Extra virgin olive oil is obtain through purely mechanical and other physical means, and should contain no more than 0.8% free fatty acids (oleic acid), and should contain no more than 0.9% linolenic acid. Virgin olive oil should contain no more than 2% free fatty acids. Pomace and refined olive oil (once called "pure olive oil") contain no more than 0.3% fatty acids. This has little to no impact on use of oils in our creations and lotions, but it does help to define the categories of olive oil.
We know oleic acid has many great features - it's moisturizing, regenerating, softening, offers anti-inflammatory properties, and is well absorbed by the skin - but the unsaponifiables in olive oil are really vital to its awesome power!
Unsaponifiable matter is that matter which is present after an oil has been saponified or mixed with a base like sodium hydroxide or potassium hydroxide. That which is left over includes lipids of natural origin - sterols, pigments, alcohols, and so on.
In the 0.5 to 1.5% of the unsaponifiable part of olive oil we find the good stuff that gives olive oil its punch. We find the tocopherols - 100 to 300 mg per kilogram of oil - and squalene, which makes up 40 to 50%! Squalene is found in our sebum (about 12%), which is why you'll see olive oil as listed as being like our natural sebum and allowing our skin to "breathe".
I'll be going into more detail about squalene in the near future, but here's a short note...Squalene is a vital part of cholesterol and Vitamin D synthesis in our bodies. Squalene actually penetrates the epidermis quickly, and helps to soften skin well. Look at all those double bonds! Eeek! This is why you'll find squalane (notice the -ane at the end indicating there are no double bonds) in our skin care products rather than squalene.
Olive oil has 100 to 300 mg per kg of tocopherols, which retard rancidity and add Vitamin E to your creations. With all that oleic acid, its shelf life is about 1 year.
It's high in phytosterols (221 mg per 100 grams of oil) and polyphenols. The oleuropein in olive oil has been shown to help with sun damaged skin in a pure form, and studies have shown olive oil to be a fantastic oil for after sun exposure by helping to repair damaged cells and increase cell regeneration.
There is some evidence that olive oil can be detrimental to acne prone skin due to the high ratio of oleic acid, which could make the bacteria that causes acne (P. acnes) worse. And it's a humectant, which means you're adding more hygroscopic goodness to your lotions (this is due to the alcohols present in the unsaponifiables).
As a note, the polyphenols and fatty acid profile will vary with the type of olives, the region in which they are grown, the time of year they are picked, and whether you are using extra virgin olive oil or pomace. For instance, you might find 50 to 80 ppm polyphenols in extra virgin olive oil while refined oils might only contain 5 ppm. There is no significant difference in the phytosterols between types of olive oil.
It's vital to choose your olive oil with your application in mind. If you want the benefits of the polyphenols, you'll want to choose an extra virgin olive oil for your lotions. If you want the benefits of the oleic acid, then any type of olive oil should work. I tend to use pomace for my creations due to cost, and I add extra Vitamin E to retard rancidity. (Remember, I'm not a soapmaker, so I can't suggest which type to use for that application.)
To summarize - Olive oil is a medium to heavy weight oil with a shelf life of about 1 year (pomace will be lower due to the reduced polyphenols). It offers anti-inflammatory and softening benefits, and is a great addition to any lotion you might use after sun exposure.
Join me for fun formulating with olive oil tomorrow!