What on earth is the layer of flowers floating on the surface of the coffee? The coffee oil in the concentrate

Author: yi zhang

Link: http://www.zhihu.com/question/20360485/answer/34507011

Source: Zhihu

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First of all, what is the layer of flower floating on the surface of the coffee?

Maybe no one will think too much about this problem.

But in the eyes of scientists, it is a mixture of two kinds of microfoam (microfoam), different colors, but you can enter me into you, so you can create patterns.

So to get such a flower, you have to mix the two kinds of foam together.

First of all, we have to have these two bubbles, and secondly, these two bubbles have to meet at the right time and in the right place.

So first, we have to have foam from coffee, crema.

The picture above is a picture of coffee fat, the black part below is coffee, and the brown red part above is coffee fat, which is obtained from coffee powder compacted by hot water that is nearly boiling and finely ground under high pressure. it is due to the refraction of coffee fat, other particles and air mixture to the air.

Chinese people generally don't drink espresso very much and think it's too bitter. In fact, when tasting espresso, the upper layer of coffee fat is important, and most of the flavor molecules are fat-soluble, so coffee fat is the soul of espresso flavor. it is also the key to judging the quality of a cup of espresso and baristas.

The above picture shows the microstructure of coffee fat foam, quoted from Ernesto Illy& Luciano Navarini

The presence of coffee fat is often seen as a sign of the quality of espresso, which accounts for more than 10% of espresso in volume. Coffee fat contains a lot of gases, about half of the total volume.

In the image below, when you look at the structure of coffee fat under an optical microscope, you can see that it contains bubbles, fat particles (usually less than 10 microns) and some solid particles (fragments of the cell wall of coffee beans). Quoted from the right [Coffee pull: foam Waltz]

The amount of coffee fat foam is not only related to the coffee beans themselves, but also related to the packing technology, that is, the action of putting coffee powder into a small container and then pressing it, the tighter the pressure, the easier it is to extract the coffee fat, but if it is too tight, the coffee may not flow out, so it is very skillful.