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Human nose
The dog's nose is one of the most sensitive olfactory organs (here: the nose of a Samoyed )

Fragrances or odorous substances include all natural and synthetic substances that develop an odor when perceived by the olfactory system. The smell is not a property of the substance, but is only given to it by the person who smells it. The term fragrance is often used synonymously, but is limited to fragrances that are formed by plants or animals and serve to communicate with them, for example as pheromones .

In order to be perceived as an odor, a substance must be volatile and dispersible in air . Highly volatile fragrances spread quickly and flood quickly, while those that are not volatile develop a lower vapor pressure ; When released into ventilated rooms, volatile ones tend to disappear. Whether a vaporized amount of substance can be smelled depends not only on its concentration in the air volume, but also on whether it is above the odor threshold . The odor thresholds can be very different for different fragrances and are each determined by the olfactory ability of the perceiver. The lower its odor threshold for a fragrance, the less concentrated it can be smelled; and the less this threshold increases during exposure, the longer this concentration can lead to an odor impression.

Most fragrances are molecules below a certain molecular size (or molecular mass , M R <300) and consist of a polar component, for example a functional group , and a non-polar component, such as a hydrocarbon skeleton . Specific properties of their molecular structure are detected through contact with different types of receptive transmembrane proteins in the mucous-covered cilia of various types of olfactory cells . Since the proteins of the olfactory receptors are chiral , the mirror-image enantiomers of an odorous substance (e.g. carvone ) can produce different smells. Functional groups that are apparently essential for triggering an odor are called osmophores .

Fragrances are basic substances in perfume production. In 2006, sales on the world market for all substances used as odorants or flavorings (fragrances and flavorings ) amounted to around 18 billion US dollars.


Examples of chemicals used as odorous substances:

For the breakdown of fragrances according to their carrier substance, see also the article Perfume .


Individual evidence

  1. Entry on fragrances. In: Römpp Online . Georg Thieme Verlag, accessed on July 25, 2013.