Dimethyl sulfide
The nori and seaside note of good Japanese green tea — and the compound umami is routinely mistaken for.
What a drinker notices
- Aroma — an aroma
Nori, seaweed, sea air, and at higher levels cooked vegetable or canned corn. It arrives through the nose, which is what separates it from the savoury weight on the tongue that so often accompanies it.
How much of it there is matters: Marine and appealing in a narrow band; above it the character turns towards cooked cabbage and is a fault. Over-steaming is the usual route across the line.
What this gets credited for, wrongly
This is the single most-merged pair in Japanese tea description. Umami is the free amino acids led by theanine, tasted on the tongue; the nori note is this compound, smelled. Both rise with shading, so a shaded tea has both, and almost every account credits one for the other.
What it is
The marine, seaweed, low-tide quality of a fine gyokuro or a deep-steamed sencha is not umami and is not theanine. It is largely this compound, formed when heat breaks down a sulfur-bearing amino acid the leaf carries, and it is an AROMA where umami is a TASTE. The two travel together because both track shading — cover the plant and you raise the amino acids and the sulfur precursor at once — and that shared cause is exactly why they get merged into one claim. Separating them is the difference between describing a tea and explaining it.
Chemically: Volatile organosulfur compound, formed from a sulfur-bearing amino acid on heating.
Where it occurs in the plant
Not present as such in the growing leaf. Its precursor accumulates in the leaf, more so under shade, and heat during steaming and firing releases the volatile compound.
What processing does to it
In tea, processing is not a modifier applied to a fixed composition — it is what decides the composition. These are the steps that move this compound, and each links to the step itself.
- Shading — Raises it
- Raises the precursor along with the amino acids, which is why deeply shaded teas carry the marine note most strongly and why the two qualities appear inseparable to a drinker.
- Steaming (Japanese fixation) — Creates it
- Heat converts the precursor into the volatile compound. Steaming is where the note is created, which is why it is characteristic of Japanese tea and largely absent from pan-fired Chinese green tea made from comparable leaf.
- Final firing (hiire) — Raises it
- The final firing produces more of it, and over-firing pushes the character from nori towards cooked vegetable. It is one of the things a Japanese refiner is balancing.
How brewing brings it out
Extraction rate: Fast — among the first things out of the leaf
Extremely volatile — the most volatile compound in this catalogue. It is out of the cup within moments of pouring, so a gyokuro assessed five minutes after brewing has lost the note that most distinguishes it.
Across infusions: Overwhelmingly a first-infusion phenomenon, and even then only briefly.
Water: Extremely volatile and lost to heat and standing rather than to water chemistry. A shaded green brewed cool in a covered vessel keeps the marine note; the same leaf brewed at boiling in an open pot has driven much of it off before the cup reaches a table.
What you can change
- Smell the cup immediately after pouring
- Brew into a small cup and drink at once
- Avoid re-heating — the note does not survive it
Where this gets misdescribed
That a shaded Japanese tea tastes of the sea. It smells of the sea and tastes savoury, and those are two compounds working through two senses. Anyone who has held their nose while drinking one has run the experiment.
Teas this compound defines
Read next
- L-theanine — The savoury amino acid that makes shaded green tea taste like broth, and the compound that explains why shading exists at all.
- Free amino acids — The savoury half of the balance that decides whether a green tea tastes sweet or brisk — and half of the ratio Chinese graders actually use.
- Green-leaf volatiles — The smell of cut grass, made within seconds of the leaf being damaged, and the aroma most of tea processing exists to get rid of.
What this page does not say
This record describes an aroma compound, how processing makes it and how quickly it leaves a cup. It makes no statement about what it does in a body.
Sources
- TeaHQ editorial synthesis — TeaHQ
This page is TeaHQ’s own synthesis of well-established tea chemistry. No external technical document stands behind it, and that constraint is why there are almost no numbers here: directions, rankings and mechanisms are stated plainly, quantities are not, because a figure nobody can check would look more authoritative than it deserves.