In chemistry, a compound formed during a multi-step reaction that is then consumed in a subsequent step to produce the final product. Intermediates may be stable enough to isolate or so short-lived that they exist only fleetingly. In food chemistry, many flavour and colour developments proceed through intermediates: the Maillard reaction between amino acids and sugars generates a cascade of intermediate compounds before forming brown melanoidin pigments and roasted aromas. Lipid oxidation likewise passes through hydroperoxide intermediates before breaking down into the aldehydes responsible for rancid off-flavours. Understanding intermediates helps food scientists control processing, predict shelf life, and design reactions that favour desirable outcomes.