Acetaldehyde is a common substance that smells like apples and is abundant in nature. Fermented foods, such as alcoholic beverages, vinegar, dairy products, home-brewed beer and mead, have a particularly high acetaldehyde content. Because of its pleasant fragrance, acetaldehyde is used as flavouring in yoghurts, sweets, desserts, bakery products, soft drinks, fruit juices and alcoholic beverages. Several hundred thousand tons of acetaldehyde are manufactured each year for industrial use.

It has been recommended that the daily acetaldehyde intake for a person of average weight (70kg) should not exceed 0.4 milligrams. This means that the acetaldehyde content of a 100ml serving of any alcoholic beverage or food should not exceed 50µmol/l. The acetaldehyde content of some foods can be many thousands of times higher than this safety limit. The most dangerous products in this respect are alcoholic beverages (such as calvados, sherry and ciders), fermented products and some fruits and fruit-based products.

Read more about the risks posed by acetaldehyde at http://www.biohit.com/acetium