What Kind of Acid Is in Coffee?

October 23, 2025 •

4 min read

With an average pH ranging between 4.85 and 5.10, most coffees are considered slightly acidic. The source of this acidity is a complex blend of acids naturally present in the beans, but understanding what kind of acid is in coffee involves looking at how processing and roasting change its chemical composition.

Quick Summary

Coffee's acidity comes from several organic and chlorogenic acids in the beans. Roasting breaks down initial acids like chlorogenic, creating new ones such as quinic and acetic, which dramatically alters the final taste profile.

Key Points

Acids Vary by Roast: Light roasts are higher in fruity citric and malic acids, while dark roasts produce more bitter quinic and acetic acids through thermal breakdown.
Chlorogenic Acids are Key: Abundant in green beans, chlorogenic acids degrade during roasting to form other compounds that influence the final flavor.
Altitude Affects Flavor: Beans grown at higher altitudes often have brighter acidity due to higher levels of acids like citric.
Cold Brew Lowers Acidity: The extended, low-temperature steeping of cold brew extracts fewer acidic compounds, resulting in a smoother, less acidic taste.
Choose Robusta for Lower Acidity: Robusta beans typically contain lower levels of acidic compounds than Arabica, making them a naturally less acidic choice.
Acids Affect Digestion: The acidity in coffee can aggravate conditions like acid reflux or IBS in some individuals, but many find it beneficial for digestion.

The Primary Acids Found in Coffee

Coffee's acidity is not from a single compound but from a dynamic cocktail of acids that evolve throughout its journey from a green bean to a brewed cup. These can be broadly divided into organic acids and chlorogenic acids (CGAs), which change drastically during roasting.

Chlorogenic Acids (CGAs)

Chlorogenic acids are the most abundant type of acid found in raw, green coffee beans, making up a significant portion of their dry weight. This category is not a single compound but a group of polyphenol antioxidants that are critical for the coffee plant. They are the primary source of acidity in lighter roasts and contribute a clean, crisp character. The heat of roasting, however, causes a major chemical reaction where these CGAs break down into other compounds, most notably quinic and caffeic acids, altering the flavor profile significantly.

Organic Acids

Several other organic acids are also naturally present in the coffee bean, contributing a variety of fruity and complex flavors. Their levels also shift during roasting.

Citric Acid: The same acid found in lemons, limes, and oranges, citric acid contributes a bright, citrusy acidity, especially in coffees grown at higher altitudes. It is most prevalent in Arabica beans and light roasts, decreasing as the roast darkens.
Malic Acid: This acid provides a softer, fruit-like tartness reminiscent of green apples, peaches, or plums. Like citric acid, malic acid concentrations are highest in lighter roasts and diminish with longer roasting times.
Acetic Acid: A component of vinegar, acetic acid can add a mild, sharp tang in small amounts. At higher concentrations, it can produce an unpleasant, overly sour or vinegary taste, which may indicate improper processing. It develops during the roasting process as carbohydrates break down.
Phosphoric Acid: An uncommon but highly sought-after acid, phosphoric acid can contribute a vibrant, almost effervescent quality to the acidity, often compared to sparkling water. It is a signature characteristic of some specialty coffees, particularly those from Kenya.
Quinic Acid: This acid increases as chlorogenic acids break down during roasting, especially in darker roasts. It is primarily responsible for the bitterness and astringency of dark-roasted and stale coffee, rather than a pleasant, fruity acidity.

How Roasting and Processing Affect Acidity

Roasting is a powerful factor in determining the final acidic profile of a coffee. As the beans are heated, chemical reactions transform the acids, influencing both the perceived flavor and the overall pH.

Roast Level: Lighter roasts retain more of the delicate, original organic acids like citric and malic, resulting in a brighter, fruitier cup with higher perceived acidity. As the roast darkens, these heat-sensitive acids degrade, while more quinic and acetic acids are produced. This results in a bolder, more bitter flavor and a lower-perceived acidity, even though the actual pH may not change dramatically.
Processing Method: How coffee beans are processed after harvesting also impacts their acid content. Wet-processed (washed) coffees typically have a cleaner, brighter, and higher acidic profile, as the process removes fruit pulp before drying. In contrast, natural or dry-processed coffees, where the fruit remains on the bean during drying, can have a lower acidity and a fruitier flavor.

