Acetaldehyde is naturally present in fruits (especially apples, citrus, and grapes), dairy products (yogurt signature aroma), and fermented beverages, where it contributes to characteristic fresh-fruity top notes. Commercially it is produced by partial oxidation of ethanol or by Wacker oxidation of ethylene. In food flavor applications it is a key building block in orange, apple, raspberry, strawberry, grape, and yogurt flavor systems at extremely low use levels (typically 0.1–50 ppm).
Due to its high volatility (bp 20.2°C) and reactivity it is normally supplied chilled and handled as a diluted preparation in carrier solvents (ethanol, propylene glycol, triacetin). Acetaldehyde is FEMA GRAS 2003, listed under FDA 21 CFR 182.60 as a natural flavoring, and approved in the EU Flavoring Regulation 1334/2008. Industrial (non-food) applications include production of acetic acid, pentaerythritol, and pyridine derivatives.