Chemistry of Oils (part 2)- Fatty Acids

Wednesday, 26 August 2015

Hi all, this post is an extension of part 1 chemistry of oil; which was all about introduction of what double bond is and how it gets rancid. In today's post i will go further in-depth about the fatty acids that eventually makes up to triglycerides (oils/Carrier Oil)

So what exactly are fatty acids?
Fatty acids are basically molecules that contains 12-24 carbon groups that combines with each other to form a triglyceride (layman term: Oils and butters)

Now a lot of you may know what stearic acid is. Its used in may products especially in soap to make it harder, and in lotion to make it thicker.
Stearic Acid Molecule
Now below is how a stearic acid looks like. its a fatty acid chain thats straight with no double bonds at all. Usually to form a triglycerides, there will be a combination of few fatty acids, but just imagine if the triglycerides only had stearic acid as the fatty acids, imagine how stable the oil will be! but in the real world there is no such oil that exists. Hence the reason i would like to introduce you to all the other common fatty acids in the world to you:

Below are the common fatty acids and its carbon and bond looks like:

Confused yet?
Now take a look at the carbon bond for each. Look at the saturated fatty acid. None of them have got any double bonds. hence its written as 12:0, 14:0 and so on. As for the unsaturated fatty acids look at 16:1 Palmitoleic acid. It basically means that this fatty acid has a 16 carbon bond and one double bond. Individually it doesn't make sense so let me show you when its all put together:
we will compare two oils in this comparison.

1) Olive Oil
Palmitic Acid-->10.5%
Stearic Acid----> 2.6%
Oleic Acid------> 55-83%
Linoleic Acid--->4-21%

2) Grape Seed Oil
Palmitic Acid-->7%
Stearic Acid---->4%
Oleic Acid------> 16%
Linoleic Acid---> 72%

So for the purpose of comparison, look at the saturated fatty acid and unsaturated fatty acid both the oils has. Olive oil generally have gt 13.1% of saturated fat, 1 double bond fatty acid (oleic), 1 double double bond fatty acid. Grape seed on the other hand have gt lower saturated fats (11%), one double bond oleic acid, and one more double double bond linoleic acid at higher percentage.

Just by looking at this structure one can figure out that because grape seed oil has more double bonds and double double bonds, its not a stable oil hence it gets rancid super fast at 3-6months as compared to olive oil that has a shelf life of 2-3 years.

So how does this translate to choosing oil to make body care:
This basically guides you that the next time you choose your oils, you can view its amount of saturated and unsaturated fatty acids to estimate the shelf life of your product.

Again if you have not read the first part of this post, please click here.


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