Carboxymethyl Cellulose (CMC)
Also known as Cellulose Gum
What is Carboxymethyl Cellulose?
Carboxymethyl cellulose (CMC) is a sodium salt derivative of cellulose. Unlike cellulose, it is water soluble and can function as a suspending agent, stabilizer, film former or thickening agent.
CMC finds use in gluten-free baking by providing dough with viscosity and bread with volume much like gluten proteins do. It also functions well in fillings as a thickener and in glazes as an agent to slow down sugar crystallization.
Jansen1 first discovered carboxymethyl cellulose at the end of World War I. It was initially proposed as a substitute for naturally occurring gums. Commercial production of carboxymethyl cellulose occurred closer to World War II.
Carboxymethyl cellulose can provide different functionality depending on its degree and uniformity of substitution by sodium ions, chain length and cellulose backbone. For example, CMC with uniform substitution is known for smooth flow properties and works well in frostings. CMC with non-uniform substitution is known to be thixotropic, forms a stable gel that becomes more fluid when agitated and reforms to a gel over time. Non-uniform substituted CMC works well in fillings or sauces.2
The degree of substitution (D.S.) for sodium carboxymethyl cellulose can be up to 3, but for food application the D.S. is typically between 0.6-0.95.3
CMC is derived from cellulose, the linear glucose based polymer found in plant material. Producing CMC is a two step process. In the first step, cellulose is suspended in an alkaline solution which opens the cellulose chains and allows water to enter. When this happens, the cellulose can react with sodium monochloroacetate and yield sodium carboxymethyl cellulose.2
Some baked good applications where carboxymethyl cellulose finds use include:
- Frozen dough: As a 0.5% replacement for wheat flour and with a D.S. of 1.1, CMC weakens the influence of frozen treatment on the gluten starch structure of the dough.3
- Tortillas: CMC is added to tortillas for shelf life extension and to maintain a pliable texture.
- Gluten free bread and cakes: Improves the internal structure like gluten proteins and helps with moisture retention and mouthfeel.
- Fried doughs: At the level of 0.35%, CMC can reduce oil absorption and improve the texture of fried products.4
- Cookies: CMC functions as a release aid and spread controller.4
CMC has a tendency to lump when added to an application unless carefully mixed. Methods of addition to recipes include:2
- Adding directly to a vortex of vigorously agitated body of water.
- Dispersing CMC in another dry ingredient before adding water.
- Dispersing CMC in a water miscible non-solvent (such as glycerine or corn syrup) before adding water.
In the United States, sodium carboxymethyl cellulose is affirmed as a Generally Recognized as Safe (GRAS) as a multi-purpose food substance under the following conditions:
- Not less than 99.5% on a dry-weight basis, with a maximum substitution of 0.95 carboxymethyl groups per anhydroglucose unit, and with a minimum viscosity of 25 centipoises for 2 percent by weight aqueous solution at 25 °C.
- The ingredient has no limitations other than Good Manufacturing Practices. (21 C.F.R. § 182.1745 2018)