Stearic acid (first syllable pronounced either steer or stair) is the saturated fatty acid with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula is CH3(CH2)16CO2H. Its name comes from the Greek word στ?αρ ("stéatos", which means tallow. The salts and esters of stearic acid are called stearates. Steric acid is noteworthy as the most common saturated fatty acid, another common one being the C16 compound palmitic acid.
It occurs in many animal and vegetable fats and oils, but it is more abundant in in animal fat (up to 30%) than vegetable fat (typically <5%). The important exceptions are cocoa butter and shea butter where the stearic acid content (as a triglyceride) is 28–45%.[2]
Stearic acid is prepared by treating these fats and oils with water at a high pressure and temperature (above 200 °C), leading to thehydrolysis of triglycerides. The resulting mixture is then distilled.[3] Commercial stearic acid is often a mixture of stearic andpalmitic acids, although purified stearic acid is available.
In terms of its biosynthesis, stearic acid is produced from carbohydrates via the fatty acid synthesis machinery via acetyl-CoA.