Last week, I talked about how all tea comes from the same plant: camellia sinensis (and its varieties). I got a bit excited sharing how tea is grown, how it’s plucked and when it’s harvested and ran out of time/space/your attention span to explain how we end up with black, green, white and oolong tea. As they are such distinct yet delicious varieties, I’ve decided to dedicate a post to each one. So here we are: black tea.
In order to obtain the dark brown liquor we all love so much, tea leaves go through four stages once they are plucked: withering, rolling, oxidation and firing.
Similar to the way your flowers or herbs wither in hot weather after they’re picked, leaves react in the same way. It’s a natural process that traditionally occurs by exposing tea leaves to sunlight; they’re arranged in thin layers on bamboo or wire trays so that every one of them can sunbathe in style! However, you can imagine that for large productions this is unfeasible, so the leaves are instead transferred to temperature controlled rooms and kept between 20-24 degrees Celsius, with good ventilation.
The leaves will be left to relax and wither for 18-30 hours depending on the climate.
Now that the leaves have softened, they are more flexible so the rolling process can begin. This is done to break down the cells to release an enzyme which helps with oxidation. And, as you’ve probably guessed, the more you roll them, the quicker oxidation will happen. This can be done manually or mechanically and the length of time it’s performed depends on things like the leaf quality, the time of the year, the temperature and the climate.
This stage also determines the body of the cup – gently rolled leaves produce a light tea, whereas vigorously rolled leaves have a fuller, stronger body.
What is the body of a tea you ask? Well, the first sign will be the colour: light = pale and full = dark(er). Then it’s also the taste, light teas are generally mild, whereas full bodied teas have a much stronger, pronounced taste (this is your English Breakfast).
If withering was necessary to remove the water from the tea leaves, one of the crucial points with oxidation is that the humidity needs to be maintained between 90-95%. The leaves are again spread so they can all get the same treatment and the enzymes start to change the chemical composition, turning them the familiar dark red/brown colour.
The temperature also needs to be closely monitored as if it drops below 20%, the oxidation slows down or stops, and if it goes about 22% the leaves are ‘burned’.
It’s not actually as harsh as it sounds! I’d probably call it baking but ‘firing’ is the official term. This is done by exposing the leaves to temperatures of about 90 degrees Celsius for around 20 minutes which will both dry out the moisture left and kill the enzymes to stop oxidation. Tea manufacturers have to be careful with this process because if they don’t run it for long enough, the leaves could become mouldy. And if they run it for too long, the resulting brew will lack flavour. The leaves should have about 5% water left in them for a decent cuppa!
So, what do you think? Once I found out all of this years ago, I couldn’t look at a cup of tea in the same way! And wait until you discover how the green, white and oolong teas are formed.
Until next time!