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In nature  triglycerides are composed of a glycerin molecule bound to three acid chains. These acids are fatty acids i.e. they are made out of fats. Vegetable oils and animal fats are both examples of triglycerides.

Glycerine bound to three fatty acid


Glycerides can be saturated in which case they tend to be solid at room temperature, fat from an animal is highly saturated.  An oil like canola of sunflower is mostly unsaturated  and tends  to be more liquid at normal temperatures. There are vegetable oils like palm and coconut which are saturated and also tend to be solid at room temperature.

When a person eats food, excess calories are stored in triglycerides. A high concentration of in your blood indicates the consumption of starches and carbohydrates. Elevated levels in your blood stream can be an indication of raised risk of heart disease.


The  biodiesel  process takes a triglyceride and breaks the fatty acid bond with the glycerin molecule using lye (caustic soda) or potassium hydroxide. Once the fatty acid has broken off the glycerin,  it bonds with a molecule  of methanol and forms a biodiesel molecule.  After this process we are left with a Diglyceride and a biodiesel molecule.

Glycerine bound to two fatty acid = Diglyceride


A diglyceride has two fatty acids which are still bonded to the glycerin molecule. In the biodiesel process  another fatty acid is removed and is bonded to a methanol molecule. This results in a monoglyceride and we now have two biodiesel molecules.

Glycerine bound to one fatty acid = Monoglyceride


A monoglyceride has one fatty acid which is still bonded to the glycerin molecule. In the biodiesel process  this fatty acid is removed and bonded to a methanol molecule. This results in a free glycerin molecule and we now have a total of three  biodiesel molecules.


Glycerine not bound to any fatty acids drops out of the biodiesel.


Technically oil is an ester of glycerin and fatty acids; biodiesel is an ester of methanol and fatty acids. The technical term for biodiesel is fatty acid methyl ester.

The biodiesel process described above is called transesterfication and it is the process of converting oils and fats into a methyl ester (biodiesel).

It is worth mentioning that in the cooking process oil or fat breaks down due to the high temperatures into diglycerides and monoglycerides over time. This results in free fatty acids in the oil which eventually makes it toxic to humans and animals, this is the main reason that reputable restaurants will change their oil frequently.



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