Anethole
Also written trans-anethole, anethol, trans anethole
Quick answer
The compound that makes aniseed, fennel and star anise smell alike despite belonging to three unrelated plant families — one of the clearest cases in cooking of chemistry cutting across botany.
What it does
Anethole is the sweet liquorice-like aroma common to aniseed, fennel seed and star anise, and it is genuinely sweet on the tongue as well as sweet-smelling — appreciably sweeter than sugar by weight, which is why anise-forward spices make a dish taste sweeter without any sugar being added. The three spices that carry it are not related to one another: aniseed and fennel are in the carrot family, star anise is a magnoliid tree, and liquorice, which tastes of the same thing, is a legume owing its sweetness to a completely different compound. The resemblance readers notice is real and is chemical, and the botany has nothing to do with it.
How it behaves when cooked
Four properties of the molecule, and what they mean at the stove.
- Volatility
- high
- Fat solubility
- high
- Water solubility
- low
- Heat stability
- moderate
Anethole is highly fat-soluble and barely water-soluble, and that single asymmetry produces the most visible piece of kitchen chemistry in the spice world: an anise spirit turns cloudy when water is added, because the anethole dissolved in alcohol comes out of solution as the alcohol is diluted. The same behaviour governs cooking. Anise spices bloom well in oil and give up very little to a watery poaching liquid, so a fennel-seed sausage or a star-anise braise with fat in it tastes of anise throughout while the same spice in a lean court-bouillon stays in the pod. It is volatile enough to be lost from an open pot over a long cook, which is why star anise is added to a braise whole and often removed and replaced. Toasting develops it pleasantly up to a point and then destroys it quickly — the window on fennel seed is famously short.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
- AniseedPrincipal component
- Fennel seedPrincipal component
- Star anisePrincipal component
The reason star anise substitutes for aniseed at all. It is not a related plant and the substitution works purely because both are anethole-dominant.
- Hoja santaContributing component
- Liquorice rootContributing component
Genuinely present in the root, and not the source of its sweetness — that is glycyrrhizin. The two compounds together are why liquorice reads as both sweet and anise-like when only one of them is doing each job.
- TarragonContributing component
Present in smaller quantity than estragole and reinforcing the same impression, which is why tarragon reads as a relative of aniseed and fennel despite being an Artemisia rather than an Apiaceae.
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Estragole
An isomer — the same atoms rearranged — found alongside anethole in the same spices. It smells related but greener and more basil-like, and unlike anethole it is the compound regulators have assessed. Sharing a formula is exactly why the two are so often conflated.
Glycyrrhizin
Liquorice tastes of anise and contains no anethole; its sweetness comes from an unrelated saponin. Anise-flavoured confectionery sold as liquorice often contains anethole and no liquorice root at all.
Questions this page answers
- what is anethole
- what does anethole do
- which spices contain anethole
- what is trans-anethole
- what is anethol