Let me begin with a fact that until recently I did not know myself: white, green, yellow, oolong, black and pu-erh are all one and the same botanical species. Camellia sinensis, a relative of the garden camellia. There are no “black bushes” and “green bushes” in nature. The difference between types is created not by the plant but by what a human being does with the plucked leaf in the first twenty-four hours after harvest.

Part oneChemistry

Within the species there are two principal varieties.

Camellia sinensis var. sinensis – Chinese, small-leaved, mountain-grown, frost-hardy. The leaf accumulates more free amino acids, theanine above all. Hence the softness, the sweetness, the “brothiness” of good green teas.

Camellia sinensis var. assamica – Assam, large-leaved, tropical. More catechins, more caffeine, more powerful and coarser in flavour. It is the source of the classic Indian black teas and of almost all pu-erhs.

So the raw material already sets the corridor of possibilities. It is hard to make a delicate green tea from assamica, or a thick astringent breakfast blend from the small-leaved Chinese variety.

Incidentally, the tea plant’s genome was sequenced relatively recently, and it turned out to be enormous, around 3 billion base pairs. What is more, the genes responsible for catechin synthesis have been multiplied and duplicated far more generously in tea than in related camellias. The plant literally evolved in the direction of polyphenol production.

Six types of tea are six degrees of oxidation

The key enzyme here is polyphenol oxidase. While the leaf is intact, the enzyme and the catechins are stored in different compartments of the cell. The moment the leaf is bruised, rolled, broken, they meet, and enzymatic oxidation begins. Everything after that depends on the moment at which the producer presses pause.

Green tea. The enzyme is killed immediately, within the first hours. In China by pan-firing, in Japan by steaming. The difference is tangible: steam preserves more chlorophyll and catechins and gives a green, marine, seaweed profile (sencha, gyokuro). Pan-firing gives a nutty, chestnut character (Longjing). The catechins remain almost untouched, up to 30 per cent of the dry weight of the leaf.

White tea. Minimal intervention: withering and drying. A paradox: white tea is not “the weakest”. It is made from buds and the first small leaves, and the bud is the most caffeinated part of the plant. Silver Needles are perfectly capable of delivering more caffeine than an average black tea.

Yellow tea. The rarest and the most underrated type. After pan-firing, the leaf is stacked while still damp under cloth or paper for several hours or days. The process is called men huang, “sealing yellow”. The oxidation here is thermal and non-enzymatic: chlorophyll breaks down, catechins soften, sweetness appears without a single note of bitterness. The labour involved makes this type very rare.

Oolong. Partial oxidation, from 15 to 80 per cent, plus a trick of its own: the leaf is shaken repeatedly so as to damage precisely the edges. Inside, the leaf stays green; at the edges it oxidises. This is the moment when the explosive aromatics are born: linalool, jasmine lactone, indole, ionone. That “floral” scent of a good oolong comes not from additives but as a result of controlled injury to the plant.

Black tea. Full oxidation. Catechins are stitched together in pairs into theaflavins (orange-yellow, giving brightness and astringency) and then polymerise into thearubigins (red-brown, giving body and depth). Finished black tea contains roughly 1-2 per cent theaflavins and up to 20 per cent thearubigins. It is they, and not the catechins, that are responsible for the benefits of black tea, and that is a fundamentally different molecular story.

Pu-erh and dark teas. The only category in which the word “fermentation” is used correctly, because genuine microorganisms are at work. In shou pu-erh this is controlled wet piling with the participation of aspergilli; in Fu brick tea it is the fungus Eurotium cristatum, the “golden flowers” that are prized as a mark of quality. Catechins almost disappear, gallic acid rises, theabrownins are formed.

Part twoMedical

Theanine

L-theanine is gamma-glutamylethylamide, an amino acid that occurs almost nowhere else in nature. It was discovered by the Japanese chemist Sakato in 1949. In the tea leaf it accounts for up to half of all free amino acids.

Theanine crosses the blood-brain barrier, raises alpha-rhythm power on EEG 30-45 minutes after intake, modulates glutamatergic transmission and reduces the sympathetic response to caffeine. Hence the fundamental difference between a cup of tea and a cup of coffee: at comparable caffeine levels, tea gives focus without tachycardia and without the subsequent crash. In studies, the combination of roughly 50 mg caffeine plus 100 mg theanine consistently improved attention in task-switching better than either component on its own.

A rare fact that explains the price of Japanese tea. Theanine is synthesised in the roots and rises into the leaf, and in light it is converted into catechins. That is why, two or three weeks before harvest, gyokuro and matcha bushes are covered with nets. The light is cut off, the conversion does not take place, theanine accumulates. The result: a sweet, umami, “calming” tea instead of a bitter one. Shade quite literally rewrites the biochemistry of the leaf.

