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Tea is simple: loose-leaf tea, hot pure water, a cup.

I inhale the scent, tiny delicate pieces of the tea floating above the cup.

I drink the tea, the essence of the leaves becoming a part of me.

I am informed by the tea, changed.

—Thích Nhất Hạnh

I start my day by making a quick aqueous extraction of secondary plant metabolites. I stir in a few grams of a purified natural disaccharide, clutch the cup in my hands, inhale a hit of linalool, and take my first swallow of tea. Even if you’re not a chemist, you very likely start the day in the same way, making a cup of coffee or tea to enjoy its caffeine-fueled bite and heady aroma, even if you wouldn’t describe it in quite those terms. To be honest, even though I’m a chemist, I wouldn’t describe it that way either, at least not before the caffeine has kicked in.

This idea for this book grew out of a tweet. “Chemistry question for #ChemTwitter: is there an extractive advantage to the tetrahedral teabag over the traditionally shaped teabag? Or does it just look cooler?” mused @andrechemist. #ChemTwitter had thoughts, but I started to wonder if there was any published research about the effect of a teabag’s shape on the taste of the resulting tea. In fact, just what did chemists know about making a cup of tea? I was between two terms of teaching and so spent a couple of days rummaging around in the research literature to see what was known about the best way to make tea. Quite a lot, as it turns out, beginning with a mysterious woman chemist from the 19th century to chemists and physicists from all corners of the world in the 21st. And yes, there was research on the best size and shape for a teabag. Just before the start of the COVID-19 pandemic in 2020, I wrote a short essay for the journal Nature Chemistry about making the perfect cup of tea from a chemist’s perspective, from which this book ultimately emerged.

While that original article was written for chemists, this book is meant for tea-drinkers who may or may not be chemists. If you haven’t taken a chemistry course, or haven’t taken one recently, don’t worry. I’ve broken down the chemistry you need to know to safely plunge into the molecular world of tea and come out with a better cup. What is a saccharide? Why do I crave the aroma of linalool nearly as much as the buzz from caffeine? And, speaking of caffeine, what does the tea plant get from it? If you are a chemist, I hope you will delight in what follows as much as I did; there is a rich literature out there.

Each chapter begins with a tea pairing. I’ve given at least two options and tried to include ones that are more likely to be available at a local market, along with more specialty recommendations. Tea is a natural product and one of the joys is that every cup is different, depending on where and when the plant was grown and how it has been treated since. Even the local water used to brew the leaves can change the taste of the final brew, as we will see in Chapter 5.

Want to know more? Each of the chapters ends with a section entitled Going Further. If something in a chapter has piqued your interest, the resources here might be the next step in going deeper into the material. The books that I recommend are generally in print, widely available from booksellers and public libraries, and accessible to the general reader. Journal articles can be more difficult to access because publishers can charge quite a bit for the material. I have tried to select articles that are readable by a non-chemist and available for free. The Reference sections cite material from the primary literature that may be of more interest to those with a science background.

The bottom line is what can chemistry tell us about brewing a better cup of tea, whatever that might mean to each of us. Want to make sure you get every last bit of caffeine you can? Or is the calming floral aroma what you desire? What is the best way to keep a cup of tea hot on the way to work? Sections entitled Brewing a Better Cup have advice on how to get your optimal cup of tea based on the science of that chapter.

I read more than 500 papers while researching this book and drank at least 483 cups of tea (I didn’t start counting until I was partway through). I drank deuterated water, spiked my tea with l-theanine, and sampled tea with more than the usual amount of GABA. I wired my teapots and teacups with temperature sensors and measured cooling curves. I tried decaffeinating tea with vodka (not recommended). I did not scrape snow off the plum blossoms in my yard to melt for tea, despite the rave reviews in an 8th century manuscript.

A comprehensive review of the primary research literature on the chemistry of tea would require several volumes, so by no means should this book be considered the final word on all that scientists know about tea, its production, and its infusion. Instead, I have focused here on work that addresses the questions that interested me. I’ve had a great time steeping in the scientific literature about tea and hope this book will give you the eyes to see what’s hidden in your cup of tea too. I invite you to make a cup of tea, perhaps one that is paired with the chapter, and enjoy taking a dive with me into the molecular mash-up that is the world’s most popular beverage: tea.

Michelle Francl

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