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| Names | |
|---|---|
| Other names Carboxymethylcellulose; carmellose; E466 | |
| Identifiers | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| ECHA InfoCard | 100.120.377 |
| E number | E466(thickeners, ...) |
| UNII | |
| Properties | |
| variable | |
| Molar mass | variable |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Carboxymethyl cellulose (CMC) orcellulose gum[1] is acellulosederivative withcarboxymethyl groups (-CH2-COOH) bound to some of thehydroxyl groups of theglucopyranosemonomers that make up thecellulosebackbone. It is often used in itssodium salt form,sodium carboxymethyl cellulose. It used to be marketed under the name Tylose, a registered trademark of SE Tylose.[2]
Carboxymethyl cellulose issynthesized by thealkali-catalyzedreaction of cellulose withchloroacetic acid.[3] Thepolar (organicacid)carboxyl groups render the cellulosesoluble and chemically reactive.[4] Fabrics made of cellulose – e.g., cotton orviscose (rayon) – may also be converted into CMC.[5]
Following the initial reaction, the resultant mixture produces approximately 60% CMC and 40% salts (sodium chloride andsodium glycolate). This product, called technical CMC, is used indetergents.[citation needed] An additional purification process is used to remove salts to produce pure CMC, which is used for food and pharmaceutical applications.[6] An intermediate 'semi-purified' grade is also produced, which is typically used in paper applications such as the restoration of archival documents.[7]
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CMC is a derivative of the regenerated cellulose [C6H10O5]n with hydroxy-acetic acid (hydroxyethanoic acid) CH2(OH)COOH orsodium monochloroacetate (Na[ClCH2COO]). The CMC backbone consists ofD-glucose residues linked by -1,4-linkage. It has carboxymethyl groups (-CH2-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone. It is often used as its sodium salt, sodium carboxymethyl cellulose.[8]
CMC is a white or lightly yellow powder with no odor, flavor, orpoisonous properties. It ishygroscopic and dissolves well in hot or cold water, forming aviscous solution. It is not soluble in organic solvents likemethanol,ethanol,acetone,chloroform, andbenzene. The functional properties of CMC depend on the degree of substitution of the cellulose structure (i.e., how many of the hydroxyl groups have been converted to carboxymethylene groups in the substitution reaction), as well as the chain length of the cellulose backbone structure and the degree of clustering of the carboxymethyl substituents. It is commonly used as a viscosity modifier or thickener and to stabilize emulsions in various products, both food and non-food-related. It is mainly used because it has a high viscosity, is nontoxic, and is generally considered to be hypoallergenic.[8]
Carboxymethyl cellulose (CMC) is used in applications ranging from food production to medical treatments.[9] It is commonly used as aviscosity modifier orthickener and tostabilizeemulsions in both food and non-food products. It is used primarily because it has highviscosity, is nontoxic, and is generally considered to behypoallergenic, as the major source fiber is either softwood pulp orcotton linter. It is also used in non-food products which include products such astoothpaste,laxatives,diet pills,water-basedpaints,detergents, textilesizing, reusableheat packs, variouspaper products, filtration materials, synthetic membranes, wound healing applications, and also in leather crafting to help burnish edges.[10][11][12][verification needed]
CMC is registered as E466 or E469 (when it isenzymatically hydrolyzed). It is used for aviscosity modifier orthickener and tostabilizeemulsions in various products, includingice cream, mayonnaise, and beverages. It is also used extensively in gluten-free and reduced-fat food products.[13]
CMC's variable viscosity (high while cold, and low while hot) makes it useful in the preparation of cold foods and textures in beverages and edible gels. With a DS around 1.0, it can prevent dehydration and shrinkage of gelatin while also contributing to a more airy structure. In some foods, it can be used to control oil and moisture content.[14]
CMC is used to achievetartrate or cold stability in wine, which can prevent excess energy usage while chilling wine in warm climates. It is more stable thanmetatartaric acid and is very effective in inhibiting tartrate precipitation. It is reported thatKHT crystals, in the presence of CMC, grow slower and change their morphology.[15][non-primary source needed][16][17][better source needed] Their shape becomes flatter because they lose 2 of the 7 faces, changing their dimensions. CMC molecules, negatively charged at wine pH, interact with the electropositive surface of the crystals, where potassium ions are accumulated. The slower growth of the crystals and the modification of their shape are caused by the competition between CMC molecules and bitartrate ions for binding to the KHT crystals.[18][17]
CMC is a common ingredient in cleaning products because of its thickening and stabilizing properties and nontoxic composition. In detergent and cleaning products, it can be used to enhance texture and assist in the suspension of dirt and grime in the cleaning product. Its adjustableviscosity can be used to standardize the textures of the products, especially when used along with other chemicals.
CMC helps with the removal of grease and aids in the creation of small bubbles in the soap. This, along with its ability to suspend dirt in mixtures, can make soaps and other cleaning products more efficient.[20]
CMC is used in textiles as a thickening agent in textile printing, constituting about 2-3% of printing pastes. It is also used in fabric finishing to affect the fabric's texture. Additionally, CMC serves as a binding agent in non-woven fabrics, contributing to the strength and stability of the material. In sizing applications, about 1-3% of CMC is used to protect yarns during weaving to reduce breakages.