Catechins and EGCG

Epigallocatechin-3-gallate is the most studied polyphenol of green tea. Antioxidant action, an effect on the endothelium, a modest thermogenic effect, modulation of proliferation signalling pathways.

Theaflavins and thearubigins

Black tea has an evidence base of its own. There are data on a faster return of cortisol to baseline after acute stress in regular black tea drinkers. There are meta-analyses on a moderate reduction in blood pressure and on the lipid profile. Theaflavins are poorly absorbed as such, but they work actively in the gut lumen and are metabolised by the microbiota.

Pu-erh theabrownins

A 2019 paper in Nature Communications demonstrated an elegant mechanism in mice: pu-erh theabrownins alter the composition of the microbiota and suppress bacterial bile salt hydrolase, which increases bile acid excretion and forces the liver to spend cholesterol on their synthesis. Hence the lipid-lowering effect.

Every medicine has a side effect

Tea chelates non-haem iron. Tannins bind it in the gut, and absorption falls by tens of per cent. For a meat-eater without anaemia this does not matter. For a vegetarian woman, for a woman with heavy periods, for a child, it matters a great deal. The solution is simple: drink tea not with a meal but an hour later, and add lemon. Ascorbic acid simultaneously stabilises the catechins and reduces iron to an absorbable form.

Fluoride and aluminium. The tea plant is a hyperaccumulator. It draws fluoride and aluminium out of the soil and stores them in the leaf, and the older the leaf, the more of them. In pressed brick teas, made from coarse late-season material, the concentrations are such that a distinct clinical entity has been described in Tibet and Inner Mongolia: skeletal fluorosis from brick tea. This has nothing to do with ordinary leaf tea, but matcha, where you drink the whole leaf rather than an infusion, deserves moderation.

Temperature. In 2016 IARC classified the consumption of beverages hotter than 65 degrees as group 2A, “probably carcinogenic to humans”, for oesophageal cancer. The data came from regions where scalding tea and mate are customary. Let the cup stand for five minutes. That is probably the most useful thing you can do with tea.

Medicines. Green tea catechins inhibit the OATP1A2 transporter, and in a study with nadolol the absorption of the beta-blocker fell dramatically. Vitamin K is practically absent from brewed tea, but in matcha it is present in an amount a patient on warfarin ought to know about. And the obvious one: tea caffeine adds to theophylline.

But the kidney stones story is a myth. Yes, tea contains oxalates. But large cohort studies show in tea drinkers not a rise but a slight fall in the risk of urolithiasis, because the volume of fluid drunk outweighs the oxalate load.

Part threeMy SYAO

1. The best flavour in tea is created by an insect. The muscatel note of second-flush Darjeeling and the famous Taiwanese Dong Fang Mei Ren, “Oriental Beauty”, are born from the bites of a leafhopper of the genus Empoasca. The damaged leaf switches on a defensive programme and synthesises hotrienol and specific diene diols that are absent from a healthy leaf. Plantations destined for “Oriental Beauty” are on principle never treated with insecticides. The farmer pays with his yield and prays for the pest.

2. Rinsing does not remove caffeine. The advice to “pour off the first infusion after 30 seconds to reduce caffeine” has been circulating on the internet for decades. Measurements show that about ten per cent of the caffeine leaves in that time, while a substantial share of the aroma and the amino acids leaves with it. You pour away the best and the caffeine stays.

3. Cold water changes not the strength but the composition. Caffeine and the most bitter galloylated catechins are extracted well only by hot water. Theanine and simple sugars come out in the cold as well. So tea steeped overnight in the fridge is not “weak tea” but a different tea: sweet, free of bitterness, with a relatively higher proportion of theanine and noticeably less caffeine. Perfect for the evening.

Part fourGurian tea

The first tea bushes in these parts were planted in the middle of the nineteenth century, and they were planted as an amusement: an exotic plant for the princely gardens of Guria and Mingrelia. Then private need intervened. A European who settled here after the Crimean War, described by the sources as either an Irishman or a Scot, discovered that there was nowhere to buy tea in the Transcaucasian backwoods, and solved the problem radically: he laid out plantations of his own in the district of Ozurgeti and Chakvi. As early as 1864 his product was shown at a Russian industrial exhibition under the name “Caucasian tea”.

The real breakthrough came at the end of the century, when the Chinese master Lao Jinjao was invited to Chakvi. His tea was awarded a gold medal at the World Exhibition in Paris in 1900. This is worth taking in: tea grown on the 42nd parallel, at the latitude of Vladivostok and northern Spain, took world gold in competition with China and India.

