Interesterification is a chemical reaction that induces the rearrangement of fatty acid within and between triacylglycerols. Interesterification of oil changes its molecular composition to achieve following characteristics.
- Modify the melting point
- Slow down rancidity
- Make an oil more suitable for deep frying
- Make margarine with food taste and low saturated fat content.
Interesterification can be classified into following types.
- Chemical Interesterification
- Enzymatic Interesterification
Chemical Interesterification: treating oil and fat with sodium methoxide as catalyst at 80°C causes intermolecular ester exchange as a result, oil changes its physical properties such as melting point and consistency. The ester exchange result random and nonselective rearrangement of fatty acid.
Enzymatic Interesterification: enzymatic interesterification is done in industry for selective modification of fatty acids.
An important application of interesterification is improvement of natural lard. Natural lard tends to form a rough crystal which is difficult to handle during storage. This is because 64 % of palmitic acid is attached to second position of triglycerol molecules. Randomizing the positional distribution of fatty acids of natural lard by interesterification improves its physical property, making it smooth.
Another example of interesterification is in the field of margarine production. Interesterification of soybean oil to completely hydrogenated soybean oil provides material for margarine. This rearranged oil has an advantage that it does not contain Trans-fatty acid because it is not made through partial hydrogenation.