The structure of fermented milk products is influenced to a large extent by the properties of the milk proteins. One way to influence this is via the enzymatic modification of proteins, more specifically protein crosslinking. An extensively studied enzyme is microbial transglutaminase (glutaminylpeptide:amine g-glutamyltransferase, EC 2.3.2.13, MTGase) which crosslinks glutamine and lysine residues in milk proteins.