If you have ever taken a sip of black tea and noticed a slight drying sensation on your tongue, you have experienced tannins at work.
Tannins are often mentioned in discussions about strong tea, acidity and digestion, yet they are frequently misunderstood. Some people associate them with bitterness. Others blame them for stomach discomfort. In reality, tannins are natural plant compounds that play an essential role in tea’s structure and character.
Understanding tannins helps explain why Assam black tea feels bold, why brewing time matters, and why perceived acidity is not always what it seems.
If you would like a broader foundation on Assam tea’s origin and craftsmanship, our Ultimate Guide to Assam Tea provides the wider context behind the leaf.
What Are Tannins?
Tannins are a group of polyphenolic compounds found naturally in many plants, including tea, coffee, wine and certain fruits.
In tea, tannins are primarily formed during oxidation. When tea leaves are rolled and exposed to oxygen, naturally occurring catechins transform into larger compounds known as theaflavins and thearubigins. These compounds contribute to:
- Colour
- Body
- Astringency
- Structure
They are not artificial additives or processing chemicals. They are part of the leaf itself.
Tannins and Astringency: Why Tea Can Feel Dry
The sensation most commonly associated with tannins is astringency.
Astringency is not the same as bitterness. Bitterness is a taste. Astringency is a tactile sensation.
When tannins interact with proteins in saliva, they reduce lubrication in the mouth. This creates the slightly drying or gripping feeling often described as strong.
Assam tea, particularly when brewed robustly, contains enough tannins to create structure and depth. This contributes to its satisfying body and ability to stand up to milk.
If you would like to understand why Assam tea tastes bold even when it is not highly acidic, our article on why Assam tea tastes so strong explores the interaction between leaf chemistry and flavour perception.
Do Tannins Make Tea More Acidic?
This is a common misconception.
Tannins do not significantly increase acidity in the chemical sense. Acidity refers to pH level. Tannins contribute more to astringency than to measurable acidity.
In our article on whether Assam tea is acidic, we explain that black tea typically falls between pH 4.9 and 5.5, which is mildly acidic but far less acidic than coffee or fruit juice.
The drying sensation caused by tannins can be mistaken for sharpness, leading some people to assume the tea is highly acidic when it is not.
How Brewing Time Affects Tannins
Brewing has a direct influence on tannin extraction.
Shorter brewing times extract:
- Aromatics
- Some caffeine
- Light structure
Longer brewing times extract:
- More tannins
- More polyphenols
- Greater body and dryness
This is why over-steeped tea can taste harsh or feel rough in the mouth. It is not that the tea is lower quality. It is that more tannins have been drawn out of the leaf.
If you prefer a gentler cup, reducing brewing time slightly can soften the sensation without sacrificing flavour.
Our guide on how to brew Assam tea properly and simply explains how to adjust strength intuitively rather than rigidly.
Do Tannins Affect Digestion?
Tannins can interact with proteins and digestive enzymes. In moderate amounts, they are not harmful. In fact, tannins have been studied for their antioxidant properties.
However, very strong tea consumed on an empty stomach may feel uncomfortable for some people. This is often due to a combination of caffeine and tannins rather than acidity alone.
Our article on whether Assam tea is good for digestion explores how brewing strength and timing influence comfort.
For most people, drinking Assam black tea with or after food reduces any potential digestive irritation.
Tannins and Milk: Why They Pair Well
One of the reasons Assam black tea works beautifully with milk is because milk proteins bind to tannins.
This binding softens astringency and creates a rounder mouthfeel. It is not masking acidity. It is moderating tannin perception.
This is also why Assam black tea is commonly used in breakfast blends and masala chai.
If you are curious about this pairing in more detail, our article on whether you can drink Assam tea with milk explores how structure and body interact with dairy.
Are Tannins a Sign of Quality?
Tannins themselves are not a measure of quality. All black teas contain them.
What distinguishes high quality tea is balance. In good quality, well-made Assam tea, tannins provide structure without harshness. In poorly processed tea, tannins can dominate and feel sharp or bitter.
Leaf quality, plucking standard and oxidation control all influence how tannins express themselves in the final cup.
The article How Assam Tea Is Made, which explores the journey from plucking through oxidation and drying, explains how production choices shape these compounds.
Should You Avoid Tannins?
For most healthy adults, tannins are not a problem and are part of what gives tea its satisfying character.
If you are sensitive, simple adjustments help:
- Brew slightly shorter
- Avoid drinking very strong tea on an empty stomach
- Add milk if you prefer a softer cup
Tannins are not something to fear. They are part of the structure that makes Assam tea distinctive.
Tannins Are Part of the Architecture of Tea
Rather than viewing tannins as something negative, it is more accurate to see them as part of tea’s architecture.
They create shape, texture and depth. Without them, Assam tea would taste flat and thin.
Understanding tannins helps demystify strength, acidity and mouthfeel. It also reinforces that boldness in tea comes from chemistry and craft, not from excess acidity.
To explore how leaf variety, oxidation and environment shape these compounds from the start, return to our Ultimate Guide to Assam Tea, where the full story continues.