Dave Pollen was one of those teachers that you will always remember. I remember his pronunciation of the element Platinum, his irreverent humour and the Francis Rossi pony tail which on his receding late forties head made him look like his hair had slipped back 6 inches. Aldehydes always remind me of Dave because he once nearly blew himself up in front of the class trying to make one in a test tube. Dave was a good bloke who helped me get my chemistry A level at night school and even made the Born-Haber cycle interesting, although mainly because he confused himself while explaining it.
This week’s flavour compound is Acetaldehyde or systemically ethanal. Acetaldehyde as you may have noticed from the balloon dog is ethanol with one less hydrogen atom. An enzyme in the body (alcohol dehydrogenase) removes this hydrogen in order to facilitate the excretion of alcohol. High levels of acetaldehyde in the body correspond to the reported symptoms of a hangover but a direct link has not been established. The "hair of the dog" hangover cure is thought to work by affecting the activity of alcohol dehydrogenase. My advice for avoiding hangovers is don’t drink too much. Advice which I should have taken last weekend.
Acetaldehyde is produced during fermentation and smells like the bruised skin of a green apple (unripe Granny Smith). Some say the term green beer comes from the green apple-like aroma of beer at the end of fermentation due to acetaldehyde. I suspect that the use of the word green is meant to convey the fact that it is unripe or not ready for consumption.
Acetaldehyde is also produced by a few spoilage organisms which I won’t bore you with.