By Yusra Hashim
There are two ways to classify fat, the first way depends on the saturation of the fatty acids it composed and the second depends on the size of its fatty acid.
Fat is an organic substance formed of a collection of molecules called triglyceride.
What is triglyceride? It is a molecule made of a single glycerol and three fatty acid molecules. Glycerol is the same in all types of fat, if it is from plant or animal sources.
Fatty acid is formed of carbon, hydrogen and oxygen .The carbon atoms form a chain, the difference in the length of this chain form the different properties of the fat molecule. Hydrogen atoms attach to this carbon chain and the carboxyl (acid) group to the end of each chain.
As carbon atoms can make four bonds with other atoms, each carbon atom in the middle attach to two hydrogen atoms and the other two attach to the neighbouring carbon atoms in the chain.
Classification of fat
According to the maturity level of the fatty acids there are three types of fat;
This type has got all carbon atoms saturated by hydrogen and there is no double bond. The shape of the fatty acid is straight allowing packing of the molecules, which keep the oil solid in higher temperature than that for unsaturated fat. Saturated fat is less likely to go rancid and forming free radicals. it is the best oil for cooking .
We said that fatty acids are composed of a carbon chain with attached hydrogen .So what happens if one or two of the hydrogen atoms are missing?
The free electrons will bind together forming double bond between two carbons. This double bond will make the fatty acid unsaturated . There are two types of unsaturated fatty acid;
Like The fatty acid oleic which form 71% of olive oil contains one double bond .This double bond makes a slight bend in the structure of the fatty acid which affects the packing together of the fatty acids and makes the oil liquid in room temperature but could become solid in the refrigerator.
The fatty acid forming this oil has more than one double bond. This type of oil is in liquid form even in the refrigerator. This level of unsaturation makes the oil highly reactive and risky in forming dangerous free radicals if exposed to heat, oxygen and light. This makes it the worst oil to cook with .e.g. Linoleic acid, 2 double bonds (omega 6) and Linolenic acid (omega 3) which has three double bonds.
The omega number indicates the position of the first double bond not the number of the double bonds). Processed polyunsaturated fats include; corn, soy and safflower oil.
The second method of fat classification
This depends on the length of the carbon chain forming the fatty acid, there are three types of fat;
Short chain fatty acids (SHFA), composed of less than 8 carbons.This include Propionic acid (3 carbons), butyric acid (4 carbons) and caproic acid (6 carbons). SHFA are always saturated.
All fat present as triglycerides and the type of fat depends on its fatty acids type. So SCFA is also called short chain triglyceride (SHT) and medium chain fatty acid or medium chain triglyceride.
Medium chain fatty acid (MCFA)
These fatty acid contains 8-12 carbon atoms .they are saturated fatty acids include Caprylic acid (8 carbons), Capric (10 carbons), and Lauric acid (12 carbon atoms). Coconut oil is the richest fat of this nutritional and medicinal type of fatty acid. Palm kernel oil and butter also have MCFA.
Long chain fatty acids (LCFA)
These fatty acids contain 14 or more carbon atoms in their fatty acid chain, almost all oils in our food are long chain fatty acids e.g. soybean oil, corn oil, canola oil, olive oil, lard and chicken fat.