How to adjust the solution of over-extracted coffee

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When freshly roasted coffee beans are ground into small particles and combined with hot water, a large number of soluble coffee flavor substances are released. These dissolved flavor substances make up the different tastes we drink when we taste coffee.

The over-extracted coffee represents bringing out too much soluble matter in the coffee, and the result of this extraction is a bad flavor.

In a coffee bean, 70% is wood fiber and 30% is soluble matter. About 2% of them are positive flavor substances, and about 10% are bitter and negative substances. Therefore, for a cup of delicious coffee with the right flavor, the best extraction rate is between 18 and 22%.

The dissolution rate and time of different flavor substances in water will be different. Generally speaking, positive substances are the first to be honored, while negative flavor substances take longer to dissolve.

In general, sweet and sour taste molecules are molecular weight compounds, which are more easily extracted by hot water, while bad flavors such as bitterness and miscellaneous taste have a relatively large molecular weight and will be extracted in the middle and later stages.

If you only extract the small molecular weight substances in front, not the high molecular weight substances behind, then the coffee will be sour and sweet, but it will lack taste and show a thin performance. Also because there is no neutralization of bitter substances, coffee will become sharp and sour, which Qianjie Coffee will call inadequate extraction.

If the small molecular weight substance is extracted in front and the high molecular weight substance is released too much behind, then the sweet and sour taste of the coffee will be obscured by the bitter taste, and at the same time it will show a dry feeling and it is difficult to swallow. Qianjie Coffee will call this a situation of overextraction.

From years of experience in brewing coffee in Qianjie, there are two reasons for coffee over-extraction: the high temperature of brewing water and the fine grinding of coffee. The extraction rate of substances in coffee beans with different roasting degrees will also be different.

According to the observation of Qianjie coffee roasting, the shorter the roasting time and the lighter the roasting degree of coffee beans, the lower the density of coffee bean structure after baking, which will also lead to the release of flavor substances in water.

Therefore, when brewing light-medium roasted coffee beans, Qianjie coffee is recommended to use medium grinding / fine granulated sugar size (China 20 standard sieve screening rate of 75-80%), and then with 90-91 degrees Celsius water temperature for extraction.

On the other hand, the medium-deep-roasted coffee beans will burst twice because of the extension of the baking time, so the structure will be relatively loose and the substance will be released more easily in the water.

Therefore, when roasting coffee beans deeply, Qianjie Coffee is recommended to use medium coarse grinding / coarse granulated sugar size (China 20 standard sieve screening rate of 65-70%), and then match the water temperature of 88-89 degrees Celsius for extraction.

In the actual brewing of Qianjie coffee, it is found that with the difference of the variety / treatment method / roasting degree of coffee beans, the extraction rate of some coffee is less than 18%, although it is a bit boring, but the flavor is very clear; the extraction rate of some coffee is 22% higher, although the taste is strong, but it is not dry and astringent. In these cases, Qianjie Coffee is more likely to be described as "low extraction" or "high extraction".