Carboxymethylcellulose (OK, back to starch)
20th June 2006
Sorry to punt again but I’m just getting home. Today’s molecule is carboxymethylcellulose. It is made from cellulose by its reaction with chloroacetic acid.
The idea here is this: Water is very polar and will interact strongly with polar functional groups (i.e., hydroxyls in cellulose). It will interact very strongly with charged groups. By converting some of these hydroxyls to carboxylates, we have something a lot like starch that is more water-soluble.
Like starch, CMC can thicken aqueous solutions, and it is very slippery (most gravies are effectively a solution of starch in water - most are much more, but there are some for which this description is a bit flattering). CMC is everywhere you’d expect its properties to be remotely useful, because cellulose is so abundant and cheap. Wikipedia says it best:
CMC is used in food science as a viscosity modifier or thickener, and to stabilize emulsions, for instance in ice cream. It has E number E466. It is also a constituent of many non-food products, such as K-Y Jelly, toothpaste, laxatives, diet pills, water-based paints, detergents, and various paper products. They have high viscosity, are not toxic, and are generally non-allergenic. CMC is used as a lubricant in non-volatile eye drops (artificial tears).
From ice cream to lubricant to paint. Every molecule should be so versatile.
See you tomorrow.