triglycerides? This beautiful molecule to the left is a triglyceride (castor oil to be exact). It is a molecule with a glycerol (or glycerine) backbone and three fatty acids attached to it. If you look at this molecule - around the middle, before the OH bonds - you'll see a double line. This is a double bond, which means this is an unsaturated molecule.
In a saturated triglyceride, the carbons are single bonded, which are hard to break. They are stable over long periods of time because there isn't going to be oxidation. Most of these are buttery fats like coconut oil, babassu oil, palm oil, and animal oils. Oils like beeswax and candelilla wax are also saturated (yep, I don't think of beeswax as an oil either, but it fits the description!) Jojoba is another saturated triglyceride, which explains its long shelf life.
In an unsaturated triglyceride, these double bonds can be broken easily and oxidation occurs. The more double bonds, the more potential for oxidation. This explains the shelf life of something like grapeseed oil. It has 3 double bonds in the chain (it is a C18:3 triglyceride, meaning is has 18 carbon bonds and 3 double bonds), which means it has three places where the bonds can be broken and the oxidation can occur!
Which fatty acids might we find in our oils? When you look at the code after the name of the fatty acid, this is how to translate it...The C means the number of carbons in the chain, the number is the number of carbons and the number after the colon - if there is one - is the number of double bonds in the chain. If there is no colon, it means there are no double bonds, and that indicates a saturated fatty acid. If there is a number after the colon, it means this is an unsaturated fatty acid with 1 or 2 or 3 or 4 double bonds, depending on the number. So oleic acid (C18:1) is an unsaturated fatty acid that has one double bond.
- caprylic acid (C8)
- capric acid (C10)
- lauric acid (C12)
- myristic acid (C14)
- palmitic acid (C16)
- stearic acid (C18:0)
- oleic acid (C18:1)
- linoleic acid (C18:2)
- linolenic acid (C18:3)
- arachadonic (C20:4)
So an saturated fatty acid is one that has no double bonds and lies straight. It should have a longer shelf life than an unsaturated fatty acid with double bonds that doesn't lie straight. The more saturated the fatty acids, the stiffer the product tends to be. For instance, coconut oil is filled with saturated fatty acids while olive oil has really low levels. We'd expect the coconut oil to be a stiffer or more solid product than the olive oil (which it is).
Related posts (and I really encourage you to check these out for this series...)
Hydrogenation and fatty acid shapes
Cis and trans fats
Join me tomorrow as we review polyphenols and phytosterols!