Tea chemistry

Tea's principal alkaloid, bitter at concentration, and the compound most often blamed for a drying sensation it does not cause.

The minor methylxanthine, present in every tea and dominant in none — the reason a tea leaf is not a one-alkaloid plant.

The third methylxanthine, present in tea in trace amounts, and named after the plant despite being far more abundant elsewhere.

The second most abundant free amino acid in a heavily shaded tea, and the one that reveals how much nitrogen the field was given.

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.

The compound an entire tea category is named and sold on, and the one thing in that category a drinker cannot taste.

The compound umami was defined from, present in tea in free form and responsible for the part of a savoury cup that tastes like stock rather than like tea.

The savoury amino acid that makes shaded green tea taste like broth, and the compound that explains why shading exists at all.

The largest soluble fraction of a green tea leaf, the source of astringency, and the compounds oxidation turns into everything a black tea is.

The other galloylated catechin, and weight for weight the most drying thing in the leaf.

The catechin without a gallate group — bitter more than drying, and the partner EGCG needs to make a theaflavin.

The most abundant catechin in green tea, and the clearest single demonstration that astringency and bitterness are different things.

The smallest and mildest tea catechin, present in cocoa and apples as well, and the other half of a simple theaflavin.

What roasting actually does to a tea's catechins: not destroys them, flips them. The same molecules, mirrored at one carbon, sitting differently on the tongue.

A small family of catechin variants that a handful of Japanese cultivars carry unusually — and the clearest case on this site of a compound famous for a reason TeaHQ will not discuss.

The cloud that forms in a black tea as it cools. Not a fault, not hard water, and the single most misdiagnosed thing that happens in a glass of iced tea.

The dark, water-soluble polymers of ripe pu-erh and other dark teas — why a shou is almost black and almost never drying.

The bright orange-red pigments oxidation builds from catechins, and the compounds the tea trade means by briskness.

The largest fraction of a black tea liquor, responsible for its depth and body, and not actually a compound at all.

The dimers formed when two catechins of the same type couple — the oxidation route oolong takes and black tea largely does not.

Present in small amounts, detectable at very low ones, and a large contributor to the velvety, mouth-coating dryness catechins alone do not explain.

The gallate group after it has been separated from its catechin — small, sour, drying, and a marker of how far a dark tea has fermented.

A minor acid that contributes to mouthfulness — the sense that a liquor has substance rather than merely strength.

Stewed fruit, rose and honey at a level almost nothing else in tea can match, and the compound most often handed sole credit for muscatel.

Violet and dried-fruit aroma from broken-down carotenoid pigment, detectable at some of the lowest levels in tea.

A principal source of rose character in tea, and half of the clearest compositional difference between China-type and Assam-type plants.

A major floral aroma compound of tea, largely stored bound to sugar in the leaf and set free by processing.

What linalool becomes when the leaf is oxidised — sweeter, creamier and less sharply floral, and a marker of how far a tea has gone.

A woody-floral aroma compound that rises when the leaf is stressed — by bruising, and famously by insects.

Leaf alcohol: the specific compound behind the smell of freshly cut grass, and the one a tea maker is judging when they smell a withering trough.

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.

A creamy, peach-and-jasmine note that arrives in tea both from scenting with real flowers and from the leaf's own chemistry.

The wintergreen and minty-medicinal note of some Darjeelings and oolongs — a plant stress signal that ends up in the cup.

Rose and honey, built from an amino acid. Filed with the terpenoid florals everywhere in tea writing, and moved by an entirely different set of steps.

Jasmine at trace level and something much worse above it — the clearest demonstration in tea that dose decides identity.

The roasted, nutty and toasted aromas — compounds that do not exist in a tea leaf until heat makes them.

Malt. The group made when firing spends the leaf's own amino acids against its own sugars, and the reason the maltiest teas are the ones with the most amino acid to spend.

The nori and seaside note of good Japanese green tea — and the compound umami is routinely mistaken for.

The smell of smoke, deposited on the leaf from burning pinewood — the compound that makes Lapsang Souchong what it is.

The purple of purple tea — water-soluble, unlike the other pigments here, and it changes colour with the acidity of the water.

The yellow-orange pigments hidden under the green — and the raw material for a good part of tea's fruit and floral aroma.

The green of the leaf, and — because it barely dissolves — the reason a steeped green tea is yellow while a whisked one is green.

The brown that heat makes. Why a roasted tea pours darker than the green tea it was, and why that darkness has nothing to do with oxidation.

What chlorophyll becomes when heat or acid knocks the magnesium out — and the whole explanation for green tea going olive.

The cell-wall polysaccharides behind thickness and slipperiness — the quality Chinese tasters call hou and English-language tasting notes struggle to name.

Present in small amounts, tasted only faintly, and indispensable as the fuel for every roasted aroma in tea.

The fraction a drinker never tastes and cannot do without: the raw material every green-leaf aroma is cut from, and the part of the leaf that goes off.

The sourness axis, and the reason a tea liquor is mildly acidic — which decides what colour it is as much as what it tastes like.

The surface-active compounds that make matcha foam and a poured cup froth — and a small, throat-catching bitterness alongside.

The tea plant is one of the few crops that accumulates aluminium, and most of what it accumulates never reaches the cup.

A soil ion the tea plant accumulates steadily with leaf age — which is why the coarsest teas carry the most and buds carry the least.

One of the elements tea is genuinely notable for accumulating, and — like the others — invisible in the cup.