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Food additive of sodium carboxymethyl cellulose

2021-05-17

Sodium carboxymethyl cellulose (CMC) is a carboxymethylated cellulose derivative known as cellulose gum and is the most critical ionic cellulose gum.

CMC is usually an anionic polymer compound prepared by reacting natural cellulose with caustic alkali and monochloroacetic acid. The molecular weight of the compound ranges from several thousand to one million. The unit structure of the molecule is shown in the figure.

CMC is a modification of natural cellulose. At present, the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) have officially called it "modified cellulose." The synthesis method of sodium carboxymethyl cellulose was invented by the German E. Jansen in 1918 and was granted a patent in 1921 and was seen in the world. Since then, commercial production has been realized in Europe.

CMC was only a crude product at that time, used as a colloid and adhesive. From 1936 to 1941, the industrial application research of sodium carboxymethyl cellulose was very active, and several instructive patents were published. During the Second World War, Germany used CMC in synthetic detergents as an anti-redeposition agent. And as a substitute for some natural gums (such as gelatin, gum arabic), the CMC industry has significantly been developed.

The American Hercules company started the industrial production of CMC in 1943 and produced refined sodium carboxymethyl cellulose products in 1946, which was recognized as a safe food additive.

CMC has many unique properties, such as thickening, bonding, film formation, water retention, emulsification, suspension, etc., and it is non-toxic, odorless, challenging to ferment. Good thermal stability, so it is widely used in petroleum and geology. , Daily chemical, food, medicine, and other industries, known as "industrial monosodium glutamate."

Structural characteristics of CMC

CMC is a white or slightly yellow powder, granular or fibrous solid. It is a macromolecular chemical substance that can absorb water and swell. When swelled in water, it can form a transparent viscous glue. The pH of the water suspension is 6.5-8.5. The substance is insoluble in organic solvents such as ethanol, ether, acetone, and chloroform.

Solid CMC is relatively stable to light and room temperature and stored for a long time in a dry environment. CMC is a kind of cellulose ether. It is usually made of short cotton linter (with a cellulose content of up to 98%) or wood pulp as the raw material, processed by sodium hydroxide, and then reacted with sodium monochloroacetate. The molecular weight of the compound is 6400 (± 1000). There are usually two preparation methods: the coal-water method and the solvent method. There are also other plant fibers used to make CMC.

The functional characteristics and application of CMC

CMC is a good emulsion stabilizer and thickener in food applications and has excellent freezing and melting stability, and can improve the flavor of the product and extend the storage time.

In 1974, the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) approved pure CMC for food after rigorous biological and toxicological studies and experiments. The international standard safe intake (ADI) is 25mg/ kg body weight/day.

2.1 Thickening and the emulsification stability

Eating CMC can play a role in emulsifying and stabilizing beverages containing oil and protein. This is because CMC becomes a transparent, stable colloid after being dissolved in water, and protein particles become uniformly charged particles under the protection of the colloidal membrane, which can put the protein particles in a stable state. It also has a specific emulsification effect, so at the same time, it can reduce the surface tension between fat and water and make the fat fully emulsified.

CMC can improve the stability of the product. This is because when the pH of the product deviates from the isoelectric point of the protein, the sodium carboxymethyl cellulose can form a composite structure with the protein, which can improve the stability of the product.

2.2 Increase bulkiness

Using CMC in ice cream can increase the swelling degree of ice cream, improve the melting speed, give a good shape and taste, and control the size and growth of ice crystals during transportation and storage. The use amount is 0.5% of the total Proportioning to add.

CMC has good water retention and dispersibility and organically combines protein particles, fat globules, and water molecules in the colloid to form a uniform and stable system.
2.3 Hydrophilicity and rehydration

Such functional properties of CMC are generally used in bread production, which can make honeycomb uniform, increase volume, reduce slag, and have the function of heat preservation and freshness; CMC-added noodles have good water retention, cooking resistance, and good taste.

The molecular structure of CMC determines this. It is a cellulose derivative. There are many hydrophilic groups in the molecular chain: -OH groups and -COONa groups. Therefore, CMC has better hydrophilicity than cellulose. And water holding capacity.

2.4 Gelation

Thixotropic CMC refers to a certain number of interactions between macromolecular chains, forming a three-dimensional structure. After the three-dimensional structure is created, the viscosity of the solution increases. After the three-dimensional structure is broken, the viscosity performance decreases. The thixotropy phenomenon is that the apparent viscosity changes depend on time.

The thixotropic CMC plays an essential role in the gelling system and can be used to make jelly, jam, and other foods.

2.5 Can be used as a clarifying agent, foam stabilizer, increase taste

CMC can be used to produce alcohol to make the mouth feel more mellow, rich, and long-lasting; in beer production, it can be used as a foam stabilizer for beer to push the foam rich and lasting and improve the taste.

CMC is a kind of polyelectrolyte. It may participate in the reactions that maintain the balance of the wine body in the wine. At the same time, it combines with crystals to change the structure of the crystals and change the conditions of the crystals in the wine, causing the coagulation of the residue.

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