Coffee is over-extracted, what is the reason for insufficient extraction? what does over-extraction mean?
To define whether a cup of coffee is good or not, perhaps everyone has different taste requirements. Some people like the fragrance of flowers, some prefer fruit rhyme, while others prefer black nut notes. But most people can agree on the taste they don't like, such as dry sour taste, charred bitterness, mixed wood taste and so on.
In the category of hand-brewed boutique coffee, a cup of coffee usually has three states: insufficient extraction, over-extraction and ideal extraction.
If you drink coffee with moderate concentration, full flavor and comfortable taste, people still want to drink it. Even if it is not measured by professional equipment, it is known that its extraction rate falls within the appropriate range (not necessarily the gold cup standard). When a cup of coffee obviously has a negative taste and tastes objectionable, it means that the extraction is probably not done properly. At this time, people usually use "over-extraction" or "insufficient extraction" to describe it.
When brewing a pot of coffee, there are many factors that affect the extraction of flavor substances, such as grinding degree, water temperature, time, ratio of powder to water, stirring method and so on. All the means to improve the extraction rate may be the cause of over-extraction. similarly, the direction of reducing the extraction rate often leads to insufficient extraction of coffee. Then, the premise of adjusting a reasonable brewing plan is to correctly judge the extraction state of coffee.
The release order of flavor substances in coffee during extraction is as follows: sour-sweet-bitter. When most of the coffee powder particles are not fully extracted, it means that only a small amount of soluble matter is brought out by water, and the acidity of the front section will be released first. due to the lack of sweetness and mellow bitter support, the coffee tastes faint in the first place. with abrupt acid, not only the taste is relatively thin, but also no aftertaste to speak of.
When the extraction rate of some particles is too high, it means that water brings out too much soluble matter in coffee, and most of these late released macromolecules are bitter and mixed flavor. In the description of the coffee flavor in the superb state, the entrance is a bitter, woody taste that is hard to swallow, and the tongue sometimes has a sense of convergence, that is, astringent.
There are many reasons for insufficient extraction, such as too rough grinding degree, too low water temperature, too large ratio of powder to water, low intensity of water injection, and too short contact time between powder and water. On the contrary, the reasons for the over-extraction state of coffee are divided into various brewing parameters: too high water temperature, too fine grinding, too much water injection, too long extraction time, too strong water injection stirring, and so on.
In fact, in our daily cooking, there is rarely a simple lack of extraction or excessive extraction. Under the premise of stable parameters, the most likely to occur is the uneven extraction, that is, part of the coffee powder is over-extracted, while the other part is insufficient, so that the flavor performance is mixed with the defects of both, that is, salty acid and bitter, which is difficult to distinguish.
In judging the extraction state, Qianjie thought that it should not only rely on the taste index, but also analyze the flavor type of coffee beans and the whole extraction framework.
For example, when brewing light-roasted sour coffee for less than 2 minutes, the coffee taste is light and sour, obviously in a state of insufficient extraction, we can start from fine grinding particles and slightly slow down the pace of water injection to see if it can be improved.
When the time is all right, the taste is empty and boring, the coffee is neither bitter nor sour, and most of the powder beds are overstocked at the bottom, probably because some macromolecular mellow substances in the coffee are also released in large quantities, masking the light flower and fruit flavor. At this time, the method of water injection can be adjusted appropriately, and the powder bed can be raised as much as possible after steaming, so that the sour and sweet substances have more space to release.
If the coffee is not finished in 2 minutes and 20 seconds, the entrance is an unusual bitter rhyme, mixed with a hint of straw wood, which can not be dispersed at the root of the tongue for a long time, the coffee is very likely to be over-extracted. When eliminating the causes, we might as well adjust the degree of grinding, increase the intensity of water flow, and replace the filter cup with fast flow rate.
If no matter shallow baked beans or deep baked beans, the coffee always has a strong sour or bitter feeling, and the tail rhyme is dry, the surface of the powder pit is sticky and muddy, and it takes a long time to drip, which is probably caused by too much fine powder. It is recommended to screen out some fine powder to avoid clogging and soaking the coffee for too long.
Front Street Cafe
No. 10 Baoqian street, Yandun road, Dongshankou, Yuexiu district, Guangzhou, Guangdong province
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