Compound library · Biosynthetic pathways
Microbial origin
Made by bacteria and yeasts, not by plants
11 compounds in the library
11 compounds follow this pathway Left of the dashed line are compounds lighter than any essential-oil component — they are gone before the main axis begins.
Many of the most important smells are made not by plants but by microorganisms. The geosmin of first rain is secreted by bacteria in the soil. Fish sauce, fermented shrimp paste, fermented bean curd, pickled greens and fermented sticky rice are all products of fermentation.
This pathway differs from the three above in one respect: it needs time and it needs conditions. Temperature, humidity, salinity and which microbial species dominates — all of them change the result.
That is also why fermented foods are harder to standardise than distilled essential oils, and why each region has its own flavour.
Compounds that follow this pathway
| Compound | Chemical family | Boiling point | Threshold |
|---|---|---|---|
| Trimethylamine | Other compounds | 3 °C | 0.500 ppb |
| Ethanol | Alcohols | 78 °C | 100.0 ppm |
| Diacetyl | Ketones | 88 °C | 10 ppb |
| Acetic acid | Other compounds | 118 °C | 20.0 ppm |
| Ethyl butanoate | Esters | 121 °C | 1 ppb |
| Isoamyl acetate | Esters | 142 °C | 2 ppb |
| Butyric acid | Other compounds | 164 °C | — |
| Ethyl hexanoate | Esters | 168 °C | 5 ppb |
| 2-Methylisoborneol | Alcohols | 207 °C | 0.015 ppb |
| 2,4,6-Trichloroanisole | Other compounds | 241 °C | 0.030 ppt |
| Geosmin | Alcohols | 270 °C | 0.004 ppb |
Three axes, three questions
This library classifies compounds along three axes, and each answers a different question.
Boiling point tells you when you smell a compound — early or late on the smelling strip. Chemical family tells you how it behaves — stable or fragile, and how to recognise it on an analysis. Biosynthetic pathway tells you where it comes from.
The third axis is the explanatory one. The other two describe how compounds cluster into groups; this one says why they cluster that way.