Denaturation of proteins.
This refers to the loss of the three dimensional functional structure of the protein.
Some instances involving denaturation of proteins.
Tenderising meat during cooking.
Curdling of milk on addition of common salt.
Solidification of the egg on boiling.
Coagulation of blood during mechanical stress.
Rigor Mortis
All the above distrupts the bonding in the protein structure destroying their functionality.