Hundreds of volatile compounds give new and old books their distinctive and bewitching smells.
The fragrance of words
Better known as ice cream flavouring, vanillin is usually extracted from plants but also spontaneously forms from paper cellulose over time.
The oxidation of fatty acids produces 2-nonenal amongst many different aldehydes, a group of molecules used in the perfume industry.
Lignin degrades into guaiacol, a molecule also present in wood smoke that contributes to the flavour of roasted foods such as coffee.
A penetrating odour similar to rosemary, camphor is produced by the decomposition of cellulose.
An almond-like smell comes from furfural, also found in the vanilla plant and produced by the breakdown of cellulose.
A fresh sea breeze
Fish get their unmistakable odour from trimethylamine (TMA). The lemon juice you squirt on the catch of the day when it’s on your plate transforms TMA into a non-volatile molecule and keeps it further from your nose.
Marine bacteria that feed on phytoplankton produce dimethyl‑sulfide (DMS), a strong scent also present in truffles, cheese and flatulence. When evaporating from the oceans, DMS attracts albatrosses to the krill. It also acts as a seed for water droplets, catalyzing the formation of clouds.
A typical marine smell after the tide has ebbed comes from ectocarpene and dictyopterene A, two sex hormones produced by seaweed eggs to attract the sperm.
The characteristic taste of seafood comes from bromophenols. Through their diet, oysters, shrimp and crabs accumulate these molecules that exist only in marine environments.
The smell of rotten eggs comes from hydrogen sulfide, a simple volatile molecule produced by microbes feeding on organic matter, such as seaweed decomposing on the shore.
By Luc Henry