pectin is rhamno-galacturonic acid. 
The incorporation of rhamnose units disrupts the otherwise linear poly(galacturonic acid) chain, introducing bends (or "kinks"). 
Many rhamnose units in pectins carry oligomeric side chains of neutral sugars such as arabinose, galactose, or xylose. 
These branched sections are referred to as "hairy" regions, while the unbranched stretches composed mainly of galacturonic acid are termed "smooth" regions. 
In further detail, the hairy and smooth regions can be divided into distinct structural domains (that exist within the same pectin molecule): Smooth regions comprise homogalacturonan (HG), xylogalacturonan (XGA), and apiogalacturonan (APGA), while the hairy regions are made up of rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II).

The carboxyl groups of polygalacturonic acid are frequently esterified with methanol or acetic acid. 
The degree of esterification and acetylation varies depending on the source of the pectin and has a decisive impact on its chemical properties. 
Pectins are therefore classified according to their degree of methylation (DM) and degree of acetylation (DA), which represent the ratio of esterified galacturonic acids (methylated or acetylated) to total galacturonic acids. 
Functionally, three types of pectins are distinguished:

Pectic acids: degree of methylation less than 5% (DM<5)
Weakly methylated (LM) pectins: degree of methylation less than 50% (DM<50)
Highly methylated (HM) pectins: degree of methylation greater than 50% (DM>50)
Amidated pectin shows enhanced tolerance to varying calcium concentrations. 
Thiolated pectin, capable of forming disulfide crosslinks, exhibits superior gelling properties beneficial for pharmaceutical and food applications.

Pectins Chemical Properties
Melting point: 174-180 °C (decomp)
storage temp.: room temp
solubility: H2O: soluble0.02g/10 mL, clear to hazy, colorless to very faintly yellow
form: Powder
color: Yellow to Pale Brown
Odor: wh. to yel. powd. or syrupy conc., pract. odorless
biological source: plant fruit (Apple)
Water Solubility: It is soluble in water.
Merck: 14,7063
Cosmetics Ingredients Functions: BINDING
VISCOSITY CONTROLLING
EMULSION STABILISING
Cosmetic Ingredient Review (CIR): Pectin (9000-69-5)
EPA Substance Registry System: Pectins (9000-69-5)

Uses    
In the preparation of jellies and similar food products: Owens et al., "Factors Influencing Gelation with Pectin" in Natural Plant Hydrocolloids, Advances in Chemistry Series (ACS, Washington, 1954) pp 10-15.
Pectins are used as a thickening agent in cosmetic preparations given its gelling properties. 
Pectins are is soothing and mildly acidic and extracted from apples or the inner portion of citrus fruit rind.
Pectin is a gum that is the methylated ester of polygacturonic acid. it is obtained from citrus peels and apple pomace. 
the degree of meth- ylation (dm) or esterification (de) refers to the percentage of acid groups which are present as the methyl ester. 
Pectins are divided into two main groups: high methoxy (hm) pectin, having 50% or greater esterification, and low methoxy (lm) pectin, having less than 50% esterification. 
these pectins gel under different conditions. the lm pectins are subdivided into low methoxy amidated pectin and low methoxy conventional pectin. 
Pectins are broad group of pectic substances that contain more than a negligible proportion of methyl ester groups and all the unes- terified carboxyl groups are free. 
the divalent salts of pectinic acid are only slightly soluble in water and must be converted to the sodium or potassium form for dissolution.

The main use for pectin is as a gelling agent, thickening agent and stabiliser in food.
In some countries, Pectins are also available as a solution or an extract, or as a blended powder, for home jam making.
The classical application is giving the jelly-like consistency to jams or marmalades, which would otherwise be sweet juices.
Pectins also reduces syneresis in jams and marmalades and increases the gel strength of low-calorie jams. 
For household use, pectin is an ingredient in gelling sugar (also known as "jam sugar") where it is diluted to the right concentration with sugar and some citric acid to adjust pH.
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. 
For instance, the term "high methoxyl" refers to pectins that have a large proportion of the carboxyl groups in the pectin molecule that are esterified with methanol, compared to low methoxyl pectins:

high methoxyl pectins are defined as those with a degree of esterification equal to or above 50, are typically used in traditional jam and jelly making; such pectins require high sugar concentrations and acidic conditions to form gels, and provide a smooth texture and suitable to be used in bakery fillings and confectionery applications;
low methoxyl pectins have a degree of esterification of less than 50, can be either amidated or non-amidated: the percentage level of substitution of the amide group, defined as the degree of amidation, defines the efficacy of a pectin; low methoxyl pectins can provide a range of textures and rheological properties, depending on the calcium concentration and the calcium reactivity of the pectin chosen—amidated low methoxyl pectins are generally thermoreversible, meaning they can form gels that can melt and reform, whereas non-amidated low methoxyl pectins can form thermostable gels that withstand high temperatures; these properties make low methoxyl pectins suitable for low sugar and sugar-free applications, dairy products, and stabilizing acidic protein drinks.
For conventional jams and marmalades that contain above 60% sugar and soluble fruit solids, high-ester (high methoxyl) pectins are used. With low-ester (low methoxyl) pectins and amidated pectins, less sugar is needed, so that diet products can be made. 
Water extract of aiyu seeds is traditionally used in Taiwan to make aiyu jelly, where the extract gels without heating due to low-ester pectins from the seeds and the bivalent cations from the water.

