Reference point
Open a bottle of traditional first-press fish sauce.
Do this before you read on. An entry only works when you have just smelled the thing.
Salty, fishy, with a cheesy note and a deep sweetness lying far underneath. The three layers separate only when smelled diluted.
The fishy note comes from volatile amines, the cheesy note from short-chain fatty acids. Both groups are also found in aged European cheeses, so fish sauce and blue cheese are close chemical relatives although nobody puts them side by side.
It is also a reference you can smell for understanding the idea of animalic notes in perfumery — a family of animal smells many people know only by name.
How to smell it
Put a drop of first-press fish sauce on a smelling strip or white paper, wait a minute for it to thin, then smell. Don’t smell straight from the bottle. Diluted, the three layers separate and you catch the sweetness at the bottom — something smelling straight from the bottle never shows.
Why this one is hard
Because the first reaction is almost always to back away. The dilution technique above solves most of the problem, and it is also the standard technique in professional fragrance evaluation.
Don’t confuse with
This entry
Fish sauce
Fermented family
Shrimp paste is cloudier and heavier, with a much stronger ammonia note, because it is fermented from whole shrimp.
This entry
Fish sauce
Fermented family
Soybean paste is fermented from beans, so it has no fishiness; fish sauce is fermented from fish, so it has clear volatile amines.
Scientific note
The fishy note of fish sauce comes from trimethylamine, formed when bacteria reduce the trimethylamine oxide naturally present in sea-fish tissue. The cheesy note comes from short-chain fatty acids such as butyric acid. Both groups are also found in aged European cheeses — two distant cuisines arriving at the same point by two different microbial routes.
In Vietnamese life
Traditional fish sauce fermented for twelve months or more has a completely different profile from blended industrial fish sauce. The difference lies precisely in the deep sweetness — something that forms only with time and cannot be added by blending.