Guaiacol
Also written 2-methoxyphenol, guaiacol (smoke phenol)
Quick answer
The phenol that smells of smoke — produced when the lignin in wood breaks down under heat, and the reason a fire-dried spice tastes of the fire rather than of itself.
What it does
Guaiacol is smoky, medicinal and faintly sweet, with something of creosote and of a smoked ham about it. It is detectable at very low concentrations, which is why a few days over a smouldering fire changes a spice permanently and why a smoked spice stored beside an unsmoked one will taint it. It is not a flavour any of these plants produces: every molecule of it in a spice came out of burning wood.
How it behaves when cooked
Four properties of the molecule, and what they mean at the stove.
- Volatility
- moderate
- Fat solubility
- high
- Water solubility
- low
- Heat stability
- high
Smoke compounds are unusually persistent, and that single property governs how every smoked spice in this catalogue behaves. They survive long cooking essentially intact while the fruit and floral notes around them disappear, so a smoked spice grows relatively more smoky as a dish reduces — which is why smoked paprika is used with a lighter hand in a four-hour stew than the colour tempts you to, and why an old tin of pimentón smells strongly of smoke and of nothing else. Being fat-soluble, they extract readily into oil and carry through a whole dish from a small quantity. And because they are volatile enough to migrate, a jar of chipotle or smoked paprika left open in a spice drawer will make its neighbours smell smoky within weeks, which is the one genuine case in this dataset for storing a spice away from the others.
Not present until the plant is damaged
Lignin (guaiacyl units)
Not present in the plant at all. Guaiacol is produced when the guaiacyl portion of lignin in wood pyrolyses at smouldering temperatures, and it lands on the food from the smoke. Softwoods are richer in guaiacyl lignin than hardwoods, which is part of why different woods give different smoke — and why the oak specified for pimentón de la Vera is a specification rather than a habit.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
- ChipotlePrincipal component
A ripe jalapeño smoke-dried until leathery. The smoke is why chipotle is not simply a hot dried chilli.
- Smoked paprikaPrincipal component
Acquired over about a fortnight of slow oak-smoke drying, and the entire difference between this and ordinary paprika.
- Black cardamomContributing component
The Himalayan pod is dried over wood fire in Sikkim and Nepal, by the same mechanism and with a different wood.
- TsaokoContributing component
From fire-drying in Yunnan, sitting over a camphorous base — which is why a pho broth reads as smoky without anything smoked being in it.
- PaprikaPresent in small amounts
Only in the smoked grades. Hungarian and Murcian paprika are dried without fire and carry none.
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Syringol
The other half of wood smoke, from a different part of the lignin. Guaiacol leans medicinal and creosote-like; syringol is closer to what most people mean by "smoked food". Hardwoods give proportionally more syringol, softwoods more guaiacol, which is the chemical basis of the wood mattering.
Liquid smoke
Condensed wood smoke, and largely these same compounds — which is why it works at all. The difference a taster notices is that it arrives sharp and sits on top, where a fortnight in a drying house puts the smoke through the flesh.
Questions this page answers
- what is guaiacol
- what does guaiacol do
- which spices contain guaiacol