That the dairy products contained no G–L bond could support such an idea, because milk itself does not contain any intrinsic TGase. Besides the intrinsic TGase, heating has been reported to induce the formation of the G–L bonds due to chemical dehydration between the γ-carboxyl group of glutamate residues and ε-amino group of lysine residues. Thus, in the presence of TGase, cooking itself results in G–L formation in proteins. In this respect, mankind has been ingesting the G–L moiety since the discovery of fire and cooking. Consequently, the safety of the G–L moiety is supported by the long-term consumption of the G–L moiety in cooked foods.