Comparison of Roast Levels and Their Acids


Characteristic	Light Roast	Dark Roast
Dominant Acids	Chlorogenic, Citric, Malic	Quinic, Acetic
Perceived Flavor	Bright, fruity, floral, more nuanced	Bold, bittersweet, chocolatey, smoky
Acidity Level	Higher perceived acidity	Lower perceived acidity
Body	Lighter, thinner body	Heavier, fuller body
Bean Appearance	Light brown	Dark brown or nearly black, oily

Reducing Coffee Acidity for a Smoother Cup

For those who experience stomach discomfort, acid reflux, or simply prefer a less vibrant cup, adjusting brewing and preparation can significantly reduce the perceived acidity.

Brewing Method

Cold Brew: The prolonged, low-temperature steeping process of cold brewing extracts far fewer of the acidic compounds from the coffee grounds. This results in a remarkably smooth, sweet, and low-acid concentrate.
French Press: The full immersion brewing of a French press, combined with using a coarse grind, also results in a coffee with a lower perceived acidity compared to drip methods.

Grind and Time

Coarser Grind: A coarser grind exposes less surface area of the coffee grounds to water, slowing down extraction and releasing fewer acidic compounds.
Longer Brew Time: For hot brewing methods, a slightly longer extraction time can help balance the acidity, though over-extraction can lead to bitterness.

Other Options

Additives: Adding milk, cream, or a pinch of baking soda can neutralize some of the acidity in a finished cup due to their alkaline properties.
Low-Acid Beans: Selecting coffee beans from lower-altitude regions, such as Brazil, Sumatra, or Bali, can provide a naturally less acidic option.
Decaf Coffee: Decaffeination processes remove some phenolic acids, resulting in a slightly less acidic final product. Caffeine itself can also stimulate stomach acid production, so a decaf option can be gentler on sensitive stomachs.

Conclusion

Coffee's complex and layered flavor is largely thanks to the variety of acids within the bean. From the fruity, bright notes of chlorogenic and citric acids in a light roast to the bitter, astringent quinic and acetic acids of a darker one, each acid plays a unique role. Understanding these different acids empowers coffee drinkers to make informed choices about their beans and brewing methods. By manipulating factors like roast level, bean type, and preparation, you can enjoy a coffee tailored to your specific taste preferences and digestive needs.

For more insight into the science behind your daily brew, consider reading research from the Coffee and Health organization. https://www.coffeeandhealth.org/

Frequently Asked Questions

Light-roasted coffee made from high-altitude Arabica beans generally has the highest perceived acidity, as the roasting process preserves more of the natural citric and malic acids.

Yes, you can reduce coffee acidity at home by choosing a dark roast, using a coarser grind, brewing with cooler water (like in a cold brew), or adding milk or a pinch of baking soda.

Acidity refers to the actual pH level, while acidic taste describes the bright, crisp, or tangy flavor notes that result from the coffee's various acids. A coffee can have a low pH but still be perceived as balanced or smooth.

Dark roasts are often perceived as less acidic because the roasting process breaks down the more delicate acids, like citric and malic. However, this process also creates bitter quinic and acetic acids, changing the flavor profile rather than necessarily lowering the overall pH dramatically.

Yes, cold brew is significantly less acidic than hot-brewed coffee, often by as much as 67-70%. The cold water brewing process extracts fewer of the acidic compounds from the grounds.

Chlorogenic acids (CGAs) are the most abundant acids in green coffee and powerful antioxidants. During roasting, they break down into other compounds like quinic and caffeic acids, which contribute to bitterness and astringency.

Robusta beans are naturally less acidic than Arabica beans. This makes Robusta coffee a good choice for those seeking a lower-acid option with a smoother, earthier flavor.