CMC aids in thickening printing pastes, which makes the prints themselves more precise. It is also used to thicken dyes. Additionally, it is an alternative to synthetic thickeners.[21]
CMC is an ingredient used in over 50% of cosmetic products. As a thickening agent, it is used in formulations where viscosity needs to be precisely controlled. In hair care, about 25% of shampoos and conditioners utilize CMC for its conditioning and detangling effects. It is also used in the makeup and toothpaste industries to control the products' texture. Due to its ability to retain moisture, it is also used in skincare products. CMC serves as a film-forming agent in approximately 10% of sunscreens.
CMC aids in pigment suspension and dispersion, binding other ingredients for even distribution. CMC, when combined with Fatty Acid Ethanolamine or 2,2'-Iminodiethanol in a hair product, can form a thin film around the hair.[22]
CMC powder is widely used in the ice cream industry, to make ice creams without churning or extremely low temperatures, thereby eliminating the need for conventional churners or salt ice mixes.[23] CMC is used in baking breads and cakes. The use of CMC gives the loaf an improved quality at a reduced cost by reducing the need for fat. CMC is also used as an emulsifier in biscuits. Dispersing fat uniformly in the dough improves the release of the dough from the molds and cutters, achieving well-shaped biscuits without any distorted edges. It can also help to reduce the amount of egg yolk or fat used in making the biscuits. The use of CMC in candy preparation ensures smooth dispersion in flavor oils and improves texture and quality. CMC is used in chewing gums, margarine, and peanut butter as an emulsifier.[24]
CMC is also used in numerous medical applications.[9][12][25][26]
Some examples include:
Inophthalmology, CMC is used as a lubricating agent inartificial tears solutions for the treatment of dry eyes.[30]
In veterinary medicine, CMC is used in abdominal surgeries in large animals, particularly horses, to prevent the formation of bowel adhesions.[31]
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Insoluble CMC (water-insoluble) can be used in the purification of proteins, particularly in the form of charged filtration membranes or as granules in cation-exchange resins forion-exchange chromatography.[32] Its low solubility is a result of a lower DS value (the number of carboxymethyl groups per anhydroglucose unit in the cellulose chain) compared to soluble CMC.[33] Insoluble CMC offers physical properties similar to insoluble cellulose, while the negatively charged carboxylate groups allow it to bind to positively charged proteins.[34] Insoluble CMC can also be chemically cross-linked to enhance the mechanical strength of the material.[35]
Moreover, CMC has been used extensively to characterize enzyme activity from endoglucanases (part of thecellulase complex); it is a highly specific substrate for endo-acting cellulases, as its structure has been engineered to decrystallizecellulose and create amorphous sites that are ideal for endoglucanase action.[citation needed] CMC is desirable because the catalysis product (glucose) is easily measured using areducing sugar assay, such as3,5-dinitrosalicylic acid.[citation needed] Using CMC in enzyme assays is especially important in screening for cellulase enzymes that are needed for more efficientcellulosic ethanol conversion.[citation needed] CMC was misused in early work with cellulase enzymes, as many had associated whole cellulase activity with CMC hydrolysis.[according to whom?] As the mechanism of cellulose depolymerization became better understood, it became clear that exo-cellulases are dominant in the degradation of crystalline (e.g. Avicel) and not soluble (e.g. CMC) cellulose.[citation needed]
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In laundry detergents, it is used as a soil suspension polymer designed to deposit onto cotton and other cellulosic fabrics, creating a negatively charged barrier to soils in the wash solution.[citation needed] CMC is also used as a thickening agent, for example, in the oil-drilling industry as an ingredient ofdrilling mud, where it acts as a viscosity modifier and water retention agent.[citation needed]
CMC is sometimes used as an electrode binder in advanced battery applications (i.e.lithium ion batteries), especially withgraphite anodes.[36] CMC's water solubility allows for less toxic and costly processing than with non-water-soluble binders, like the traditionalpolyvinylidene fluoride (PVDF), which requires toxicn-methylpyrrolidone (NMP) for processing.[citation needed] CMC is often used in conjunction withstyrene-butadiene rubber (SBR) for electrodes requiring extra flexibility, e.g. for use with silicon-containing anodes.[37]
CMC is also used inice packs to form aeutectic mixture resulting ina lower freezing point, and therefore more cooling capacity than ice.[38]
Aqueous solutions of CMC have also been used to disperse carbon nanotubes, where the long CMC molecules are thought to wrap around the nanotubes, allowing them to be dispersed in water.[citation needed]
In conservation-restoration, it is used as an adhesive or fixative (commercial name Walocel, Klucel).[citation needed]
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Effects oninflammation, microbiota-relatedmetabolic syndrome, andcolitis are a subject of research.[39] Carboxymethyl cellulose, along with other emulsifiers, is suggested as a possible cause of inflammation of the gut,[40] through alteration of thehuman gastrointestinal microbiota, and has been suggested as a triggering factor ininflammatory bowel diseases such as ulcerative colitis andCrohn's disease.[41][42][non-primary source needed]
While thought to be uncommon, case reports of severe reactions to CMC exist.[43] Skin testing is believed to be a useful diagnostic tool for this purpose.[44]
Due to its high solubility and clarity of its solutions, CMC is commonly used in beverages and beverage dry mixes to provide rich mouthfeel. It is also used in acidified protein drinks to stabilize protein and prevent it from precipitating. CMC is also added to syrup and sauce formulations to increase viscosity.
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