I have met many people who, when describing their coffee preferences, would mention "I don't like sour coffee". In fact, when I first came into contact with specialty coffee, I was also surprised by the acidity of some coffees, because it was completely different from the impression of "bitter coffee". Although sharp acidity may indeed make people unhappy, after drinking more coffee, I found that coffee lacking acidity really lacks a little color, a little depth, and a little balance. So why is coffee sour? How to appreciate this acid?
Acidity is one of the normal flavors of coffee. It can also be said that the taste of coffee has a sour side. It's just that before the popularity of single-origin coffee, Italian milk coffee and three-in-one instant coffee were popular, and the sourness was suppressed or masked by extremely deep roasting and other additives, so the coffee we are familiar with is mainly "bitter coffee".
Coffee contains more than 30 kinds of acidic substances, which also makes the overall pH of coffee acidic. Although these acidic substances are not equivalent to the sourness of coffee we are talking about, they are the source of sourness. The amount of acidic substances in coffee beans depends on the coffee variety and the climatic conditions of its origin. For example, coffee beans from high-altitude and low-temperature areas have more acidic substances and richer flavors.
These acidic substances can be roughly divided into two categories: chlorogenic acid and organic acids (citric acid, malic acid, tartaric acid, lactic acid, etc.), which constitute the main source of coffee sourness. Among them, organic acids give coffee different flavor characteristics. For example, malic acid tastes similar to fresh green apples, citric acid brings citrus flavors, and tartaric acid has a grape flavor.
Chlorogenic acid will gradually decompose during the roasting process of coffee beans to produce quinic acid. Quinic acid has an unpleasant bitter and sour taste. Therefore, as the roasting depth deepens, chlorogenic acid gradually decreases, the acidity of coffee gradually decreases, and the bitterness gradually increases. Therefore, lightly roasted coffee is more sour, and deeply roasted coffee is more bitter.
In addition to the variety, origin and degree of roasting, the processing method of the raw beans, the brewing method, the extraction time, the water temperature and the degree of grinding will all affect the strength of the coffee's acidity. For example, generally speaking, washed coffee beans are more acidic than sun-dried beans, and coarsely ground coffee powder is more acidic than finer ones.
The strength of the coffee's acidity itself cannot tell us whether the coffee is good or bad, because some sourness is pleasant, while others are disgusting. In other words, "acidity" itself can also be good or bad, just like the acidity of aged vinegar and the acidity of oranges, which give different feelings to the tasters. Bright, soft and lively fruit acid with the scent of ripe berries is loved by people, while single, sharp, irritating, and even astringent and smelly acid is naturally not what we expect.
Just like the role of vinegar in food seasoning, appropriate acidity can bring layering, depth, clarity and richness to the flavor, making the taste more refreshing and lively. In fact, it is more important not to abandon it, but to find a balance between sour, bitter, sweet and fragrant, so that the acid can play a role without being so dry that people "feel sour".
