Coffee powder too much hand-brewed coffee solution to brew coffee has appeared bitter taste how to do?

I believe that many friends who brew coffee will face the trouble of over-extraction. Many times we can avoid this situation by adjusting parameters or techniques, but sometimes because of coffee equipment can not be adjusted, so we can only silently endure, when a master.

First to explain what is "over-extraction", in the coffee extraction theory, coffee beans soluble in water substances accounted for about 30%, but not all soluble substances are what we think good taste, so over-extraction generally refers to the dissolution of excessive flavor substances in coffee powder, rushed out of the coffee has unpleasant bitter taste, bitter taste.

It is easier to over-extract the situation is that the grinding quality caused by insufficient performance of the bean grinder is not good, and there are more coffee fines, resulting in over-extraction and bitter taste. Perhaps we should change our thinking and use some kind of "intervention" to reduce the extraction rate of coffee. Is it feasible? The use of variable temperature extraction may be a good choice, Qianjie previously introduced a step-by-step cooling extraction method from high to low water temperature, characterized by a relatively high sweetness of coffee, rich flavor. This method is mainly to reduce the extraction rate in the middle and later stages and avoid bitterness in coffee. However, what Qianjie introduced to you today is the use of low-temperature water injection in the steaming stage. Emi, winner of the 2018 WBrC, also uses a low-temperature steam-extraction method. However, her brewing was somewhat special. She used a filter cup with a valve to extract each other by soaking and dripping. Emi's water injection scheme is mainly divided into three stages. The first stage is to close the valve and soak it in 80 ° C hot water. The second stage is to open the valve and extract it with 95 ° C hot water. The third stage is to close the valve and soak it with 80 ° C hot water. Finally, open the valve and filter the coffee solution.

Emi explained that the reason for using low temperature steaming is to gently extract the sweetness of coffee while avoiding the dry tail of coffee. In the front street view, this is actually also a measure to reduce the extraction rate, low temperature with soaking, on the one hand to avoid water early escape caused by insufficient coffee extraction, on the other hand, low temperature also makes coffee bitter substances more difficult to release. If it's because coffee is more finely ground, can you use this method to avoid bitterness? This test is Ethiopia's Huakui coffee beans, front street using a hand mill (300 yuan gear) for grinding, in the adoption of No.20 sieve screening rate of 80% grinding degree, using front street standard brewing parameters, total extraction time of 2 minutes and 33 seconds. The extraction time is slightly longer because the powder diameter distribution is relatively dispersed, and the proportion of fine powder is large (the fine powder rate measured by the powder sieve is 14%), so the water speed is relatively slow. Coffee presents balanced berry notes, black tea notes and lingering dry bitterness.

The first section of steam-filled water injection temperature is 80 degrees Celsius, and the second and third sections of water injection temperature is 94 degrees Celsius. Other parameters were unchanged (powder amount 15g, ratio 1:16, three stages of water injection 30/120/90ml), and the total extraction time was 2 minutes and 40 seconds. By tasting, coffee flavor performance for the sour obvious, there is a green taste, a bit like the feeling of unripe fruit. The aftertaste has a hint of bitterness.

The phenomenon of powder layer when brewing in front street combination, the expansion degree of coffee powder layer is not large when steaming, and a part of steaming liquid flows into the lower pot, it is inferred that the green taste is caused by insufficient steaming. The bitter aftertaste may be due to the high temperature of the soaking water. Therefore, the front street has been adjusted several times for these situations, and the final parameters are as follows:

Powder amount 15g, ratio 1:16, grinding degree: hand mill No.20 sieve pass rate 80%(more fine powder), three stages of water injection are 25/125/90ml, reduce the steam water injection is to reduce the steam liquid into the pot ahead of time, but the water injection method needs to be more particular, otherwise it may cause a part of coffee powder in a dry state. The first stage of stewing water injection uses 83 degrees Celsius, stewing time is 35 seconds, and the stewing time is extended for better exhaust. The temperature used in the second and third stages is 93 degrees Celsius. Wait 2 minutes and 35 seconds for the coffee in the cup to drip completely. At this time, the flavor performance is rich in sour and sweet berry, the overall performance is balanced, the aftertaste tea feeling is obvious, and there is no bitter feeling.

If you also have the trouble of over-extraction, you may wish to try this method (thinking), pay attention to, do not copy the data, because the grinding degree of this thing is almost impossible to be exactly the same, the difference in the degree of fine powder also makes the data have no substantive significance, we can refer to the method of low temperature steaming, the temperature of the water injection can be higher than the usual 2 degrees. Finally, fine adjustments are made from the flavor results (stewing temperature, stewing time, extraction water temperature, etc.).