Acidity is the bright, dry sensation that enlivens the taste of coffee.
Many coffee drinkers have a negative association with coffee acidity. Too acidic coffee can be soury and have unpleasant, edgy bodily sensations. Others may experience digestive issues from too acidic coffee. For this reason, many seek out “low acid” coffees or experiment with brew methods that decrease acidity. Many have discovered that darker roast coffee has less acidity than lighter roast coffee. But to coffee professionals, acidity is an important indicator of coffee quality.
Average pH in coffee is 5, (neutral is 7). Vinegar is 3 and lemon is 2 for comparison. However, perceived acidity and pH do not always correlate. A coffee’s perceived acidity is a factor of roast degree and the type of acidity combined with the brewing method.
When coffee professionals are evaluating coffee there are a number of factors they must consider. Is it clean? Is there no ferment or mold? Is it free of defects? Is it uniform? Is it fresh? To evaluate coffee for cup quality one of the important elements is a coffee’s acidity. Coffee acidity is a reflection on crop quality. Historically, acidity was evaluated on a pass/fail basis. Good acidity indicates that the coffee was grown and processed correctly. It indicates the the coffee is fresh and free from defects that may mar it’s flavor.
Coffee professionals use an evaluative method called cupping. Samples of coffee are roasted to a specific light roast, a trade roast, that emphasizes the acidity in a sample. Trade roasts are meant to amplify any defects a coffee may have, they do not reflect the flavor a coffee may have in production roasts. It is an evaluative tool. Once a coffee passes this evaluation it is profiled to determine its best roast for production. Here a coffee is evaluated for its ideal flavor balance.
Ideally, a good coffee will display a sweet, tart, citric acidity resembling fresh lemon. This indicates that the coffee is fresh, clean and well prepared. Coffee that display good citric acidity are from arabica coffee trees, grown at elevation under a canopy of shade, and are wet processed in a timely manner. This type of acidity presents a pleasant lively sensation to the coffee. Without it, coffee tastes bland and flavor is muted.
There are a number of other acids that contribute to coffee’s flavor, for better or worse. The presence of these acids in excess is due to issues relating to coffee’s growing, production, roasting and brewing. Other acids in coffee include:
- chlorogenic acid – from growing, part of the plant’s defense. High stressed and Robusta coffee trees will display excess. Has a harsh, bitter character.
- malic acid – from growing. Typical in full sun grown coffee. Due to the plant’s respiration from hot daytime temperatures to colder night time temperatures. Has a lingering apple skin character.
- acetic acid – from processing, too long in fermentation tank or temperature too high in tank. Has an unpleasant vinegary character.
- quinic & caffetic acid – from roasting and brewing. It is the breakdown of chlorogenic acid resulting from too much time heat is applied to organic compounds. Too slow roasting or brewing. Has an unpleasant quinine character like tonic water.
- buteric acid – from production. Indicates ferment in the coffee bean. Has a rank sweetness resembling watermelon rind.
The prevalence of light roast coffees among many new roasting firms has led to a change in attitude regarding acidity in recent years. Since acidity dominates the flavor in light roasts, acidity is flavor for these firms. This has led to an opinion that all acidity is good, regardless of its source. Coffees in the past that would have been rejected are now often celebrated for their unique flavor. For some, light roast itself is a marker of quality, based on the mistaken notion that if acidity is flavor, more acidity is more flavor. However, one should not confuse roast degree with coffee quality.
Generally speaking, acidity decreases in roasting. Darker roast coffees will display less forward acidity than lighter roasts. Low grown coffees break down more easily than denser, high grown coffee so are not suitable for darker roast.
At Kaladi, we believe that good acidity represents one important element to the overall balance in flavor but it should not dominate or ruin the experience in coffee. We select only shade-grown arabica coffee that have been wet processed. We roast each coffee to a specific temperature that brings out the best balance of flavor. Additionally, Air-Roasters have more efficient heat transference that drives off the moisture in green coffee rapidly, reducing soury tasting acids.