Why does coffee taste sour? How do you know if the sour taste in coffee beans is good or bad?

Professional coffee knowledge exchange more coffee bean information please follow the coffee workshop (Wechat official account cafe_style)

For more boutique coffee beans, please add private Qianjie coffee on Wechat. WeChat account: qjcoffeex

Some friends think that the sour taste in coffee is a negative taste and a sign that the coffee is not good / fresh.

Some friends believe that sour coffee is the performance of good quality coffee, because it can drink flowers, fruits and various sugars to give off an upward flavor.

The sour taste in coffee can be a plus item or a minus item. In daily life, how can we tell whether the sour taste of coffee is good or bad?

Why is the coffee sour?

Raw coffee beans are rich in organic acids, but many acids will gradually decompose / disappear after baking at high temperature. Therefore, only chlorogenic acid, quinic acid, citric acid, malic acid, phosphoric acid, acetic acid and lactic acid remain in the roasted coffee beans.

Chlorogenic acid does not dissolve in water, so the taste buds can not taste sour, it will only give the tongue a rough feeling. Quinic acid is formed by baking and degradation of chlorogenic acid, which is non-volatile and bitter.

"so the sour taste of coffee is determined by citric acid, malic acid, phosphoric acid, acetic acid and lactic acid?"

If put in the past, the answer of Qianjie may be "yes". However, a recent study pointed out that taste buds can only recognize citric acid in coffee liquid and have a chance to identify phosphoric acid.

The acid that can be tasted in coffee liquid does not come entirely from the dissolution of organic acids. In a recent study on the sensory threshold of organic acids in coffee, which was conducted by CoffeeMind and researchers at the University of Southern Denmark, it was suggested that when people drink certain organic acids in coffee, they may not find effective neurological evidence in coffee to stimulate the substance.

The researchers roasted coffee beans in Kenya, Bolivia and Brazil, and then recorded the concentration of various organic acids in the coffee liquid (green) in a cup test. and compared with the sensory threshold (orange) needed by the human body to recognize various organic acids.

It can be seen that in addition to citric acid (Citric) and phosphoric acid (Phosphoric), other acetic acid (Acetic), lactic acid (Lectic), malic acid (Malic) actually exist in the coffee solution concentration, the taste buds can not feel.

What do you mean? For example, the malic acid you feel does not come from the malic acid in the coffee. The taste of Toledo is not caused by the soluble lactic acid taste in the coffee.

Then why can we feel the coffee

Sour taste like apple, Yoledo and so on?

According to the definition of the sour taste of coffee in the latest SCA cup meter, we can see that we can drink the sour taste other than citric acid, which is more likely to stimulate the taste perception organs of brewed coffee, which leads to the peripheral perception combination.

In other words, the perception of sour taste is not judged by acid alone, but by the senses to associate food with different degrees of sour and sweet / other perceptions. We can feel the sour taste of the apple, maybe the sweet feeling is more obvious than the sour feeling, so we think of the sweet and sour apple juice.

So how do we judge the sour coffee? In the old SCA cup meter, acid was independent. But in fact, the judgment of sour taste needs to be combined with other senses, and it is impossible to better judge whether the sour coffee in the cup is good or bad.

So in the latest cup meter, SCA puts "acid" into the boundaries of other senses, constructs the feeling of sour in terms of taste and other senses, and provides two ways to describe and distinguish it: "dry sour" and "sweet sour".

The bad "dry sour taste" refers to the sour taste of herbs (usually caused by the poor quality of the coffee beans themselves and not fully ripe); the sour taste of chewing grass (usually caused by the coffee beans roasting without penetrating / the quality of the coffee beans / their own quality); wine-like sour taste (usually caused by the coffee beans are not roasted too lightly / not roasted thoroughly).

A good "sweet sour / sweet / sour taste" refers to acidity with a sense of juice, fruit and brightness. Coffee can show these sour tastes. Coffee trees are usually planted at high altitudes (more than 1200m) and the fruit is not harvested until it is ripe (high in sugar).