Why does deep-roasted coffee taste sour? What's the difference between deep-roasted and lightly roasted coffee? Where does the sour taste of coffee come from?

Qianjie found that many friends had certain misunderstandings about deep-roasted coffee, such as thinking that deep-roasted coffee was completely acid-free. The cause of the incident was that a friend shared it with Qianjie yesterday. He drank the sour taste from a cup of deep-roasted coffee. Because this was completely different from the theoretical knowledge he had come into contact with, he was very shocked when he drank it sour. He once thought that the beans in the coffee shop were not baked deep enough. "The shallower the coffee is roasted, the more sour it will taste; the deeper the coffee is roasted, the more bitter it will taste." This is a saying that many friends have already heard and heard. It is precisely because of this sentence that most friends have misunderstandings about deep-roasted coffee. This sentence itself is not wrong, but it can easily lead to the misunderstanding that "deep-roasted coffee is completely acid-free." Deep roast coffee has a sour taste, but relatively speaking, it is not so obvious.

Where does the sour taste of coffee come from? The sources of sourness in coffee can be divided into two categories: native organic acids and baking nascent acids. Native organic acids refer to organic acids that already exist when coffee beans are grown, such as chlorogenic acid, citric acid, malic acid... Baking nascent acid refers to the acetic acid (acetic acid) produced by the caramelization reaction of carbohydrates during the baking process.

In an article two days ago, Qianjie mentioned that the organic acids in green coffee beans will gradually decompose and transform during the roasting process. The lighter the roasting, the less organic acids are decomposed and converted. The deeper the roasting, the more they are converted. Organic acids are one of the important sources of sourness in coffee. So this is why the lighter the coffee is roasted, the more sour it is, and the deeper the coffee is roasted, the more bitter it is. Because as the coffee is roasted deeper, the decomposition of organic acids will reduce the acidity. However, this does not mean that deep-roasted coffee is completely acid-free. Because organic acids are not completely decomposed, even after the coffee is roasted to the second burst, a small amount of organic acids will still exist in the coffee to contribute to the sourness. At the same time, not all the sourness in coffee is provided by organic acids! During baking, carbohydrates will be converted into acetic acid through caramelization reaction, and acetic acid will gradually increase as the degree of baking deepens.

So we can know that the acids in coffee will not disappear as the roasting deepens, but their proportion in coffee becomes less. But under normal circumstances, we can't drink obvious sourness from deep-roasted coffee, because the acid in deep-roasted coffee will be covered up by "blind tricks"!

Why is the sourness of deep-roasted coffee so difficult to detect? Under deep roasting, the coffee will have a strong bitterness brought by carbonized substances and caramelization products. Compared with acid, we are more sensitive to the perception of bitterness. Moreover, the amount of bitter substances is not small, so the trace sourness of coffee is concealed. In addition, the coffee has signature aromas such as smoke and chocolate after deep roasting. Because aroma dominates the sense of smell and gives priority to us to associate it, it further weakens the perception of sourness.

To sum up, we can see why it is difficult for us to drink obvious sourness from deep-roasted coffee. Not only because the sourness itself is less, but also because the sourness is covered up by the bitterness and aroma of deep-roasted coffee.

Why can some people drink sour taste from deep-roasted coffee? If you feel acid in deep-roasted coffee, it may be caused by these conditions. One is that this coffee itself belongs to a coffee with relatively rich "acid content", so even after deep roasting, it still retains detectable acid; or it is because this cup of coffee has insufficient extraction. The dissolved substances are not enough to completely cover up the sour taste, so this gives you a chance to capture the sour taste of the coffee.

Of course, it may also be because your senses are more sensitive and you can capture even the subtle sour taste ~

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