4 min read ·
Theanine is the amino acid behind everything people like about shaded tea. It is what makes a good cup taste sweet and savoury rather than merely green, and kabusecha has more of it than most, because covering the plant before harvest is precisely what builds it.
So the obvious question is how to get more of it into the cup. The answer turns out to be the opposite of what almost every brewing guide says.
The thing most brewing guides get wrong
You will read everywhere that cool water extracts more theanine. It doesn't.
Theanine is highly water-soluble and comes out of the leaf at roughly the same rate whether the water is tepid or near-boiling. Temperature barely moves it. What temperature moves dramatically is everything else.
Catechins — the compounds responsible for astringency and bitterness — extract far more readily in hot water. So does caffeine. Push the temperature up and you pull out a great deal more of both, while the theanine stays more or less where it was.
You cannot brew for more sweetness. You can only brew for less of what hides it.
This is why a cool brew tastes sweeter and rounder. Not because there is more theanine in the cup, but because there is less bitterness sitting on top of it. The ratio shifts, and what was always there becomes audible.
Why kabusecha rewards this more than most tea
Shading is the reason. Covered before harvest, the plant holds on to amino acids including theanine, and produces fewer of the compounds that turn sharp. Kabusecha arrives in your hands already weighted towards sweetness.
Brew it like an ordinary green tea — boiling water, straight in — and you undo that work in ninety seconds. All the catechin extraction you avoided in the field comes flooding back in the pot.
Brew it gently and the shading does what it was meant to do.
How we brew it
Hot
8–10g of leaf (about two heaped teaspoons) · 200ml of water at 60–70°C · 90–120 seconds
The generous leaf ratio is deliberate. Because you are brewing cool, extraction is slower across the board, and more leaf compensates without reaching for heat. The result is concentrated and soft rather than thin.
To reach temperature without a thermometer, boil the kettle and let it stand for four or five minutes, or pour the water between two cups a couple of times. Each transfer sheds roughly ten degrees.
Cold
12g of leaf per 500ml · 6–8 hours in the fridge
This is the furthest you can push the ratio. At refrigerator temperature, catechin and caffeine extraction drops away almost entirely while the theanine comes out over the long steep regardless. The cup is noticeably sweeter than anything you can achieve hot, and markedly lower in caffeine.
It is worth doing once simply to taste the difference. Nothing demonstrates the principle more plainly.
Either way, strain gently
Avoid stirring or agitating the leaves. Physical disturbance breaks leaf matter and pushes fine particles and bitterness into the liquor. Pour slowly and let it find its own way out.
What each variable actually does
| Change this | And this happens |
|---|---|
| Lower the temperature | Less bitterness and caffeine; theanine largely unchanged |
| Raise the temperature | Sharper, more astringent, more caffeine |
| More leaf | More of everything; strength without heat |
| Longer steep, cool water | Builds body while bitterness stays low |
| Longer steep, hot water | Bitterness climbs quickly |
| Agitating the leaves | Fine particles and harshness in the cup |
The principle underneath all of it: heat is the variable that costs you something. Leaf quantity and time are the ones that don't.
The second steep
Don't discard the leaves after one pour. Kabusecha gives a good second infusion, and because much of the theanine has already gone into the first cup, the second wants different handling: slightly hotter water, and a much shorter time — thirty seconds or so.
It will taste brighter and less round than the first. That is not a failure, it is a different register of the same tea, and worth tasting alongside the first cup rather than instead of it.
Common questions
Does cold water extract more theanine?
No, though it is widely repeated. Theanine extracts at broadly the same rate across temperatures. What changes is catechins and caffeine, which come out far more readily in hot water. Cooler brewing shifts the balance towards theanine rather than increasing it, which is why the cup tastes sweeter.
What temperature should I brew kabusecha at?
Around 60–70°C for a hot brew, with 8–10g of leaf per 200ml and a steep of 90–120 seconds. Boil the kettle and let it stand four or five minutes, or pour between two cups a couple of times, each transfer losing roughly ten degrees.
Why does kabusecha have more theanine than sencha?
Shading. Covering the plants before harvest means the leaf retains more amino acids, theanine among them, and develops fewer of the compounds that turn sharp. Sencha is grown in full sun, so it arrives with a different balance.
Is cold brew lower in caffeine?
Yes. Caffeine behaves like the catechins and extracts far less at low temperatures, so a cold brew is both sweeter and gentler on caffeine than the same leaf brewed hot.
Can I re-steep kabusecha?
Yes, and it is worth doing. Use slightly hotter water and a much shorter steep, around thirty seconds. The second cup is brighter and less rounded than the first, since much of the theanine has already gone.