Reference point
A fresh straw mushroom snapped in two.
Do this before you read on. An entry only works when you have just smelled the thing.
Damp, slightly fishy, with a light metallic note. It is light and thin and does not spread far.
An eight-carbon alcohol dominates the whole thing, and the same compound appears in old cooking oil, in mouldy grain, in badly stored cereals. So recognising this smell is not just a matter of learning a word — it is a test you can use when you take delivery of a batch of raw material.
Fresh and older mushrooms give two intensities of the same smell. The longer they are kept, the stronger it gets, and at some point it turns from a sign of freshness into a sign of spoilage.
How to smell it
Snap a fresh straw mushroom in two and smell the break immediately. Then leave the other half out for two hours and smell again. The same smell at two intensities, and you will understand why it is both an appetising smell and a warning one.
Why this one is hard
Because it sits on the border between pleasant and unpleasant, and that border differs from person to person. Don’t try to decide which side it belongs to; just note the intensity.
Don’t confuse with
This entry
Straw mushroom
Earthy family
First rain has a cold mineral note; straw mushroom is fishier, with a metallic note.
This entry
Straw mushroom
Earthy family
Leaf litter is fungus and earth added together in concentrated form; straw mushroom is thinner, fishier and has a clear metallic note.
This entry
Straw mushroom
Earthy family
Dried mushrooms have sulphur compounds formed during drying, giving a richness fresh mushrooms entirely lack.
Scientific note
1-Octen-3-ol is called mushroom alcohol and forms when the mushroom’s enzymes break down fatty acids. The same compound appears when cooking oil starts to go rancid and when grain goes mouldy. The human nose is unusually sensitive to it, perhaps because it is an early sign of spoiled food.
In Vietnamese life
Straw mushrooms are grown on rice straw after the harvest all over the Mekong Delta. For many people in the south the smell of straw mushrooms goes with the flood season and with piles of composting straw behind the house.