The release of water molecules during the condensation of fats is a result of a chemical reaction called esterification. Fats are composed of molecules known as triglycerides, which consist of three fatty acid molecules attached to a glycerol molecule.
During the condensation reaction, the hydroxyl (-OH) group of the glycerol molecule reacts with the carboxyl (-COOH) group of a fatty acid molecule. This reaction involves the removal of a water molecule (H₂O) and the formation of an ester bond:
Glycerol + Fatty Acid → Ester + Water
This reaction occurs three times, as there are three fatty acid molecules in a triglyceride. Each esterification reaction between a fatty acid and the glycerol molecule results in the release of one water molecule. Consequently, a total of three water molecules are released when the three fatty acids are condensed with glycerol to form a triglyceride.
This process is known as a dehydration synthesis reaction or a condensation reaction because water is formed as a byproduct during the synthesis of the larger triglyceride molecule.