Pectins are used in confectionery jellies to give a good gel structure, a clean bite and to confer a good flavour release. 
Pectins can also be used to stabilise acidic protein drinks, such as drinking yogurt, to improve the mouth-feel and the pulp stability in juice based drinks and as a fat substitute in baked goods.
Typical levels of pectin used as a food additive are between 0.5 and 1.0% – this is about the same amount of pectin as in fresh fruit.
In medicine, pectin increases viscosity and volume of stool so that it is used against constipation and diarrhea.
Pectins were one of the main ingredients used in Kaopectate – a medication to combat diarrhea – along with kaolinite. 
Pectins has been used in gentle heavy metal removal from biological systems.
Pectins are also used in throat lozenges as a demulcent.

In cosmetic products, pectin acts as a stabiliser. 
Pectins are also used in wound healing preparations and speciality medical adhesives, such as colostomy devices.
Sriamornsak revealed that pectin could be used in various oral drug delivery platforms, e.g., controlled release systems, gastro-retentive systems, colon-specific delivery systems and mucoadhesive delivery systems, according to its intoxicity and low cost. 
Pectins was found that pectin from different sources provides different gelling abilities, due to variations in molecular size and chemical composition. 
Like other natural polymers, a major problem with Pectins are inconsistency in reproducibility between samples, which may result in poor reproducibility in drug delivery characteristics.

In ruminant nutrition, depending on the extent of lignification of the cell wall, Pectins are up to 90% digestible by bacterial enzymes. 
Ruminant nutritionists recommend that the digestibility and energy concentration in forages be improved by increasing pectin concentration in the forage.
In cigars, Pectins are considered an excellent substitute for vegetable glue and many cigar smokers and collectors use pectin for repairing damaged tobacco leaves on their cigars.

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. 
The authors reported on the positive results of using pectin food additive preparations in a number of clinical studies conducted on children in severely polluted areas, with up to 50% improvement over control groups.
During the Second World War, Allied pilots were provided with maps printed on silk, for navigation in escape and evasion efforts. 
The printing process at first proved nearly impossible because the several layers of ink immediately ran, blurring outlines and rendering place names illegible until the inventor of the maps, Clayton Hutton, mixed a little pectin with the ink and at once the pectin coagulated the ink and prevented Pectins are from running, allowing small topographic features to be clearly visible.

Agricultural Uses    
Pectins are high molecular weight polyuronide. 
Pectins are related to the carbohydrate family and is present in fruits and berries.
Pectin occurs in varying amounts in fruits and plants. 
Pectins are contains carbon, hydrogen and oxygen, and on hydrolysis, yields glycosides and galachronic acid. 
Pectins can form a gel when it absorbs water.
Commercially, the primary source of the commonly used pectin is lemon and lime peel; other citrus fruits lie orange and grapefruit may also be used. 
Pectins are widely used in the food industry, principally in gel preparation.
Pectins are also used in making drugs, protective colloids, emulsifying agents, etc.

Pharmaceutical Applications    
Present in multi-ingredient preparations for the management of diarrhea, constipation, and obesity; Pectins has also been used as an emulsion stabilizer.
Experimentally, pectin has been used in gel formulations for the oral sustained delivery of ambroxol.
Pectin gel beads have been shown to be an effective medium for controlling the release of a drug within the gastrointestinal (GI) tract.
Pectins has also been used in a colon-biodegradable pectin matrix with a pH-sensitive polymeric coating, which retards the onset of drug release, overcoming the problems of pectin solubility in the upper GI tract.
Amidated pectin matrix patches have been investigated for the transdermal delivery of chloroquine,and gelling pectin formulations for the oral sustained delivery of paracetamol have been investigated in situ.
Pectin-based matrices with varying degrees of esterification have been evaluated as oral controlled-release tablets. 
Lowmethoxy pectins were shown to have a release rate more sensitive to the calcium content of the formulation.
Pectins have been used as a component in the preparation of mixed polymer microsphere systems with the intention of producing controlled drug release.

Biochem/physiol Actions    
Pectins, a heterosaccharide component of terrestrial plant cell walls, is used as a substrate to identify, differentiate and characterized pectinase(s). 
Pectins are used to study its degradation by pectinolytic bacteria.

Purification Methods    
Dissolve the pectin in hot water to give a 1% solution, then cool, and make Pectins are to about 0.05M in HCl by addition of conc HCl, and precipitate it by pouring it slowly, with vigorous stirring into two volumes of 95% EtOH. 
After standing for several hours, the Pectins are filtered through a nylon cloth, then redispersed in 95% EtOH and stood overnight. 
The precipitate is filtered off, washed with EtOH/Et2O, then Et2O and dried in air.