Why does coffee taste sour? Does good coffee taste sour?

Have you ever had sour coffee? Do you think sour coffee tastes weird? For many coffee novices, sour coffee is a bit unacceptable... The taste of coffee and sourness mixed together feels weird.

Friends who often drink single-origin coffee will think of Yirgacheffe beans when they mention sour coffee. Indeed, Yirgacheffe is the representative of acidic coffee. Beginners who have not tried single-origin coffee may wonder, how can coffee be sour? Does sour coffee mean it is expired or inferior coffee? In fact, this acid is not that acid. Coffee contains hundreds of acidic compounds. Today, we will mainly introduce several acids in coffee that affect the taste.

Coffee beans contain acidic organic compounds that can be synthesized by the plant itself and contain weak acid aromas of carbon molecules.

Organic acids include citric acid, malic acid, tartaric acid, acetic acid, chlorogenic acid, and phosphoric acid.

【Citric acid】

Citric acid is an important organic acid. The citric acid in coffee is one of the products of the coffee tree's respiration. The amount of citric acid can be used to determine whether the green beans are fresh. As the coffee cherries mature, the citric acid content will decrease and convert into more sugar. During roasting, citric acid reaches its peak in light roasting and is continuously decomposed and destroyed as the roasting progresses.

【Malic acid】

Malic acid exists in fruits such as apples, hawthorns, and grapes. The concentration of malic acid in green beans is lower than that of citric acid. After roasting, the concentration drops to only 0.1%-0.4% of the weight of the green beans. Malic acid is generally classified as aromatic acid.

【tartaric acid】

Tartaric acid is found in many plants, such as grapes and tamarind. It is one of the main organic acids in wine and one of the sources of astringency in coffee.

【acetic acid】

Acetic acid, also known as acetic acid and glacial acetic acid, is an organic acid. It is a typical fatty acid and the source of sourness and pungent smell in food. In coffee, it mainly comes from the fermentation step in the post-processing process of coffee, so the acetic acid content in washed coffee is generally higher than that in natural coffee in the washed fermentation process. The pressure in the roaster during the roasting process helps to significantly increase the acetic acid content, and helps to maintain volatile acidity and improve the quality of coffee. A small amount of acetic acid gives coffee a winey aroma, but if it is excessive, it will make the coffee taste bitter.

【Chlorogenic acid】

Chlorogenic acid is an acid that is currently prevalent in all green coffee beans, accounting for 6%-8% of the net weight of coffee. Coffee is the plant with the highest chlorogenic acid content among all species in the world. Chlorogenic acid is an important source of the sourness and bitterness of coffee, and has a slight neurostimulating effect on humans. Chlorogenic acid is one of the main acidic substances in coffee. Chlorogenic acid has two isomers, monocaffeic acid that is decomposed during the roasting process and dicaffeic acid that is not decomposed. Among them, dicaffeic acid will make coffee bitter and metallic. During the roasting process, chlorogenic acid will be decomposed into quinic acid and caffeic acid, these two acids will increase the astringency and taste of coffee.

【Phosphoric acid】

Phosphoric acid is an inorganic acid found in high concentrations in Kenyan coffee, giving Kenyan coffee its unique and superior acidity. Phosphoric acid in coffee accounts for only about 1% of the total coffee substance, and is mainly derived from the hydrolysis of phytic acid in the soil. During roasting, the phosphoric acid content increases as the roasting degree continues to deepen. Phosphoric acid increases the brightness and sweetness of coffee.

There are many different acids in coffee, and these are the main ones.

These organic acids will increase or decrease before and after baking.

But this is not the sour taste we experience when we drink coffee. The sour taste we taste mainly comes from the changes caused by the roasting process.

Usually when we roast coffee beans, some components in the coffee beans will undergo chemical reactions to form new acids.

For example: When coffee beans are roasted, chlorogenic acid continues to degrade into quinic acid... and so on~

Medium-light roast - obvious sour taste

Medium roast - moderately sour

Medium dark roast - less acidic

Dark roast - almost no acidity, but strong bitterness

The strength and concentration of each acid are different. The acidity components and proportion of coffee beans are also related to the components contained in the raw coffee beans. The type of coffee beans you choose will also affect the acidity to a certain extent...

Coffee grown at higher altitudes has richer acidic aromas, but lower oil concentration than coffee grown at lower altitudes. These two factors make high-altitude coffee more sour. Written records: Among the eight major production areas in Guatemala, the highest altitudes are about 2,000 meters in Pico Tenango (located in the northwest bordering Mexico) and Huayhanes (located in the southeast bordering El Salvador). The acidity of coffee in these two areas is significantly higher than that in the other six areas, including Antigua.

In addition, the temperature decreases by 0.6 degrees Celsius for every 100-meter increase in altitude. Studies have also found that the sucrose content of coffee beans increases by 10% for every 300-meter increase in altitude. In principle, the higher the acidic aroma and sucrose content, the more fragrant the coffee. This is because the higher the altitude, the lower the temperature and the greater the temperature difference between day and night, which can slow down the growth of coffee and accumulate more nutrients. Sucrose will produce more acidic aromas during the roasting process, which is why the acidity of high-altitude hard beans is far superior to that of lower-altitude soft beans. Altitude, variety, and complex genetic traits and ecosystems all indirectly affect the flavor of coffee.

The acidity of coffee is a lively, bright flavor, similar to the way it is described in wine tasting. If coffee beans lack acidity, they lose their vitality and taste hollow and dull without depth. There are many different characteristics of acidity, such as the acidity characteristics of coffee beans from Yemen, Kenya, Ethiopia, and Yirgacheffe and Sidamo, which have a striking fruity and red wine-like aroma.

And there is another kind of sourness that is sharp and dull, a dead sourness without any aroma. It tastes like vinegar and is hard to swallow.

Caffeic acid is reasonable and even its truly natural state. It is definitely not rotten or smelly.

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