Cold brew has become a staple in cafés and kitchens alike. If you've ever wondered why cold brew tastes so different from its hot-brewed counterpart—especially when it comes to acidity—you're not alone. Acidity can be a misunderstood concept in specialty coffee - many people associate it with sourness, or even bitterness, and worry that it is elevated in cold brew. In reality, acidity is what gives a cup of coffee its brightness, vibrancy, and complexity, bringing forward especially fruit notes. In this article we will explore acidity in coffee, especially in cold brew, and how it's rooted in chemistry, sensory perception, and extraction theory.
Understanding Coffee Acidity: It's More Than Just pH
In everyday conversation, acidity is often reduced to a number on the pH scale. But in coffee, that number tells only part of the story. The true experience of acidity in a cup has less to do with how acidic the liquid is chemically, and more to do with how that acidity is perceived by the palate. Scientists and coffee professionals have found that titratable acidity (TA) is a much better predictor of how acidic coffee tastes than pH alone. TA measures the total concentration of acids in the coffee and reflects how much base is needed to neutralize those acids, offering a more comprehensive picture of the coffee's sourness and brightness.
To understand this better, imagine tasting two cups of coffee that both have a pH of 5.0. One may taste flat and dull, while the other may come across as vibrant and juicy. That’s the difference titratable acidity makes. While pH measures the concentration of hydrogen ions and tells us how acidic a solution is chemically, titratable acidity represents the buffering capacity—how strongly the coffee resists changes in pH when interacting with other substances like milk or saliva. In sensory terms, TA correlates more closely with the kind of tartness or zing we actually perceive when we drink coffee.
Coffee naturally contains a wide range of organic acids that develop during growth, fermentation, drying, and roasting. Some of these acids are intrinsic to the green coffee bean, while others are formed or transformed during roasting. The most notable include citric acid (which gives a citrus-like brightness), malic acid (associated with green apples), acetic acid (sharp and vinegary in excess), lactic acid (smooth and creamy), quinic acid (which can taste astringent or medicinal if over-extracted), and chlorogenic acids (which break down during roasting into other flavor-active compounds). The concentration and balance of these acids determine much of what we taste in the cup.
Interestingly, not all acids are perceived equally. Citric and malic acids, for instance, tend to be perceived as pleasant, crisp, and refreshing, especially when balanced with adequate sweetness. Acetic acid, on the other hand, can quickly become unpleasant if it dominates. Lactic acid often contributes a subtle roundness, especially in anaerobically processed coffees. Quinic acid, which increases with darker roasting, contributes to bitterness and can make coffee feel sharp or medicinal if not well managed. This is why roast level and processing method play such an important role in a coffee’s acidity profile.
Perception is also influenced by aroma. Our brains interpret flavor through a combination of taste and smell, and fruity, floral aromas can amplify the perception of acidity. A coffee that smells like lemon, berries, or wine is more likely to be interpreted as bright and acidic—even if its actual acid concentration is lower than a coffee with a more muted aroma. Conversely, aromas associated with caramel, nuts, or chocolate tend to round out acidity and make it feel softer or more integrated.
The final impression of acidity depends on context and balance. Acidity that’s balanced by sweetness and body can feel lively and refreshing. Acidity without sweetness, however, can taste sour, sharp, or even metallic. This is why acidity is not judged in isolation by professional tasters. Instead, they consider its intensity, quality, and how well it integrates with other elements of the cup. A well-balanced coffee might have high acidity but still feel smooth and satisfying because it also delivers sweetness and a pleasant mouthfeel.
Why Cold Brew Coffee Tastes Less Acidic Than Hot Brew
One of the most defining features of cold brew coffee is its smooth mouthfeel. Compared to hot coffee, cold brew is often described as mellow, round, and low in acidity. But this difference is not merely a result of perception or preference—it stems from fundamental differences in the chemistry of extraction.
When hot water is used to brew coffee, it acts as a powerful solvent. At higher temperatures, water can extract a broader and more complex range of compounds, including volatile aromatic molecules and organic acids. Many of the acids responsible for brightness and vibrancy in coffee—citric, malic, acetic—are more soluble in hot water and are released quickly during the brewing process. This results in a cup that carries distinct fruit, citrus, and wine-like notes, especially when brewed correctly with light to medium roasted beans.
Cold brew, on the other hand, uses water typically between 4°C and 20°C. These lower temperatures slow down the movement of molecules and reduce the solubility of certain compounds. Even though cold brew is steeped for a much longer period—often 12 to 24 hours—it still fails to extract the same amount or spectrum of organic acids as hot brew. As a result, the final beverage contains fewer of the bright acids that give coffee its characteristic zing. This leads to a cup that is lower in perceived acidity, and softer on the palate.
Interestingly, the actual pH difference between cold brew and hot brew is minimal. Both might register a pH of around 5.0, which is mildly acidic. However, cold brew has consistently been shown to have lower titratable acidity (TA)—a better measure of how acidic a drink tastes to us. TA reflects the total amount of acids present, not just how strong they are, and it better correlates with our sensory experience. So while cold brew may be just as acidic in pH, it has fewer total acids contributing to the flavor profile, and this results in a smoother, rounder taste.
Moreover, many of the acids that do end up in cold brew are the less volatile or more stable ones—like chlorogenic acids and some quinic acids—that tend to produce deeper, earthy flavors rather than fruity or floral ones. This is part of the reason extraction time is so important when brewing coffee cold, to ensure these acids can still create this important part of the flavour profile and contribute vibrancy.
In addition to the chemical composition, temperature itself affects how we perceive taste. Colder beverages tend to dull our sensitivity to acidity and bitterness. This sensory suppression further reduces the perceived brightness of cold brew. Even if a cold brew contains a modest level of citric or malic acid, the cool temperature mutes the taste receptors that would normally pick up on those flavors. This is one of the reasons cold brew is so often enjoyed black, without the need for sugar or milk: its mellow profile is inherently easy to drink.
Overall, cold brew's lower acidity is a combination of lower extraction efficiency for bright acids, the suppression of flavor perception at cooler temperatures, and a tendency to extract aromatics that lean toward sweetness, bitterness, and body rather than pungency or zest. These characteristics make cold brew the ideal beverage for those seeking a smoother cup or requiring a lower-acid option for dietary reasons. However, they also mean that capturing complex acids in cold brew requires a more thoughtful approach to brewing. Our Ethiopia 231 and Colombia 170 are great examples of a flavor profile that is perceived as higher in acidity without compromising the quality of obvious fruit notes like strawberry and melon, while being balanced by a pleasant sweetness.
