Yogurt gets its buttery aroma from diacetyl, the same compound used to scent movie theater popcorn.

Diacetyl, also known as 2,3-butanedione, is a natural byproduct of the fermentation process in dairy products like yogurt, butter, and cultured cream. In yogurt production, lactic acid bacteria such as Lactobacillus bulgaricus and Streptococcus thermophilus convert lactose into lactic acid. However, secondary metabolic pathways involving citrate metabolism produce diacetyl, which provides the characteristic 'buttery' flavor profile.The food industry has utilized this organic compound for decades to mimic the taste of butter in products like margarine and microwave popcorn. In the early 2000s, the National Institute for Occupational Safety and Health (NIOSH) investigated diacetyl due to health concerns for factory workers who inhaled large quantities of the concentrated vapor. This led to the identification of 'popcorn lung,' a serious respiratory condition formally known as bronchiolitis obliterans.Despite these industrial inhalation risks, the U.S. Food and Drug Administration (FDA) classifies diacetyl as 'Generally Recognized as Safe' (GRAS) for ingestion. In a typical serving of yogurt, the concentration of diacetyl is very low, usually ranging from 0.5 to 5 milligrams per kilogram. This small amount is sufficient to trigger human olfactory receptors, which are highly sensitive to the molecule's distinct chemical structure.