In many cultures, you must have seen that people boil tea. I have witnessed the same. This practice is followed even in the regions where loose leaf/orthodox tea is produced. But boiling loose leaf tea yields bitter tea and perhaps it is not a good idea unless you are drinking that tea with milk or milk and sugar/sweetener.
Picture: A Nepali household boiling Milk and Tea on the fire
People prefer drinking malty teas with Milk and Sweeeteners and floral tea without any adding anything. Same goes with Green Tea. Steep too long and you know that Green Tea becomes too bitter. Let alone, boiling is the worst case to go in the case with green tea.
In this blog, I will share the detailed information about boiling and steeping and the process that happens when in each individual process. From there, we will deduce why boiling high quality loose leaf is wrong.
But First, Lets have a quick chat about High-Quality loose-leaf Tea?
What is High-Quality loose-leaf Tea?
Often called whole leaf tea, high quality whole leaf tea is determined by characteristics like wholeness of the leaf, aroma, liquor color and taste, mouth fullness etc. They are treated as prized products by tea connoisseurs around the world.
Extraction of the liquid from this tea is often done by a process called steeping, which we will discuss in the segment below.
What is Tea Steeping Process?
Tea Steeping is the process of making liquid tea from tea leaf by addition of water at a certain temperature. Depending upon the type of the tea, steeping time and temperature of the tea varies. This is often done using accessories like Tea Pot (Western Method) and Gaiwan (Chinese Method).
What happens when you add hot water to tea leaf?
When you add hot water to the tea leaf, the following chain of events happen:
Initial Contact between water and Tea leaf
When the hot water comes in contact with the loose-leaf tea, it begins to infiltrate the leaf structure. This happens as the heat causes the cell walls of the tea leaves to expand and the leaf structure becomes more permeable. Permeability means the ability of a substance to let liquid or gas pass through it.
Osmosis initiation:
A concentration gradient forms between the water and the interior of the tea leaves. This triggers osmosis, where water molecules start moving from an area of higher concentration (the hot water) to an area of lower concentration (inside the tea leaves).
Cellular breakdown:
As the hot water continues to penetrate the leaves, it causes some of the cell walls to rupture. This breakdown releases various compounds stored within the leaf cells.
Soluble compound extraction:
The hot water acts as a solvent, dissolving and extracting water-soluble compounds from the tea leaves. These include:
- Polyphenols (including catechins, which give tea its astringency and potential health benefits)
- Caffeine
- Amino acids (like L-theanine, which contributes to tea's umami flavor and calming effects)
- Carbohydrates
- Minerals
Color change:
As these compounds are extracted, they begin to color the water. The specific color depends on the type of tea (e.g., black, green, oolong) and is primarily due to polyphenols and their oxidation state.
Volatile compound release:
The heat also causes volatile organic compounds to be released from the leaves. These aromatics contribute to the tea's scent and flavor profile. This is when the brew starts giving out aroma.
Oxidation:
Some compounds, particularly in black and oolong teas, undergo further oxidation when exposed to the hot water and air. This can alter the flavor and color of the tea.
The main reason behind this is: Black and Oolong teas extract/liquid have chemicals in them which have tendency to be oxidized when they come in contact with the air. This is the main reason why some of the tea liquor get more darker and darker as you leave them in your tea pot/cup for a long time(even after taking out the tea leaves. Same goes with the steeped tea leaves, leave them long enough exposed in the air and they turn darker.
Ongoing extraction:
The extraction process continues as long as the leaves remain in contact with the hot water. However, the rate of extraction slows over time as the concentration gradient decreases.
What does it mean: It means after the certain period of time, the difference in concentration between the contents of the cell and the water it is in cease to exist. When there is no concentration difference, there is no more extraction of contents from the cell of the tea leaves.
Cooling effects:
As the water cools, the rate of extraction slows down. Different compounds extract at different rates depending on water temperature, which is why specific tea types have recommended brewing temperatures.
What does this mean: There is always an optimal temperature for certain chemical extraction. Increasing the temperature beyond that results significant reduction of compounds due to their degradation.
Equilibrium:
Eventually, if left long enough, the system would reach a state of equilibrium where the concentration of extracted compounds in the water matches that remaining in the leaves. This optimum time where the contents of the cell and the water reach the equilibrium is called “Steeping Time of the Tea”.
Step 1 to 10 explains what happens during the steeping process and why it is crucial to maintain the time and temperature when steeping a high-end loose-leaf tea.
Now what happens if you boil the same Tea?
The following thins happen when you boil the tea instead of steeping it.
Rapid extraction:
Boiling water (100°C/212°F) causes a much more aggressive and rapid extraction of compounds from the tea leaves compared to steeping at lower temperatures.
Over-extraction of tannins:
The higher temperature extracts more tannins (a type of polyphenol) from the leaves. This results in a much more bitter and astringent taste, often described as "overcooked" or "stewed."
Destruction of delicate compounds:
Many of the more delicate flavor compounds and aromatic volatiles are damaged or destroyed by the intense heat. This is especially true for green and white teas, which are typically brewed at lower temperatures to preserve these compounds.
Loss of nuanced flavors:
The subtle, complex flavor profile that makes each tea unique is often lost when boiled. The resulting brew tends to be more one-dimensional, dominated by bitterness and astringency.
Increased caffeine extraction:
Boiling extracts more caffeine from the leaves, potentially resulting in a more stimulating but harsher drink.
Protein denaturation:
Any proteins present in the tea leaves are likely to denature at boiling temperatures, potentially affecting the texture and mouthfeel of the tea.
Accelerated oxidation:
The higher temperature and agitation from boiling can accelerate oxidation reactions, particularly in green teas. This can lead to off-flavors and color changes.
Mineral concentration:
Extended boiling can increase the concentration of minerals extracted from the leaves, potentially affecting both flavor and the mineral content of the final brew.
Physical breakdown of leaves:
Boiling can cause more extensive physical breakdown of the tea leaves, leading to more particulate matter in the final brew and potentially a cloudy appearance.
Vitamin degradation:
Many vitamins are heat-sensitive and may be partially or completely destroyed by boiling temperatures.
Potential formation of new compounds:
The extreme heat may catalyze reactions between various tea compounds, potentially forming new substances not typically present in properly brewed tea.
So not only boiling high end tea makes it bitter, you lose its aroma, intended taste and the nutritional value which beats the whole purpose of buying the high-end tea.
Conclusion, steep the loose-leaf tea and don’t boil it, if you want to enjoy it properly.
Written by:
Bhaskar Dahal
