Which Kind of Acid Is Present in Tea? Unveiling the Compounds Behind the Flavor

December 11, 2025 •

4 min read

Brewed tea typically has a mildly acidic pH between 5.0 and 6.0, reflecting its rich and complex chemical makeup. For those who have asked, "Which kind of acid is present in tea?", the answer is not a single compound but a fascinating blend of organic acids and potent polyphenols that contribute to its flavor, color, and health-promoting properties.

Quick Summary

Tea's acidity stems from a complex mix of organic acids and polyphenols, not a single compound. Key components include quinic, malic, and citric acids, along with powerful polyphenols known as tannins, which contribute to its characteristic taste and health benefits.

Key Points

Not Just Tannic Acid: The acidity in tea is not from a single 'tannic acid,' which is a commercial form, but from a complex mixture of many organic acids and polyphenols.
Complex Acidity Sources: Key organic acids found in tea include quinic, malic, and citric acids, all of which contribute to its tart and sour notes.
Tannin's Astringent Effect: The drying, bitter mouthfeel often associated with strong tea is caused by polyphenols known as tannins, which are different chemical compounds than tannic acid.
Processing Matters: The type of tea and its processing (e.g., green vs. black) significantly affects its acidic profile; black tea has different polyphenols like theaflavins due to oxidation.
Brewing Controls Flavor: Brewing time and water temperature directly influence the extraction of acids and tannins; longer, hotter brews typically increase bitterness and astringency.
Moderating Acidity: To reduce potential side effects like nausea or iron absorption issues, you can drink tea between meals or add milk, as proteins bind to tannins.

The Surprising Truth Behind Tea's Acidity

The notion that tea contains "tannic acid" is a widespread simplification that science has corrected. While tea is rich in polyphenols—a class of powerful antioxidants—a specific, isolated tannic acid is not the primary component. Instead, these polyphenols, known as tannins in tea, are responsible for the astringent, drying mouthfeel and dark coloration, especially in black teas. The actual acidity of tea comes from a diverse array of other organic compounds, each contributing uniquely to the beverage's final taste profile and health effects.

The Major Acidic Players in Tea

Research has identified a variety of organic acids within the tea plant, Camellia sinensis, which are extracted during the brewing process. The concentration and type of these acids can vary significantly based on the tea variety, processing method, and brewing time.

Quinic Acid: Often found as one of the most dominant organic acids, quinic acid is a major contributor to the tartness in black teas and also plays a role in green tea's flavor. Its presence is influenced by leaf maturity and shading during cultivation.
Malic Acid: Providing a smooth, lingering tartness, malic acid is a key component, especially in black tea. It is also known to enhance fruity flavors and can help mask salty aftertastes in bottled teas. Its content can be affected by the tea's processing.
Citric Acid: This is the familiar sour compound found in citrus fruits. While present in tea leaves, its content is often less than that of quinic or malic acid in un-doctored tea. When adding a slice of lemon, however, the boost in citric acid is what causes black tea to lighten in color.
Oxalic Acid: A well-known organic acid found in various plants, oxalic acid contributes to the sour taste, particularly in black tea. The quantity of oxalic acid can be influenced by processing and even affects the mineral absorption of the tea plant during its growth.
Gallic Acid: Found in black and green tea, this is another type of phenolic acid. It contributes to both the sour and astringent notes of the tea infusion.

The Role of Polyphenols and Tannins

While not typically classified as simple organic acids, the polyphenols within tea—often broadly referred to as tannins—are central to its chemistry and taste. During fermentation, the catechins found abundantly in green tea are oxidized into theaflavins and thearubigins, which are characteristic of black tea. These compounds are what produce the deep, reddish-brown color and the drying astringency that many associate with a strong cup of black tea.

Catechins (EGCG, etc.): These are the primary polyphenols in unfermented green tea, known for their antioxidant effects. They are precursors to theaflavins and thearubigins during the oxidation process for black tea.
Theaflavins and Thearubigins: These are formed during the processing of black tea and are complex polymers of polyphenols. They are potent antioxidants but are also responsible for the color and stronger, more robust flavor profile of black tea compared to green.

