Magic molecules

Home Technologist 04 Smell Magic molecules

Hundreds of volatile compounds give new and old books their distinctive and bewitching smells.

Photo of rows of antique books on shelves

The fragrance of words

Depiction of the molecular structure of a vanillin molecule

Better known as ice cream flavouring, vanillin is usually extracted from plants but also spontaneously forms from paper cellulose over time.

 

Depiction of the molecular structure of a nonenal molecule

The oxidation of fatty acids produces 2-nonenal amongst many different aldehydes, a group of molecules used in the perfume industry.

 

Depiction of the molecular structure of a lignin moleculeLignin degrades into guaiacol, a molecule also present in wood smoke that contributes to the flavour of roasted foods such as coffee.

 

Depiction of the molecular structure of a camphor moleculeA penetrating odour similar to rosemary, camphor is produced by the decomposition of cellulose.

 

Depiction of the molecular structure of a furfural moleculeAn almond-like smell comes from furfural, also found in the vanilla plant and produced by the breakdown of cellulose.

 

 

A fresh sea breeze

Photo of an ocean cliff surrounded by sea water, waves and ocean spray

Before your eyes even see it, your nose senses that you’re approaching the sea. It’s a complex scent: iodine and brine, algae and seaweed, fish and birds. Five molecules help create the distinctive smell of the seashore. (Photo: istock.)

Depiction of the molecular structure of a trimethylamine (TMA) moleculeFish 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.

Depiction of the molecular structure of a dimethyl‑sulfide (DMS) moleculeMarine 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.

Depiction of the molecular structure of ectocarpene and dictyopterene A moleculesA 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.

 

Depiction of the molecular structure of a bromophenol moleculeThe characteristic taste of seafood comes from bromophenols. Through their diet, oysters, shrimp and crabs accumulate these molecules that exist only in marine environments.

 

Depiction of the molecular structure of a hydrogen sulfide moleculeThe 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

More on the science of smell: The sweet smell of sweat; Master of fragrances; Humans, dogs – and now e-noses

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