Re: Which has more lipids castor oil or coconut oil?

Hi Shubham,

Your question points out a flaw in the comparison you describe. When we talk about the lipid or fat content of a material, we need to have a standard system of measurement for proper comparison. A good unit of measurement would be weight percent lipids (wt%), which would be the mass of lipids in a given sample over the mass of the entire sample (mass percent would be a more correct term, but chemists and engineers tend to call this quantity weight percent). The comparison you describe doesn't seem to have ever measured how much of each oil (in grams) was spotted onto the paper.

On the other hand, the way you phrased the question makes it simple to answer on one level, and then more complex on the next level. If I said that both oils have the same lipid content, about 100 wt%, I'd be very near correct. That's pretty much what food oils are - they're mixtures of lipids.

Let's review what lipids are (see http://en.wikipedia.org/wiki/Lipid).
Lipids are greasy (hydrophobic) things that come from living organisms; things like fats, fatty acids, phospholipids which make up cell membranes, carotenoids, etc. Oils are primarily mixtures of triglycerides, which are definitely lipids (see http://en.wikipedia.org/wiki/Oil and http://en.wikipedia.org/wiki/Triglyceride). Each triglyceride molecule contains a three-carbon portion from glycerol, and three fatty acid portions. A triglyceride molecule is formed by the esterification of three fatty acid molecules with one molecule of glycerol. The three fatty acids could be identical or different.

The big difference between coconut and castor oils is in the composition of their triglycerides; that is, the identity of the different fatty acids from which they are synthesized.

This is what Wikipedia says about coconut oil (from http://en.wikipedia.org/wiki/Coconut_oil): "Coconut oil is a fat consisting of about 90% saturated fat. The oil contains predominantly triglycerides with 86.5% saturated fatty acids, 5.8% monounsaturated fatty acids, and 1.8% polyunsaturated fatty acids. Of the saturated fatty acids, coconut oil is primarily 44.6% lauric acid, 16.8% myristic acid and 8.2% palmitic acid, although it contains seven different saturated fatty acids in total. Its only monounsaturated fatty acid is oleic acid while its only polyunsaturated fatty acid is linoleic acid."

Wikipedia says the following about castor oil (from http://en.wikipedia.org/wiki/Castor_oil): "Castor oil has an unusual composition and chemistry, which makes it quite valuable. Ninety percent of fatty acids in castor oil are ricinoleic acid. Ricinoleic acid, a monounsaturated, 18-carbon fatty acid, has a hydroxyl functional group at the twelfth carbon, a very uncommon property for a biological fatty acid. This functional group causes ricinoleic acid (and castor oil) to be unusually polar, and also allows chemical derivatization that is not practical with other biological oils; Castor oil also contains 3-4% of both oleic and linoleic acids."

So even though coconut and castor oils are both basically 100% lipids, they differ greatly in the chemical nature of their lipids. This is why you observed that the two oils had different translucency.

-Alex Tobias