Центральный Дом Знаний - Альгиновая кислота

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Альгиновая кислота

Альгиновая кислота (E400), полисахарид, вязкое резиноподобное вещество, извлекаемое из бурых водорослей (латPhaeophyceae, ламинария японская (латLaminaria japonica Aresch)). Содержание А.к. в ламинарии колеблется от 15 до 30 %.

А.к. нерастворима в воде и в большинстве органических растворителей. 1 часть А.к. адсорбирует 300 массовых частей воды, что обуславливает её применение как загустителя.

А.к. гетерополимер, образованный двумя мономерами — остатками полиуроновых кислот (D-маннуроновой и L-гулуроновой) в разных пропорциях, варьирующихся в зависимости от конкретного вида водорослей. Альгинаты в организме человека не перевариваются и выводятся через кишечник.

А.к. и альгинаты широко применяются в медицине (в качестве антацида) и как пищевые добавки (загустители). А.к. выводит из организма тяжёлые металлы (свинец, ртуть и др.) и радионуклиды. Многие целебные свойства морской капусты объясняются именно А.к.

Соли А.к.  — Альгинаты, в частности альгинат натрия (E401), альгинат калия (Е402) и альгинат кальция (Е404) используются в качестве пищевых добавок.

Альгинаты калия и натрия в воде образуют коллоидные растворы, в отличие от нерастворимой А.к.

В стоматологии альгинат с добавками используется в качестве слепочной массы — для изготовления оттиска челюсти, с дальнейшей отливкой гипсовой модели. Для аналогичных целей применяют и силиконовые слепочные массы.

Alginic acid, also called algin or alginate, is an anionic polysaccharide distributed widely in the cell walls of brown algae, where it, through binding water, forms a viscous gum. In extracted form it absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water. Its colour ranges from white to yellowish-brown. It is sold in filamentous, granular or powdered forms. 

It is a linear copolymer with homopolymeric blocks of (1-4)-linked β-D-mannuronate (M) and its C-5 epimer α-L-guluronate (G) residues, respectively,covalently linked together in different sequences or blocks.

The monomers can appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks). 

Commercial varieties of alginate are extracted from seaweed, including the giant kelp Macrocystis pyrifera, Ascophyllum nodosum, and various types ofLaminaria. It is also produced by two bacterial genera Pseudomonas and Azotobacter, which played a major role in the unravelling of its biosynthesispathway. Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications.  

Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles. It is also used for waterproofing and fireproofing fabrics, as a gelling agent, and for thickening drinks, ice cream and cosmetics.

Alginate is used in various pharmaceutical preparations such as Gaviscon, Bisodol, and Asilone. Alginate is used extensively as an impression-making material in dentistry, prosthetics, lifecasting and occasionally for creating positives for small-scale casting. It is also used in the food industry, for thickening soups and jellies.

Calcium alginate is used in different types of medical products, including burn dressings that promote healing and can be removed with less pain than conventional dressings.

Also, due to alginate's biocompatibility and simple gelation with divalent cations such as Ca2+, it is widely used for cell immobilization and encapsulation.

Alginic acid (alginato) is also used in culinary arts, most notably in the "Esferificación" (Sphereification) techniques of Ferran Adrià of El Bulli in Roses, Girona, where natural juices of fruits and vegetables are encapsulated in bubbles that "explode" on the tongue when consumed. One of the most famous examples of this use of alginic acid was when Ferran Adrià used alginic acid to make apple caviar. 

Due to its ability to absorb water quickly, alginate can be changed through a lyophilization process to a new structure that has the ability to expand. It is used in the weight loss industry as an appetite suppressant.

In March, 2010 researchers at Newcastle University announced that dietary alginates can reduce human fat uptake by more than 75%.

The chemical compound sodium alginate is the sodium salt of alginic acid. Its empirical formula is NaC6H7O6. Sodium alginate is a gum, extracted from the cell walls of brown algae 

Its form as a flavorless gum, is used by the foods industry to increase viscosity and as an emulsifier. It is also used in indigestion tablets and the preparation of dental impressions.

A major application for sodium alginate is in reactive dye printing, as thickener for reactive dyestuffs (such as the Procion cotton-reactive dyes) in textile screen-printing and carpet jet-printing. Alginates do not react with these dyes and wash out easily, unlike starch-based thickeners.

Sodium alginate is a good chelator for pulling radioactive toxins from the body, such as iodine-131 and strontium-90 that have taken the place of their non-radioactive counterparts.  It is also used inimmobilizing enzymes by inclusion.

As a food additive, sodium alginate is used especially in the production of gel-like foods. For example, bakers' "Chellies" are often gelled alginate "jam." Also, the pimento stuffing in prepared cocktail olives is usually injected as a slurry at the same time that the stone is ejected; the slurry is subsequently set by immersing the olive in a solution of a calcium salt, which causes rapid gelation by electrostatic cross-linking.  A similar process can be used to make "chunks" of everything from cat food through "reformed" ham or fish to "fruit" pieces for pies. It has the E-number 401.

Nowadays, it is also used in the biological experiments for the immobilization of cells to obtain important products like alcohols, organic acids, etc.

In recent years, sodium alginate has been used in molecular gastronomy at some of the best restaurants in the world. Ferran Adria pioneered the technique, and it has since been used by chefs such as Grant Achatz and Heston Blumenthal. Sodium alginate is combined with calcium lactate or similar compound to create spheres of liquid surrounded by a thin jelly membrane. 

Potassium alginate is a chemical compound that is the potassium salt of alginic acid. It is an extract of seaweed. Its empirical chemical formula is KC6H7O6.

Potassium alginate is widely used in foods as a stabilizer, thickener, and emulsifier.

Its use as a pharmaceutical excipient is currently limited to experimental hydrogel systems. The viscosity, adhesiveness, elasticity, stiffness, and cohesiveness of potassium alginate hydrogels have been determined and compared with values from a range of other hydrogel-forming materials. The effect of calcium ions on the rheological properties of procyanidin hydrogels containing potassium alginate and intended for oral administration has also been investigated.



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