How to make espresso and cold extract coffee? Recommendation of cold extracted coffee beans for special coffee

Before writing this article, the code clerk asked several coffee practitioners / enthusiasts: "do you think that under normal circumstances, soaking cold extracted coffee, using the same amount of water, coffee beans, coffee powder, extraction container, and extraction time?" how to increase the extraction concentration of coffee? " I believe everyone, like several interviewees, will reply: "it must be fine-tuning!"

Indeed, since we came into contact with coffee brewing, the theory we have received is that the finer the coffee powder, the stronger the taste, the thicker the coffee powder, the lighter the taste. But there is a premise for this information, that is, high temperature extraction / coffee powder layer flipping state. As a low-temperature static extraction of cold extracted coffee, this theory can not be used, why? The effect of water temperature-particle movement on the extraction of coffee the higher the temperature of water is, the more heat increases the movement of molecules. When the thermal motion of the molecules is countered by the attraction between the solid molecules, the solid molecules will be dispersed. At the same time, molecular thermal motion increases the number of contacts between water molecules and solid molecules (coffee particles), so when coffee is ground finer, solid molecules dissolve faster & more.

When the temperature of water is close to room temperature / zero, the movement of molecules will also be reduced / zero. Without the counterbalance of molecular thermal motion and the attraction between solid molecules, coffee particles will "clump", that is, caking. So when the coffee is ground finely, the hugging situation will be so large that the coffee powder in the middle of the ball can not be fully extracted.

When making coffee by hand, the high water temperature and the impact of water flow during water injection make the powder layer in a continuous tumbling state, so the extraction rate will also increase rapidly. If the coffee is ground too fine in this case, it is prone to over-extraction.

In cold extraction / cold brewing coffee, we need to add water and stir evenly and put it in the refrigerator for more than 12 hours, during which the temperature will remain low, so even if it is stirred evenly, some of the particles will still be "clustered" extraction, so a small part of the coffee powder in the whole coffee extraction process has not been effectively extracted.

Can coarse grinding effectively improve the extraction rate of cold-extracted coffee? Qianjie did a small experiment ~ this time Qianjie washed coffee beans with water from the Yega Sheffield Tintin Cooperative in Ethiopia, soaked 30g coffee powder in the same container & normal temperature water of the same quality with 1:10 powder-water ratio, the grinding degree was EK43s#9 (fine grinding) and EK43s#10.5 (coarse grinding), and then soaked at a low temperature in the freezer for 16 hours.

After the extraction, the coffee juice was filtered with normal temperature filter cup, dry filter paper and clean container at room temperature, and then the concentration was measured by TDS meter. The final test results show that the TDS of fine-ground cold-extracted coffee liquid is 2.10%, and the TDS of coarse-ground cold-extracted coffee liquid is 2.20%. The cold extracted coffee with fine grinding will show bright citrus acid, honey and micro-tea, while the cold coffee with coarse grinding will show brighter citrus acid, sweetness and tea. It feels like sugar-free lemon tea.

The main reason for this experiment is that many friends asked Qianjie how to thicken the cold-extracted coffee to make special coffee, but they did not want to be overly obscured by other ingredients. If you want to extract cold-extracted coffee with just the right concentration without dilution, Qianjie recommends fine grinding with a powder-to-water ratio of 1:13 to 1:15. Although adjusting the coarse grinding degree can improve the extraction rate & concentration, not all coffee beans / cold extraction methods are suitable to do so! Coffee beans that are too shallow or too deep-roasted cannot increase the extraction rate and concentration in this way because they are prone to irritating acidity or unpleasant bitterness.

There are electric cold bubble bottles on the market that can make cold extracted coffee for a short time. The principle is that the device will constantly shake the filter up and down to make the powder layer move. In this case, it is more suitable to use fine grinding for extraction. -this experiment is based on the common way of cold brewing coffee.