tea leaf as a lab
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The chemistry of tea: a lab, not a leaf

The simplest way to understand what produces the differences among teas is through a short semi-science tutorial: Tea as a chemistry lab. The leaf is anything but inert. It’s a store of “odorous” molecular compounds – over six hundred – that offer a wealth of possibilities in how they can be nurtured, combined, diffused or dissipated through heating, drying, rolling, and in some instances infusion of flower petals. It’s this Artisan craft that produces the rich complexity of flavors and variety of aromas and aftertastes of fine tea.

The alchemy of tea making

Overseeing and managing the lab demands complex skills and experience. The Artisan tradition of tea making is rather like alchemy. It is science in practice, evolved through long experiments and learning. The medieval alchemists are often seen as frauds or buffoons trying to turn lead into gold. In fact, they were brilliant technicians who found out what worked even with no theoretical base to draw on. That base is emerging but scientists are only beginning to find their way around the lab; it is very dynamic and complex and reveals its secrets after long search.

The Alchemist tea masters (gender roles have been very, very marked in this ancient industry, together with caste and tribal boundaries) have evolved a meticulous expertise. They offer experience rather than formal principles. This is exquisitely fine-tuned to every detail of context, conditions, timing, and even individual patches of plants.

Of course, just as you don’t have to draw on the comparable magic touch of a gourmet chef for your dinner but can microwave a decent prepared frozen meal, you can bypass the alchemist. The Agribusiness mainstream of tea greatly streamlines and simplifies the journey of your tea from bush to cup. Tea bags, machine harvesting, crush-tear-curl leaf preparation instead of “two leaves and a bud” plucking, additives, flavorings and bulk shipments and custom custom blending are tools in this largely cost- and volume-driven mass market tea. It corresponds to prepared foods.

This transforms the lab. The “product” may remain the same in name and description but it its chemistry is very different, though not necessarily “better” or “worse.” But, for example, an Assam breakfast tea, an Earl Grey blend or a China green tea may be alchemist-leveraged or agribusiness-reduced in its use of the tea lab. In almost every instance, something gets lost. Price, familiarity, reliability and convenience may compensate for this (like “defrost, place in microwave, heat for 2 minutes” does) but here’s the core distinction that basically drives the entire tea industry:

Artisan: Activate the compounds for whole leaf variety
Agribusiness: Reduce them for mass market cost and efficiency

This gets glossed over in much of the marketing of teas. Take, for example, the Assam breakfast or Earl Grey mentioned above. Do you know if it’s machine-processed CTC — Cut, Tear and Curl — or hand plucked? Why should you care? The answer is simple: there is no way that the CTC can match the quality and taste of the two leaves and a bud one.

How much does geography matter?

Where the bush is grown is the single major determinant of the specific contents of the lab. Soil, weather, roots, farming methods, seasons, slopes and even insects build the leaf-lab. The chemical compounds in the leaf begin their reactions within an hour or less of being plucked, so that they must be processed quickly. With the high-end specialty teas of elite reputation, tea gardens exploit every nuance of weather and moisture – and even time of day – in plucking, minutes in timing of processing steps and in forming the finished leaf. There’s a whole craft of trading off the length and smoothness of a Darjeeling tip to maximize its floral aroma, for instance.

Biodynamic methods contribute to the lab in many indirect ways, including manuring, pruning cycles, the number of bushes planted per acre and how to provide the nitrogen and trace elements needed by the leaf lab through composting rather than artificial fertilizers. (Biodynamics is the broader and more accurate term for organic farming, which is very much a labeling issue that smaller growers cannot afford, because of the costs and bureaucracy of certification.)

Early season harvests are much higher in the ones that contribute most directly to health value and shelf life. Late harvest teas bear the same name and look the same but are chemically inferior. They may lack some of the lab ingredients that contribute to fullness and body or be high in others that add bitterness. African teas that are increasingly major ingredients of mass market blends are in many instances lower in polyphenols, the main determinant of the health value of a tea, but higher in the chlorophylls that add richness of color. This is especially so for Malawi teas. These offer less quality but improve the attractive appearance.

The main ingredients for a tasty and healthy tea

Tea is packed with polyphenols, a type of antioxidant, that attack and detoxify cell-damaging free radicals in the body. Free radicals are unstable molecules that can bind to other ones; many are introduced into the body by pollutants, smoking and ultraviolet radiation. Antioxidants have been pithily described as like the busy little “Pac man” game icons chasing down and gobbling up the radicals. Polyphenols are the main store of time-release compounds that very subtly build the texture, astringency and “body” of the tea taste. They break down into catechins, and theaflavins and thearubigins. Very roughly, catechins contribute to the lightness and sweetness of the tea and the others to its fullness and boldness.

