Glycerol or Glycerin: Is there a difference?

The terms "glycerin" and "glycerol" are used almost interchangeably, yet there is indeed a difference between these two concepts. Although they share the same chemical compound (C3H8O3), they are not as similar as one might think.

Glycerol.

Glycerol, a purified molecule of glycerine, refers to an organic polyol compound in its pure form, directly present in the triglycerides of fats and oils. It is a three-carbon alcohol metabolite covalently linked to a hydroxyl group, which resembles a sugar and, at room temperature, is syrupy. It is a highly hygroscopic, viscous, odorless, transparent fluid with a mild sweet taste and non-toxic at low concentrations. There are three distinct processes used to produce glycerol.

1. Through the complete synthesis of propylene via several pathways;

2. Through the process of trans-esterification of oils or fats;

3. Through alcoholic fermentation with yeasts (Saccharomyces cerevisiae, Candida) and bacteria (Bacillus subtilis).

Glycerol is commonly used in a number of industrial applications, and can be taken orally as well as applied to the skin. In the food industry, it is used as a solvent, sweetener, humectant, and preservative. It is also used in the manufacture of nitroglycerin for the production of explosives. Due to its chemical properties, glycerol is included in antifreeze and anti-icing liquids. In the pharmaceutical field, it is used in the treatment of cerebral edema, respiratory disorders, as a laxative (suppositories), as well as in cough syrups (expectorants).

Glycerin.

The glycerin is the commercial name for glycerol and a by-product of industrial-scale biofuel production from oils or fats. It is a solution with over 95% glycerol and contains impurities in the form of methanol, water, salts, and free fatty acids. It has the same properties as glycerol. It is hygroscopic, virtually colorless, with diuretic and laxative osmotic effects. As a chemical compound, glycerin is a trihydroxy sugar alcohol. It shares the same chemical molecule with glycerol, propane-1,2,3-triol (HOH2C–CHOH–CH2OH), but glycerin is less pure. There are three extraction processes to obtain glycerin.

One of these is the hydrolysis of lipids, where oils are subjected to the combined force of pressure, temperature, and water. The glycerin separated from the fatty acids is absorbed by the water. Another solution is the trans-esterification (alcoholysis) of triglycerides contained in an oil/fat combined cold with an alcohol (ethanol or methanol). This method produces ethyl or methyl esters and glycerin with a high glycerol content. Finally, the saponification of fats and a caustic alkali (lye or potash) produces glycerin (about 20%) and a mixture of carboxylates, which constitutes soap. The glycerin is widely used in cosmetics to hydrate the skin, improve barrier function and the mechanical properties of the skin, accelerate the healing process, and protect the skin from irritations.