The method of making coffee

Just a bunch of facts, just a bunch of facts. Theory is the skeleton of facts, while practice is the truth of facts. To cook a good espresso, you have to face complicated practical problems. With a proper theoretical basis, we can improve our ability to understand problems.

Why is it so hard to cook espresso:

The problems with making a great espresso are mostly due to two factors: the uneven flow of water and the fact that the aroma of coffee is very volatile.

Problems with water flow:

Modern espresso machines can produce water pressure of 120 to 130 pounds, while coffee cakes are less than half an inch thick. The big problem with espresso comes from espresso's feature: using pressurized hot water to pass through a thin coffee cake.

Water has one characteristic:

He will always find the shortcut with the least resistance in the coffee powder, instead of trying to extract the soluble coffee oil. So a large part of this book is about how to make coffee powder evenly resistant to high-pressure water.

As long as the coffee filter cake has a little uneven density or the surface collapses, the high-pressure water will rush up and break through your door. In the coffee filter cake, the low density part will be over-extracted after the delicious ingredients flow out. On the other hand, the parts with higher density are not extracted enough. When this espresso flows out, the water flows in a spiral shape. The surface tension is relatively high and it is tightly attached to the outlet. In addition to the delicious reddish-brown liquid, there are white lines and small cups of coffee.

To cook a perfect espresso like this

Grind the correct amount of coffee powder, carefully flatten it and disperse it, and then rotate and grind it out after being evenly compacted with a filler. After being done, there should be some gaps between the surface of the coffee filter cake and the shunt net of the machine outlet. Turn on the filter head switch and the water will flow down and wet the coffee powder for about a second before the bubble head is really activated. This is called prepreg, which helps to seal the surface of the filter cake, and the delicious ingredients in the powder will not adhere so tightly after hot water contact, and it will be easier to extract when high-pressure water comes over. Because the cooking temperature is as high as 200 degrees Fahrenheit and the pressure is as high as 120 pounds. If the resistance of the filter cake is uneven, it will rush out of the hole or pore diameter, resulting in uneven extraction. The part of insufficient extraction will cause the yellowish-brown liquid of water in the outlet head, and the part of over-extraction will dissolve other substances and cause white stripes.