“Oh chemis-tea, oh chemis-tea,
This stanza is a creative derivation on the classic Christmas carol “Oh Christmas Tree.” Written in 1824 by Ernst Anschutz, and originally titled “O Tannenbaum.”
Chemistry is an integral part of what you are drinking in the cup. When you take a sip of tea, you are tasting some of the various elements of chemistry that have been manipulated to create this globally sought after drink.
Soil And Land Chemistry
Before tea leaves are plucked, the land the plant is growing in plays a critical role in the chemical properties of the tea leaf. “Terroir” is a term used with wine and tea professionals alike. The term means the soil content, topography of the land, altitude, weather patterns and climate that can affect the chemical properties in the leaf (or the wine grape).
Black, green, white, yellow, oolong or dark tea are processed from leaves harvested from the evergreen Camellia Sinensis bush. Where the leaves are plucked on the stem and how long the leaves have been on the Camellia Sinensis bush can vary some chemical properties in the leaf affecting color, aroma, and taste of the tea. Plucking the outer two leaves and a bud usually denote a higher quality of tea that is delicately flavored. Leaves that are farther down on the stem are mature growth, and produce a more robust taste in the cup.
There is a chemical in the leaf called chlorophyll. Regulating, controlling, or manipulating the amount of sunlight the Camellia Sinensis is exposed to affects the amount of chlorophyll the leaf produces. In Japan, some tea plants are shade grown for the last few weeks under a shade arbor. This is done in order to increase the amount of chlorophyll the plants produce. Translated in the cup, the extra chlorophyll is what gives the Matcha and Gyokuro liquor it’s bright green color, a thick mouth feel, and typically a sweeter tasting tea.
A chemical change immediately occurs the minute the tea leaves are plucked; they start to wither and lose their moisture content. The moisture content in the leaf is manipulated during the withering stage. Depending on what type of tea will be processed, the leaves are either quickly dried or they are left to wither for hours. Due to withering the leaves become softer, more pliable and able to withstand handling, shaping, or rolling without tearing. A long wither can bring out more pronounced flavor and fragrance profiles in the cup.
Oxidation is the process that turns the tea leaf brown, affecting the taste, aroma and liquor color of the tea. Oxidation occurs when the ambient oxygen in the air changes the enzymes in the leaf cells. The same chemical reaction happens in a cut apple, turning it brown. The plucked tea leaves become increasingly brown in color the longer the leaves are left to oxidize. Black tea has the longest oxidation time creating an amber color, a complex aroma, and a fuller bodied cup of tea. Oolong tea has less oxidation time than black tea and its color can vary from an amber to pale green-yellow color. Traditionally there is no oxidation time for green and white tea.
Let’s go back to the cut apple example. In order to stop the cut apple from turning brown, heat is utilized. Heat is applied to the leaves just like the apple, in order to stop the leaves turning brown due to oxidation. Green tea leaves are either pan fired, or steamed to stop the oxidation process. This is referred to as de-enzyming the tea leaves. China historically uses pan firing and Japan is noted for steaming the tea leaves. The cessation of the oxidation process in green tea leaves permits the tea to retain a more green color in the cup, and a vegetal flavor profile.
Shape Of Leaf
The size and shape of the tea leaf can affect the taste in a cup of tea. A tea leaf that is cut, torn, and curled into fragments has a larger surface area to mass ratio than a whole leaf. The larger the surface area to mass ratio, the more exposed the leaf enzymes are and the quicker the chemicals in the leaf are released in water. A leaf that is rolled tightly into a ball, oolong tea for example, has a lower surface area to mass ratio. The oolong leaf unfurls more with each steeping; increasing the surface area ratio of the leaf and releasing subtle flavor profile complexities.
Chemistry is foundational to tea. Actually, chemistry is fundamentally tea. The amount of information provided has been greatly simplified so that information overload can possibly be avoided. The information is not a complete list of the chemical reactions that occur in the world of tea. The information is an overview, an introduction to the complexities of tea. Future writings can delve more deeply into each stage of processing tea. Next time a cup of tea is steeped, take a moment and revel in the fact that you are now a scientist. You just had a rudimentary crash course in “Chemis-tea!”
About The Author
Leslie Sundberg is a World Tea Academy Certified Tea Specialist, a World Tea Academy Apprentice Tea Sommelier, a Specialty Tea Institute Level IV trained Tea Specialist, and a Tea and Business Etiquette Specialist. On any given day, Leslie can be found teaching, speaking or sharing in the joys of a cup of tea. No matter what Leslie is doing or where she is, one thing remains constant: 4:00 in the afternoon is tea time!