Tea really heats things up when it comes to polyphenols
Let’s explore the food science theme a bit more from where we started in my earlier post Camellia sinensis: The Superhero Plant. So, here we go: Time for a brief foray into the big, sexy world of tea and polyphenols.
Tea leaves are rich in complex organic molecules (“polyphenols”) such as catechins, thearubigins, and flavonols. These are good to be familiar with as they play an important role in the health and the epicurean qualities of tea.
Oxidization is key in the world of black tea making. Imagine: you bite into an apple, leave it on the
counter for an hour. You then come back to see the reddish brown crater made by your big, sharp teeth. That’s the oxidization from the air plus your saliva’s enzymes (namely amylase) reacting upon the carbohydrates in the apple.
With that in mind, we see how the tannins associated with black teas and longer-oxidized oolong teas also come from this enzymatic oxidization process. Enzymes are proteins that, if left to do their bidding, allow for a visual browning and development of unique flavors in your tea. Think: malty flavor, ripe stone fruit, fresh mulch, caramel (I am by no means a tea sommelier, but I have a great respect for the nuanced language they use to describe flavor and mouthfeel). Here is where you start to also taste tannin too.
The polyphenol group “thearubigins” (which include “theaflavins”), are sometimes referred to as “tannins.” Scientifically, they are considered by molecular weight as “pseudo-tannins.” We notice the tannic quality of tea in terms of flavor and color profiles. Thearubigins and theaflavins are astringent and have red-brown hues that stain your teeth…. and teacups! Tea does not contain the specific compound “tannic acid,” a fun fact you can bring up to impress friends at your next tea party or when surrounded by chemists.
Operation: Green kill
Tea’s primary enzymes, including polyphenol oxidase, are active throughout the entire black tea recipe until they are denatured in the eventual later stages of heating and drying. By contrast, green tea, requires enzymes to be stopped within the early stages of its recipe to avoid this chemical chain reaction.
But, how to stop the formidable forces of enzymatic oxidation? Like this: The leaves intended for green tea are heated, either in a pan, or steamed (we’ve even seen it done in a microwave… tea purists have interesting reactions to that one). This heat vanquishes the enzymes, preventing oxidization going forward as we make green tea. The tea industry has adopted the less-than-endearing sounding term “green-kill” to describe this important step. So remember that one. Green-kill. Not a toxic herbicide, but a noble step in crafting an exquisite green tea.
Because of green kill, green teas (think: sencha, dragonwell, mao feng) are chemically different from their black tea cousins. They are very rich in catechins but not in tannins. These chemical differences in finished green and finished black tea allow for their variations in taste, color, and mouthfeel. Green teas are no less well rounded or delectable, yet they have astringency, and floral and vegetal notes without the taste of tannin.
I will not oversimplify the tea making process. Tea making and tasting is incredibly complex. Many other factors in tea farming and processing influence the polyphenol composition and the characteristics of your cup of tea. Examples include: rainfall for the plants, whether tea is shade or sun grown, processing steps such as withering, rolling, roasting, equipment, drying, grading, packaging. Humidity and temperature are key to keep an eye on in processing, packing, and storage (tea will mold if not properly dried). Any one of these steps or circumstances can help distinguish or ruin a tea.
Polyphenols in general, either from tea or other plants, have purported benefits for human health. The research on Camellia sinensis and human wellness is absolutely fascinating. On that note, we shall bid our sexy polyphenols aloha for now, and explore some of the research between tea and human health in my next post.
Thanks for reading and a hui hou!
Become a Tea Sommelier or Just Beef Up on your Tea Knowledge
Tea: History, Terroirs, Varieties
Tannin in Tea Overviews:
Tea and Human Health
Tannins and Human Health
Polyphenol Content of Tea
Classification of Tannins