Why does my matcha taste fishy?
Updated By Mio.KShare
Search this and you will find hundreds of people asking it and almost nobody answering it. The threads are on Reddit and under Facebook posts and in TikTok comments, and they split into two camps that talk past each other: one says the tea has gone off, the other says you bought a cheap one. Almost no one writes it down properly.
Both camps are right, because there are two different faults and one thing that is not a fault at all. Good matcha does taste savory — of nori, of broth, of something green and marine — and if you have only met tea as a bright drink, that can read as fish the first time. That is umami, and it is what you paid for. Actual fishiness is different: it is oily, a little sour, and it lingers unpleasantly. That comes from a tea that has oxidized, or from one milled from later, stemmier leaf. The first two minutes with the open tin will tell you which you have.
Seaweed is not fish, and the difference is the whole answer
Matcha is shaded for three to four weeks before picking, which keeps the leaf making the amino acid that tastes savory instead of turning it into the compounds that taste bitter. Savory is the point of the shading. A good bowl of thin tea should taste sweet, grassy and broth-like at once, and a lot of first-time drinkers do not have a word for that except "seaweed."
| Umami (what it should be) | Fishy (a fault) | |
|---|---|---|
| Where you notice it | Mid-palate, with the sweetness | In the nose first, before you drink |
| What it resembles | Nori, dashi, fresh peas, broth | Fish oil, old nuts, a damp cupboard |
| Texture of the taste | Round, and it fades cleanly | Oily, with a sour edge that stays |
| The color of the powder | Vivid, almost fluorescent green | Dulled, yellowish or olive-brown |
| What to do | Nothing. This is the tea | Read on |
If the powder is still brilliantly green and the smell out of the tin is sweet, you are tasting umami and there is nothing wrong. Give it a week. Almost everyone who stays with matcha stops reading that note as fish and starts looking for it.
Fault one: the tea has oxidized
This is the commonest real cause, and it is the one people find hardest to believe because the tin looks fine.
Matcha is not leaf. It is leaf ground to a powder a few microns across, which means an enormous amount of surface meeting the air at once. The things that make it fishy — the oxidation of its fats and amino acids — happen to that whole surface at the same time, not slowly from the outside in. A sealed tin of sencha is forgiving. A half-used tin of matcha in a warm kitchen is not.
Four things do the damage, in roughly this order of speed: heat, light, air and moisture. Kept properly, a sealed tin holds for six to twelve months; once opened and kept cool and closed, four to eight weeks is the honest working figure. Left open on a counter by a window, it can be noticeably worse in a fortnight.
The test is the smell, not the taste, and you do it before you whisk anything. Open the tin and put your nose to it. Fresh matcha smells sweet and green, a little like fresh-cut grass with something creamy behind it. Oxidized matcha smells flat, then faintly of oil, then of old nuts. You will know inside two seconds, and you will not have wasted a bowl finding out.
Fault two: it was never very good
The second cause has nothing to do with how you kept it.
Tea picked later in the year, from leaf lower on the plant, with more stem and vein left in, and ground quickly on steel rather than slowly on stone, tastes coarser in every direction — more bitter, more astringent, and more likely to carry that oily marine note. None of this is visible through a tin, and none of it is fixed by the words on the front. The grade names are not regulated, so they cannot tell you which you have. Harvest date, origin and milling date can.
There is a plain tell at the bottom of the price range: cheap green powder is often not matcha at all. Ground sencha, or matcha cut with it, is common, legal, and photographs identically. It is also much more prone to tasting fishy, because it is made of exactly the leaf matcha leaves out. How to tell them apart is a separate piece.
Why the cafe version is often the worst of it
People ask this about chain-cafe matcha more than about anything they make at home, and the answer is not mysterious.
A cafe pouring hundreds of drinks a day is not using thin-tea grade, and usually is not using plain matcha at all — most of the big chains work from a sweetened blend in which sugar is the first ingredient. That powder is chosen to survive milk and ice, not to be drunk on its own. Combine a coarser tea with an enormous open container behind the counter and a lot of heat, and the marine note arrives reliably. If the only matcha you have met came through a straw, you have not yet met the thing people are describing.
So: which one do you have
| What you observe | Most likely cause | What to do |
|---|---|---|
| Brilliant green, smells sweet, tastes savory | Nothing is wrong. This is umami | Drink it. Thin it a little with more water |
| Dull or yellowish, smells flat or oily | Oxidized | Use it for baking or lattes. Buy smaller tins |
| Green enough, but harsh and fishy from the first day | Later-harvest or stemmy tea | Not your fault and not fixable. Change tea |
| Fishy and gritty on the tongue | Ground sencha rather than matcha | Change supplier |
| Fine at home, fishy only from cafes | A sweetened blend, not plain matcha | Nothing to fix. They are different products |
| Tastes bitter rather than fishy | A different problem | Bitter has its own three causes |
Can you rescue it
Not back into a bowl of thin tea. Nothing you do to oxidized matcha reverses the oxidation, and thin tea is the one preparation with nowhere to hide — no milk, no sugar, no ice. Whisking it better will not help, and whisking it cooler only mutes it.
It is still perfectly good in anything with milk or sugar in it: a latte, baking, ice cream. That is not a consolation prize, it is what the coarser grades are for. The only thing I would not do is keep drinking it plain and conclude that this is what matcha tastes like.
And buy the smaller tin next time. Thirty grams is about fifteen bowls, which is a fortnight for most people and lands almost exactly on the window where matcha is still worth drinking plain. The tea I stock comes in that size for the same reason.
Questions I get asked
Is it normal for matcha to taste like fish?
A clean savory note — nori, broth, something marine — is normal and is the shading doing its job. Actual fishiness, the oily kind you smell before you drink and taste afterward, is not. The powder tells you which: vivid green and sweet-smelling means umami, dull and oily-smelling means oxidation.
How do I tell if my matcha has gone bad?
Open the tin and smell it. Fresh is sweet and grassy; stale is flat, then oily, then like old nuts. Color confirms it — the brilliant green fades toward yellow or olive. It will not make you ill, it will simply stop being worth drinking on its own.
Why does the matcha from a chain cafe taste like fish?
Because it is usually a sweetened blend rather than plain matcha, built from coarser tea to stand up to milk and ice, and held open in quantity. It is a different product from a tin you whisk at home, and it is not a fair sample of what matcha tastes like.
Does whisking it differently help?
No. Whisking changes texture and how the first mouthful lands; it does not change what is in the powder. If the tea is oxidized or coarse, the best-made bowl in the world is still that tea.
Should I refrigerate matcha to stop this?
Only if it is unopened and you let it come fully to room temperature before opening, which most people forget. Taking a cold tin into a warm kitchen condenses water onto the powder, and moisture is one of the four things you are trying to keep away from it. A cool, dark cupboard and a smaller tin beat a fridge for almost everyone.
Where this fits
For what a good bowl should taste like in the first place, see what does matcha taste like. Taste problems usually come down to storage or grade. How to store matcha covers the first and what the grade words actually mean covers the second. If the trouble is bitterness rather than this, that has its own causes. And if you are starting out, the beginner's guide covers the tools; the complete set puts them together with the tea.
And if the problem is the opposite — that it tastes of almost nothing at all — that is usually the milk.
Written by Mio.K, who chooses everything in this shop by hand in Japan.