Diacetyl (Dia)

Diacetyl is an organic compound with the chemical formula (CH3CO)2. It is a volatile, colourless liquid with an intensely buttery flavor. It is a vicinal diketone with the molecular formula C4H6O2. Diacetyl occurs naturally in alcoholic beverages and is added to some foods to impart its buttery flavor. Diacetyl is produced by dehydrogenation of 2,3-butanediol. Acetoin is an intermediate. It arises naturally as a byproduct of fermentation. In some fermentative bacteria, it is formed from by thiamine pyrophosphate-mediated condensation of pyruvate and acetyl CoA. Sour (cultured) cream, cultured buttermilk, and cultured butter are produced by inoculating pasteurized cream or milk with a lactic starter culture, churning (agitating) and holding the milk until a desired pH drop (or increase in acidity) is attained. Cultured cream, cultured butter, and cultured buttermilk owe their tart flavour to lactic acid bacteria and their buttery aroma and taste to diacetyl.