Factors Influencing Tea's Acidity

Several factors can influence the final acidic profile of a cup of tea:

Tea Type: The degree of oxidation (fermentation) dramatically alters the tea's composition. Green tea, with minimal oxidation, retains more catechins. Black tea, being fully oxidized, develops more complex polyphenols like theaflavins and thearubigins.
Brewing Time and Temperature: Steeping time and water temperature significantly impact how many of the tea's compounds are extracted. Longer steeping times and hotter water tend to extract more tannins, leading to a more bitter, astringent, and acidic-tasting brew.
Water Chemistry: The mineral content of the water used for brewing can affect the final pH and flavor. Some minerals, like iron, can interact with tannins to create darker colored complexes.

Comparison of Key Tea Acids


Acid	Type	Flavor Profile Contribution	Presence in Tea	Influence
Polyphenols (Tannins)	Phenolic Polymers	Astringent, bitter, dry mouthfeel	All teas, higher in black	Higher extraction with longer steeping
Quinic Acid	Aliphatic Organic Acid	Tartness, prominent note	Black and green tea	Increased by certain cultivation methods
Malic Acid	Aliphatic Organic Acid	Smooth, lingering tartness; enhances fruit flavors	All teas	Varies with processing, higher extraction with heat
Citric Acid	Aliphatic Organic Acid	Sharp, citrusy, tartness; lesser component naturally	All teas; added with lemon	Naturally occurring, more pronounced when citrus is added
Oxalic Acid	Aliphatic Organic Acid	Sour taste, affects mineral absorption	All teas	Content can change during processing stages

Health Implications and How to Moderate Acidity

The acidic components in tea contribute to its many celebrated health benefits, including potent antioxidant and anti-inflammatory effects. However, the tannins can have side effects, particularly for those sensitive to them or with low iron levels. Tannins can bind with non-heme iron (found in plants), reducing its absorption. For individuals with iron deficiency, it is often advised to consume tea between meals rather than with them. Drinking tea on an empty stomach may also lead to nausea in some people, a side effect also attributed to tannins. Adding a splash of milk, which contains protein that binds to the tannins, can also mitigate some of these effects.

Conclusion

In conclusion, the answer to the question "which kind of acid is present in tea?" is a far more complex and interesting story than just "tannic acid." The unique character of every cup of tea—from its color and taste to its health benefits—is a direct result of a dynamic combination of many organic acids and polyphenols. The particular blend depends on the tea variety, how it was processed, and how it is ultimately brewed. A deeper understanding of these compounds not only demystifies your favorite beverage but also enriches your appreciation for its intricate chemistry. For more detailed information on the chemical compounds in tea, consider resources like this review on the topic from the National Institutes of Health: Quality Chemistry, Physiological Functions, and Health Benefits of Organic Acids in Tea.

Frequently Asked Questions

No, "tannic acid" is a commercial term and a specific chemical compound. The tannins found naturally in tea are a broader class of polyphenols that cause the brew's astringent taste but are not technically tannic acid.

The pH of brewed tea is mildly acidic, typically ranging between 5.0 and 6.0. Adding lemon juice or other acidic components will lower this pH further.

Key organic acids found in significant amounts include quinic acid, malic acid, and citric acid, along with others like oxalic acid and gallic acid, which all contribute to the tea's flavor.

Adding acidic lemon juice, which contains citric acid, lowers the tea's pH. This change causes the colored polyphenol compounds to absorb light differently, resulting in a lighter, more orange-yellow color.

For some people, the tannins in tea can cause nausea, especially when consumed on an empty stomach. Adding milk or having food alongside your tea can help mitigate this effect.

Yes, longer steeping times generally lead to a more acidic and astringent brew, as more tannins and other organic acids are extracted from the tea leaves.

Yes, the acidic profile varies depending on the tea's processing. Green tea has more catechins, while oxidized black tea contains higher levels of complex polyphenols like theaflavins and thearubigins.