I thought I would do a series of blog entries on chemistry concepts that are important to the cosmetics crafter. But before we get started, if you are planning on making your products ‘chemical free’ I suggest you think otherwise. Our bodies themselves are composed of chemicals and everything we put in or on our body is composed of chemicals. With some knowledge of chemistry we can find out which of these chemicals are safe, effective and actually good for us.
Lipids could be considered the most important part of skin care products. They are able to protect the skin from water loss, helping the barrier function of the skin. Lipids are defined by their ability to be soluble in organic solvents. In general lipids are used by mammals like us for energy reserves and to form cell membranes. The main lipid category is a triglyceride, also called a triacylglycerol. Other lipids include phospholipids, steroids and essential oils (for lack of any other category to put them). We’ll focus on the triglycerides alone though.
The structure of a triglyceride is a glycerol molecule as a backbone with three fatty acids attached to that. Since glycerol is a three carbon sugar, each fatty acid can bond to one of the carbons. Glycerine is also an alcohol as defined by the –OH groups.
Below is a triglyceride. You can see the three carbon glycerin portion of the molecule on the left and the fatty acid chains to the right. Using this type of connotation each bend of the line represents a carbon atom.
Fatty acids are long chain hydrocarbons and identified by the number of carbons in their chain as well as by the number and placement of double bonds.
In this figure the first fatty acid from the top has16 carbons with no double bond. This fatty is abbreviated 16:0 and called palmitic acid. This fatty acid is saturated meaning that there are no double bonds in the chain. Each carbon atom is bonded to two hydrogen atoms (not shown) so the carbons are saturated with hydrogens.
The second fatty acid from the top has 18 carbons and one double bond. This is abbreviated 18:1 and is called oleic acid. Notice too that the double bond is at the ninth carbon.
The third fatty acid chain has 18 carbons again but three double bonds. This is abbreviated 18:3 and is referred to as alpha linolenic acid. This is an omega-3 fatty acid which refers to the fact that it has a double bond 3 carbons from the omega end of the chain.
So each different oil or fat you use in skin care is made up of triglycerides. Triglycerides found in different oils have different fatty acids associated with them which is referred to as the fatty acid profile. Various fatty acids can have different properties for skin care, a topic for another blog.