The composition of the tea leaf.

The composition of the tea leaf.

Catechins constitute 25% of the weight of the dry leaf and include many tongue twister terms and acronyms that are permutations of EGCG (Epigallocatechin gallate). These differ at the level of individual molecular binding and their formations and relative volume are widely referred to in ads for green teas. Studies consistently show that minor variations in seedlings, clonal tea varieties, elevation and seasonality greatly affect catechins, which determine most aspects of black tea aroma, flavor, mouth fill and aftertaste.

What does this mean for you?

The most relevant message for tea drinkers here is that all the chemical interactions translate to impacts on flavor, texture, taste, aroma, brewing – well, everything. In many ways, the craft of tea has been an evolution of which of the everythings gets turned into our thing – the special names like Mao Feng, Castleton Moonlight, or Longjing Dragonwell. They explain the many distinctive characteristics of a Darjeeling first flush versus the subtly different second flush harvest from the very same bushes, just a few months apart. Same lab, different chemistry.

Three quarters of the plucked leaf is just moisture and one of the first steps in processing is to gently reduce that through withering. (White tea bypasses this.) The nonsoluble carotene, chlorophyl and cellulose build the leaf’s structure, healthiness and color. It’s the soluble compounds that make tea really interesting in its science and practical dynamics. These build up, are released, combine, dissolve and interact in stages.

Some, for instance, become activated in the very first step in processing, the withering that removes excess moisture. Others are brought out in the rolling that breaks up the cellular structure of the leaf. Many are sensitive to a few degrees of change in external temperature, daily shifts in moisture on the bushes, a half minute of brewing time, and the craft by which the chemical reactions are balanced and optimized.

The best teas exploit the extraordinary range of compounds and how they are combined and balanced. The average ones narrow them down in the interests of cost and ease of processing. If the leaf is machine harvested, some of the chemical potential disappears. If it’s crushed, the enzymes are in essence beaten up and their subtle interactions stopped. When the processing homogenizes the leaf, mixes in soy lecithin and a cheap flavoring additive… You get the point.

You’re paying for expertise in managing molecules

In making your own choices of tea, it may not make be of any real value to your selection to know about the intricate details of processing. That said, there some general points worth considering. The first is, does the alchemy really matter? The answer to that is “Yes. Big time.” The variations that make one Darjeeling, say, stand out as really special versus another that is not quite as appealing come from distinctive skills and meticulous customization of leaf and method. The same applies to what makes white teas so exquisite and savory and oolongs so multi-dimensional in their body, flavor, balance of tastes and aromas.

The craft of tea making is not yet science; there is still much about teas that is a topic for research, new methods of molecular analysis are being developed, and the molecular structures and interactions tracked. But there’s a growing body of knowledge that is bringing out the scientific grounding and principles underlying the tea makers’ intuitions. The science is emerging via such tools as gas chromatography, spectrometry, DNA marking and molecular analysis. In essence, it confirms that the skilled crafters of tea have got it right.

Respect the alchemy and the chemistry in choosing the teas that offer more than just a wet and warm hydration. It’s not snobbery to prefer a hand-plucked Darjeeling over a CTC Assam. Cheap bagged green teas from Argentina and Korea can tart up their labels with poetic piffle about the proven benefits of ECGC and anti-oxidants but the chemistry of that third and fourth leaf just won’t match the prose.
Taking leaf from twenty countries and bulk shipping it to Dubai (where half of all Lipton tea bags are “made”) and then blending them with added pomegranate and adding a soy lecithin emulsifier doesn’t change the apparent nature of the tea and it often retains the same high end name. But the chemistry is not quite the same as if it’s whole leaf, biodynamically farmed and artisan-processed. Most of all, your following the recommended rules of brewing makes the chemical formula effective: for black, boiling water, 3-5 minutes down to green at 175 degrees, maximum of 3 minutes. Use a microwave and you leave the world of chemistry for physics and thermodynamics.

So, it’s well worth buying whole leaf tea made in the tradition of two leaves and a bud hand plucking, favoring the gardens and estates that have a long-established reputation, being wary of blends and flavors, and brewing your tea carefully. As a well-known singer stated “The one thing you can’t fake is chemistry.”

Featured banner illustrated by Tasneem Amiruddin

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  • Peter GW Keen
    Peter Keen has been a professor at leading universities across the world, including Harvard, MIT and Stanford in the US and in Singapore, The
    Netherlands, Mexico and UK. He is the author of over thirty books on the links between business innovation and technology.
    Peter was born in Singapore, brought up in England and now lives in Virginia in the US.

    Peter loves tea and loves writing. His latest book, Tea Tips: A Guide to Finding and Enjoying Tea was published in February 2017.
  • All Posts from Peter GW Keen

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