Where Does Coffee Acidity Come From?

Acidity in light roast coffee comes from organic acids already present in the green coffee bean. During high-temperature roasting many of these acids break down or volatilize, so light to medium roasts retain more of them. The main leftovers are chlorogenic acid, quinic acid, citric acid, malic acid, phosphoric acid, acetic acid, and lactic acid.

Chlorogenic acid is not water soluble, so it reads as astringency rather than sourness, while quinic acid, formed as chlorogenic acid degrades, tastes bitter. The SCA cupping form treats acidity as a sensory impression shaped by sweetness and other perceptions together, which is why the same coffee can seem apple-like or sharp depending on the taster and the brew.

Many people, when they first try a light-roast pour-over, are caught off guard by that bright acidity. Some find it refreshing like fruit juice, while others find it sharp and hard to bear. Where exactly does the acidity in coffee come from? Why is some acidity pleasant while some makes us frown? This article starts with the organic acid composition of green coffee beans and, combined with the SCA cupping definition of acidity, helps you clarify the sources of acidity and the criteria for judging it. At the same time, we have selected four light-roast single-origin beans with distinct styles, including Front Street Coffee Fruit Dingding and Front Street Coffee Little Tomato. They have vivid fruity aromas and balanced sweet-tart flavors, making them very suitable for friends who are just starting to explore light-roast pour-over.

The acidity in coffee can be the finishing touch, or it can ruin the entire cup. When we drink coffee normally, how should we distinguish whether that acidity on the palate is pleasing or unpleasant?

Where does the acidity in coffee come from?

Green coffee beans naturally contain a variety of organic acids, but during high-temperature roasting, many acids gradually decompose or volatilize. Therefore, in beans roasted light to medium, the organic acids that remain are mainly chlorogenic acid, quinic acid, citric acid, malic acid, phosphoric acid, acetic acid, and lactic acid.

Among them, chlorogenic acid is not soluble in water, so the taste buds actually cannot taste its acidity; instead, it mainly creates astringency on the surface of the tongue. Quinic acid is the product of chlorogenic acid degradation during roasting. It is non-volatile and tastes bitter.

So why can we still taste acidity in coffee that resembles apples or Yakult?

By comparing with the latest SCA cupping form's definition of acidity, we can find that the reason we can perceive acids other than citric acid is more because the acidity in the brewed coffee stimulates the sensory organs, which in turn triggers related surrounding sensory associations.

In other words, the judgment of acidity is not determined solely by acidity level, but is a comprehensive association the senses make with food after receiving different degrees of acidity, sweetness, and other perceptions. For example, when we perceive an apple-like acidity, it is often because the fresh sweetness is more prominent than the acidity, so the impression of apple juice—fresh, sweet, and slightly tart—comes to mind.

It should be noted that high-quality light-roast coffee is by no means simply sour; rather, it has sweetness within the acidity and very low bitterness. Therefore, it is recommended to prioritize beans with obvious fruit flavors, as this makes it easier to brew the elegant aroma of light-roast coffee. The following four are all light-roasted and very friendly to beginners:

1. Floral and fruity acidity—Front Street Coffee Fruit Dingding Coffee Beans

Country: Ethiopia

Region: Yirgacheffe

Variety: Ethiopian heirloom

Altitude: 2,300 meters

Processing method: Washed

Flavor: Bright fruity aroma, with flavors of citrus, blueberry, honey, and green tea, with prominent acidity

2. Juicy sweet and sour—Front Street Coffee Little Tomato Coffee Beans

Country: Kenya

Region: Thika

Processing station: Asali Honey Processing Station

Altitude: 1,550–1,750 meters

Variety: SL28 and SL34

Processing method: K72 washed

Flavor: Cherry tomato, smoked plum, snow pear, brown sugar, plum

3. Berry and citrus—Front Street Coffee Huakui Coffee Beans

Country: Ethiopia

Region: Guji Hambela

Altitude: 2,300 meters

Processing method: Natural

Variety: Ethiopian heirloom

Flavor: Cream strawberry, citrus, light floral aroma, berries, black tea

The above content is compiled by CoffeeHunters, a coffee news website.