Compound library · Biosynthetic pathways
Heat (Maillard reaction and pyrolysis)
Fire breaks large molecules into ones you can smell
12 compounds in the library
12 compounds follow this pathway
The last group is not made by any living thing. These compounds form when heat breaks down large molecules that have no smell of their own: starch, sugars, proteins, cellulose, lignin.
The Maillard reaction between sugars and amino acids gives the pyrazines of roasted coffee and bread. Caramelisation gives furanones and maltol. Pyrolysis of wood gives the guaiacol and syringol of smoke.
This is the only pathway humans control directly. Turn the flame up or down and you change the product, and the whole craft of cooking rests on that understanding.
Compounds that follow this pathway
| Compound | Chemical family | Boiling point | Threshold |
|---|---|---|---|
| 2,5-Dimethylpyrazine | Other compounds | 155 °C | — |
| 2-Furfurylthiol | Other compounds | 155 °C | 0.010 ppb |
| Furfural | Aldehydes | 162 °C | 3.0 ppm |
| 2-Acetyl-1-pyrroline | Other compounds | 181 °C | 0.100 ppb |
| Phenol | Phenols | 182 °C | 5.9 ppm |
| 5-Methylfurfural | Aldehydes | 187 °C | — |
| Furaneol | Other compounds | 188 °C | 0.030 ppb |
| Maltol | Other compounds | 200 °C | 9.0 ppm |
| Guaiacol | Phenols | 205 °C | 3 ppb |
| Naphthalene | Other compounds | 218 °C | 21 ppb |
| Creosol | Phenols | 221 °C | 20 ppb |
| Syringol | Phenols | 261 °C | — |
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.