How does BHT delay rancidity in foods?

Butylated hydroxytoluene (BHT) is a synthetic phenolic antioxidant used to preserve fats and oils in food by delaying the process of autoxidation.12

Autoxidation is a chain reaction that degrades fat molecules through the formation of free radicals—electrically neutral molecular fragments with unpaired electrons—which eventually leads to [rancidity]. BHT functions as a free radical scavenger. It terminates this oxidative chain reaction by reacting with the chain carriers and donating hydrogen atoms, thereby preventing the degradation of fats into volatile aldehydes, ketones, and acids that cause rancidity.23

It is important to note that BHT is distinct from Bacillus thuringiensis (Bt), a soil-dwelling bacterium used as an insecticide or in genetically modified crops; the two should not be confused despite the similarity in their abbreviations. The use of antioxidants like BHT in food is strictly regulated in most countries to ensure safety.42