In 1930 the Research Institute of Tea and Subtropical Cultures was opened at Anaseuli near Ozurgeti. It was there that agronomy, breeding and processing were worked on for decades; Georgian varieties such as Kolkhida came out of it, and out of it too, as we shall see, came one very unexpected bottle.

What followed was Soviet industrialisation with all its pluses and minuses: tens of thousands of hectares, the plan, machine harvesting, a bet on volume. And then the nineties, and the plantations were simply abandoned. The bushes went wild, became overgrown, but did not perish: tea lives a hundred years and more. Since 2016 a state rehabilitation programme has been in force; the plantations are being cleared, pruned, brought back into use. In parallel a completely new wave has appeared: small farms, craft production, speciality tea, sometimes founded by incoming enthusiasts.

In this whole story Guria is the central place. The institute, the oldest plantations, and the best raw material.

Geno and Georgian matcha

We were introduced to Geno by our guide in Georgia, Masha Zhemchuzhnaya. His father runs a huge tea estate in Guria, and an experiment is now under way there that I had no idea about before the trip: they are growing tea for matcha.

In recent years the world has been swept by a matcha shortage: demand has grown several times over, while tencha, the raw material for it, is produced in only a few Japanese prefectures, the harvest comes once a year, and expanding it quickly is physically impossible. Georgia, on the other hand, has land, climate, hectares and enthusiasts.

Incidentally, between “growing green tea” and “growing matcha” lies a whole abyss.

Cultivar. Japanese matcha is made from cultivars bred for a hundred years for one property: maximum theanine with minimum bitterness. Samidori, Okumidori, Asahi. These are clones; the plantation behaves as a single organism. The Georgian inheritance is arranged the other way round: seed populations of Chinese origin plus local selections chosen for frost hardiness and yield, because the task was to survive at minus ten. Seed propagation means genetic variegation; neighbouring bushes give different leaf.

Light. Uji is the 35th parallel plus the river mists that historically suggested the idea of shading to the Japanese. Guria is the 42nd parallel: a longer summer day, a different spectrum, a fiercer direct sun. So the shading scheme cannot be copied, it has to be recalculated from scratch. Three weeks under netting in Japan and three weeks under netting in Guria will yield different theanine. That is precisely the subject of the experiment.

Hardware. What had to be created was not only a new growing technology but new processing machinery too. First, the tencha-ro, a special oven in which the steamed leaf is dried without being rolled. Second, and most important, the stone mills. A granite pair grinds thirty to forty grams of matcha an hour. It is precisely the slow grinding without heat that gives a particle of five to ten microns, the emerald colour and the creamy texture. A ball mill or a jet mill heats the powder, gives a larger particle of a different shape, the colour shifts towards olive, and bitterness appears in the taste.

Industrial tea vs collection tea

Industrial tea is made like this. The machine cuts the whole flush: three, four, five leaves together with the lignified stem. Material from different plots and different varieties goes into a common stream. Then, in the classic industrial scheme, the leaf is torn and crushed (the CTC technology), oxidised quickly, dried quickly at high temperature. At the end the product is blended so that the pack in March and the pack in November taste the same. The goal here is not an outstanding flavour but reproducibility and price. The buyer wants it to be the way it was yesterday.

Collection tea is made the opposite way. Hand-plucking of the bud and one or two leaves, a specific plot, a specific day, no blending at all. The difference between harvests is not a defect but the essence of the product, as it is in wine.

• The bud and the first leaf contain the maximum of free amino acids, including theanine, and the minimum of fibre. The fourth and fifth leaf with the stem contain less theanine, more coarse fibre and appreciably more fluoride and aluminium, because accumulation increases with the age of the leaf.
• Crushing in CTC destroys the cell structure and ensures rapid extraction of thearubigins. The colour comes out powerful, but the volatile aromatics, that same linalool and its relatives, are largely lost. Hence the simple flavour of a teabag: strong but flat.
• Slow rolling of the whole leaf preserves both the structure and the aroma.

Gurian tea holds a collection-grade level.

In the laboratory attached to the factory they run a tasting that turns the process into something midway between a university lecture and a tea ceremony. And in the little shop they sell packets of tea you will not find in a supermarket.

The Bakhmaro tea extract

In the late 1970s, at that same institute in Anaseuli, a technology for liquid tea concentrates and tonic drinks based on them was developed. Production started in 1981, and in 1982 the development was awarded a state prize. The drink was named “Bakhmaro”, after the highland resort in Guria.

It is a fizzy drink made on tea extract, the answer to Pepsi-Cola, and in its day a genuine hit. Tasters described the flavour as sweet, with a cognac aroma and a creamy softness. The raw material, and this is especially elegant, was low-grade tea leaf: whatever was not fit for loose-leaf tea went into the extract.

