Arginine
The second most abundant free amino acid in a heavily shaded tea, and the one that reveals how much nitrogen the field was given.
What a drinker notices
- Sweetness — a taste
A soft sweetness that sits underneath the savoury weight rather than beside it. On its own it is not a taste anyone identifies; in a shaded tea it is part of why the sweetness reads as thick instead of thin.
What it is
Arginine is the tea plant's nitrogen store: it is the form the plant parks surplus nitrogen in, and its level in the shoot rises sharply with fertilisation and with shading. That makes it the most agronomic compound on this list — a high arginine share is a fact about how a field was managed rather than about a cultivar or a region. It contributes to sweetness in the cup, and it is an eager participant in the browning reactions of firing, so a heavily fertilised leaf browns and develops toasted aroma faster than a lean one at the same roast.
Chemically: Protein amino acid, present in free form; the leaf's principal nitrogen store.
Where it occurs in the plant
Accumulates in root and stem as a nitrogen reserve and moves into the shoot with new growth. Highest in intensively fertilised, shaded Japanese production and low in extensively grown leaf.
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
- Rises steeply under cover, more steeply than most of the pool, so a deeply shaded tencha carries a great deal of it.
- Final firing (hiire) — Turns it into something else
- A ready participant in the browning reactions of the final firing. A leaf rich in it develops toasted and nutty aroma at a lower firing temperature than a leaf that is not.
How brewing brings it out
Extraction rate: Fast — among the first things out of the leaf
Soluble and early, on the same schedule as the rest of the free amino acids. No brewing decision isolates it.
Across infusions: Front-loaded with the rest of the amino acids, so the savoury weight of a session is an opening characteristic rather than a sustained one.
Water: Shares the soft-water preference of the amino acid group, for the same reason: what it contributes is a low-intensity savoury weight, and low-intensity tastes are the first casualty of mineral-heavy water.
Leaf, ratio and agitation: Follows the same heavy-leaf, small-volume, short-contact logic that favours theanine, because the amino acids extract as a group.
What you can change
- Moves with the amino acid pool — brew cool and short
- Not separable from theanine by any brewing change
Where this gets misdescribed
That the savoury sweetness of a shaded tea is a varietal quality. A large part of it is nitrogen management, and the same cultivar grown lean tastes noticeably different.
Teas this compound defines
Read next
- 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.
- L-theanine — The savoury amino acid that makes shaded green tea taste like broth, and the compound that explains why shading exists at all.
- Pyrazines — The roasted, nutty and toasted aromas — compounds that do not exist in a tea leaf until heat makes them.
What this page does not say
This record describes an amino acid in the leaf, what farming does to its level and what it contributes to taste. Nothing here concerns nutrition or 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.