Saturday, December 10, 2011

Chemistry Saturday: Cis and trans fats

Original post can be found here...

When we have a double bond on a fatty acid, it can be in either the cis- or trans- configuration. What exactly does this mean?

In the cis configuration, the missing hydrogen atoms are on the same side of the double bond (cis means "same"). The molecules bend at the site of the double bond, giving us a kinky molecule that won't pack in nice straight, dense lines like the saturated fatty acids. Put a bunch of these together and you have a liquid oil!

In the trans configuration, the missing hydrogen atoms are on the opposite sides of the double bonds. The chain doesn't bend much, so they have a straighter shape. Meaning they can pack in more densely, resulting in an oil that behaves as a solid saturated oil instead of a liquid oil. It has a higher melting point, doesn't need refrigeration, and is cheaper than saturated oils like coconut or palm oil.

The process of partial hydrogenation can force the hydrogen atoms in a normal cis configuration to become a trans configuration. The double bonds are broken, then re-formed in the trans configuration. I think you can see why trans fats would be so popular with the food manufacturers, eh? It means you can get an oil - say, sunflower oil - that behaves like a butter by being solid and has a longer shelf life. 

If you're really interested in learning more about trans fats, please click here. It is a fascinating subject!

Join me tomorrow for a post on on functional groups, then it's back to essential oils! 

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