The concentrate itself is a black, thick liquid, almost tar, which is diluted at roughly one to ten.

Unbelievably delicious!!!

Part fiveSeeds, oil and an impostor

Everything has been written about the leaves, while the fruits usually go unmentioned altogether. Naturally I asked the question: “And what can be made from the seeds?”

The tea bush flowers with white camellia-like blossoms and sets a dry three-chambered capsule holding one to three large seeds resembling hazelnuts. No flesh at all: the seed is stuffed with saponins and bitter to the point of being inedible. The flowers, by the way, are used: in China they are dried and infused, the taste is honeyed and cucumber-like, with almost no caffeine.

In Japan and China oil is pressed from the seeds. Cha you, camellia oil, is pressed mainly from the related Camellia oleifera. In southern China this is historically the principal cooking oil; it is called the eastern olive oil: about 80 per cent oleic acid, a smoke point of the order of 250 degrees, a neutral taste. In profile it is closest to olive oil, but it stands up to frying better. A separate branch is the Japanese tsubaki-abura from Camellia japonica, with which hair was cared for and blades were oiled against corrosion for centuries.

The cake left after pressing is full of saponins and is used as a natural detergent and as an ichthyocide: saponins destroy the gills of fish but do no harm to shrimp, which is exploited in aquaculture.

But the tea tree oil everyone knows has, as it turns out, no relation to tea whatsoever. Tea tree oil is Melaleuca alternifolia, an Australian myrtaceous tree, a relative of the eucalyptus. The name is a historical misunderstanding: the sailors of James Cook in the 1770s brewed melaleuca leaves instead of tea, and the confusion has been stuck in the language for two and a half centuries.

Part sixChoosing tea for each moment of life

When I come into the office, my husband does not simply offer me tea. He asks a question: “Which tea shall I brew for you?”

Because for every state and for different purposes – the tea is different.

• You need a clear head – Japanese green, shaded above all. Maximum theanine.
• You need to wake up – Assam black or a strong oolong.
• Evening, you want a quiet tea drinking – cold brewing or white tea with a short infusion.
• After a fatty dinner – shou pu-erh.
• You want an experience, a ritual – a medium-oxidised oolong. The aroma is more complex than in most perfumes.

And in conclusion, the important rules for creating a truly magical drink:

Brewing is not a ritual for the sake of ritual but the management of extraction. The main principle: caffeine and the most bitter galloylated catechins pass into the water the more readily the hotter it is, while theanine and simple sugars come out at a low temperature as well. Everything else follows from that. If you want a soft, sweet, relaxing infusion, lower the temperature. If you want vigour and astringency, raise it.

Temperature by type:

Gyokuro and shaded Japanese greens: 50-60 degrees. That is, almost warm water.

Sencha and other Japanese green: 60-70.
Chinese green and yellow: 75-80.
White from buds: 80-85. Aged pressed white already takes boiling water.
Oolong: 90-95, and a heavily roasted one all of 100. The volatile aroma of an oolong will not open without a high temperature, and a gentle regime ruins everything here.
Black: 90-95.
Pu-erh and dark: 95-100.
Matcha: 70-80, and this is not brewing but whisking a suspension. Two grams to sixty millilitres, with a whisk in a W-shaped motion, not in circles.

The quality of the water plays a very important role. The ideal is soft water, with a mineralisation of about 30-50 mg per litre. Calcium and especially bicarbonates raise the pH, oxidise the theaflavins and produce that iridescent film on the surface. Distilled water is bad too; entirely without ions the extraction goes wrong. If tea at home has suddenly stopped tasting good, check not the tea but the water.

Time and proportion:

The European tradition: 2-3 grams to 200 ml, three minutes, one infusion. The gongfu tradition: 5-7 grams to 100 ml, the first infusion 10-20 seconds, then increasing, eight to twelve infusions.

The difference lies in the fact that the substances come out sequentially. Amino acids and caffeine are extracted quickly, catechins more slowly. With short infusions you get the first cup sweet and invigorating, and by the fourth almost all the caffeine is already behind you, leaving flavour without stimulation. With a three-minute brew everything tumbles into one cup at once.

Useful details

Warm the vessels. Cold porcelain eats ten degrees off boiling water instantly, and you end up brewing at a temperature quite different from the one you had in mind.
Do not brew green tea in metal. Iron ions bind with the polyphenols, the infusion darkens and takes on a metallic tang.
Add lemon to tea that has cooled. In boiling water ascorbic acid is destroyed within minutes, and the whole point of lemon is precisely that acid.
Cold brewing: 10 grams to a litre, eight to twelve hours in the fridge.