Is it good or bad to make coffee foam by hand? is it normal to have bubbles on coffee?

When making coffee, have you ever thought of what the foam on the surface is? When making some coffee, the foam will be very dense and rich, while when making some coffee, the foam will appear rare. What on earth is the reason?

Qianjie has also mentioned in the previous article that the golden foam burst out after steaming water injection is composed of coffee oil, air, very coarse powder and very fine powder. This also explains why the coffee foam has changed from a rich golden yellow at the beginning to a light white. After steaming, there is still a small part of the gas in the coffee powder, and when you continue to inject water, the oil will wrap the gas out, of course, these are very unstable bubbles, which are easy to burst, and then split into a number of small gases. Then go to the very coarse powder, because the particles of the coarse powder are slightly larger, there is a good chance that they will not be completely wet during steaming, so they will float on the surface in the subsequent cooking. With the continuous injection of water, the large granule coffee powder will sink after absorbing enough water. So it is also because the color is lighter and lighter in the back.

Finally, there is the part of very fine powder, which can not be eliminated if it is not screened, and Qianjie believes that there is no need to screen out ultra-fine powder. For example, many flavors in coffee are related to ultra-fine powder. If it is not a lot of ultra-fine powder, it does not have much effect on cooking. The last layer that makes up the surface foam is the very fine powder. Because the ultra-fine powder itself is light, it can easily float on the surface, as long as there is foam, the fine powder will float on the surface until the end.

The composition of these substances of the foam is destined to be unpleasant (because the pleasant parts are extracted), so it is reasonable for the Japanese traditional flushing method to raise the water level at the last stage of the current and cut off the river directly. Why is it that some coffee is rich in foam while others are rare? In front of the street, let me give you two examples. if everyone has brewed two kinds of beans, Mantenin Coffee and Rosa Coffee, they will clearly feel that the foam of Mantenin Coffee is very rich and dark, and the foam of Rosa Coffee appears light and thin.

This is because of the degree of roasting, deep-roasted coffee like Mantenin does not have more carbon dioxide, coupled with a loose structure, is very prone to rich coffee foam. On the other hand, light-roasted coffee, such as Rosa, is harder and still produces rich foam when freshly roasted, but the subsequent foam is noticeably scarce.

The bubble state of this situation is a normal phenomenon. But we can still judge the state of coffee by the state of foam. For example, when brewing coffee, coffee foam gushes out, indicating that the coffee is fresh, and if there are persistent atmospheric bubbles, it may be too fresh or not steamed enough. If there is no foam when making coffee, it may be that the grinding degree is too rough, or it may be that the coffee is not fresh. If the coffee foam is a big bubble, not delicate, many of the reasons are rough grinding. The bad taste of stale coffee is partly due to the loss of flavor, and partly because without coffee foam, the fine powder will sink to the bottom, and bitter substances will be extracted, making a cup of coffee bad.