2-Acetyl-5-(1,2,3,4-tetrahydroxybutyl)-1H-imidazole (THI) is a heterocyclic compound primarily known as an impurity in Class III caramel colorants used in food and beverage industries. It is formed during the production of caramel coloring through the Maillard reaction. THI is studied for its biological activity, particularly its ability to bind to thiamine (vitamin B1), potentially causing thiamine deficiency and associated health effects. This has led to regulatory limits on its levels in food additives. In research, it is used to investigate toxicology, nutrition, and metabolic processes, with some studies exploring its potential antioxidant and anti-inflammatory properties.