Is there any grease foam in hand-made coffee? What does the foam of hand-brewed coffee taste like?

Careful friends should have found that when making coffee, the liquid surface of the filter cup will float with a layer of foam, and the foam will behave differently according to the brewing beans and time. Sometimes the foam is very rich, and sometimes it is very rare, sometimes brown and sometimes white.

What effect does the foam of coffee have on us making coffee? Or what kind of cooking information we can get from the state of foam. Let's let Qianjie discuss it. When water is injected into the coffee after steaming, the coffee powder will burst into golden foam, which is mainly composed of carbon dioxide, oil, large particles of coffee powder and a small amount of fine powder. Among them, the influence on the color of foam is mainly caused by large granules of coffee powder.

In our daily coffee brewing, by constantly injecting water, the foam of coffee slowly changes from dark yellow to light white, which is actually the sinking of large particles of coffee powder floating on the surface. The principle is also very simple. During steaming, most coffee powder emits gas, but it is not completely discharged. For coffee powder with larger particles, water permeates more slowly, so it takes longer to release gas. When injected with water, these large granules of coffee powder float on the surface because of their light weight. The subsequent water injection will wash down the coffee powder, so that the color of the foam will become lighter.

Therefore, when injecting water, the coffee bean foam is washed out first, and the extent of the circle is determined according to the depth of the foam color when circling. For example, when only injecting water around a large circle, the foam in the middle will be darker than the outer ring, so when you see this, you need to slowly shrink the circle and wash down the coffee powder in the center circle. "you can also see the situation when injecting water by looking at the uniformity of the color of the foam." when making different coffee beans, the richness of the foam is not quite the same. Some coffee is very rich in foam, some are very thin, and even foam voids appear on the liquid surface. There are two main reasons that affect the foam richness, one is the baking degree, the other is the freshness.

Deep-roasted coffee beans are rich in oil and carbon dioxide, and because the texture of coffee is loose, coffee powder is easy to float on the surface, so the foam is more abundant. The lighter roasted coffee beans have relatively less oil and carbon dioxide, and the coffee beans are more dense, so there is less coffee powder floating on the surface. In brewing some shallow roasted coffee, it is also a normal phenomenon that the foam on the liquid level of coffee decreases gradually in the process of falling after water injection. The thin foam clings to the edge of the filter paper as the liquid level drops.

Similarly, the richness of the foam is also related to the freshness of the coffee beans, because the foam is made up of coffee oil and carbon dioxide, and when the coffee beans are not long roasted and are still in a very fresh state, then the water injection after steaming will be very rich in foam.

When the coffee beans are stored for a long time, the carbon dioxide in the coffee beans is almost exhausted, so when flushing, the amount of foam released is less. Therefore, when making coffee every day, we can judge the roasting degree of coffee according to the performance of the foam. for example, the color and taste description of some coffee beans are similar to each other, so we can observe the richness of the foam to distinguish them. We can also judge the freshness of coffee beans, which is generally combined with the degree of steaming expansion. The mode of water injection can also be adjusted through the state of foam.