The difference between crema and American Coffee in espresso

The difference between crema and American coffee in espresso,

If the cooking condition of espresso is Overestracted espresso, its crema color will be dark, and it will appear dark with a slightly black edge. On the other hand, if it is Under-extracted espresso, then the crema color is light, appears light golden yellow, and the texture is thin. Common examples are high cooking water temperature (above 93 degrees Celsius), slow flow rate, darker crema color, lower cooking water temperature (below 88 degrees Celsius), faster flow rate, lighter crema color. The higher the BrewingRatio of espresso, the darker the crema color, and vice versa. To put it simply, if you use more coffee powder, the smaller the espresso, the darker the crema will be. For example, Ristretto with 100% flush rate, its crema color is usually darker and must be darker than espresso with 50% flush rate. The espresso color with a relative flushing rate of 50% is also darker than the Lungo with a flushing rate of 33%. This is why many world flower draw champions (such as Yoshi Sawada) are accustomed to using triple filters to flush out more than 100% of the Ristretto as the subbase of the latte, because this can get the darkest background color and the most contrast effect.

To produce stable bubbles, we need some bubbles and some compounds to "wrap" the bubbles, making the bubble structure stable and elastic. The process of this chemical reaction can be thought of as the role of a surfactant. Unlike milk bubbles, which do this through egg whites, coffee uses a substance called protein melanin. It is produced by a chemical reaction of a group of mixtures during baking. In fact, scientists do not know much about the process. Neither protein nor melanin is hydrophilic, so when hot water strikes, they are naturally distributed on the surface of bubbles, so they can come into contact with more air, resulting in countless small bubbles, so we have-bubbles. There are other things-fat (the author refers to both oil and fat, fat is solid, oil is liquid), the presence of oil often destroys the structure of foam (think about it, when we make a cake, we have to remove the yolk, otherwise the fat in the yolk will lead to the failure of egg whites (that is, quickly stirring egg whites and beating them into milk bubbles).

So will the oil in the coffee cause crema to disappear quickly in a few minutes? The answer is both right and wrong. The surfactant is dissolved in water, and due to the action of gravity, the surfactant of the bubble surface will be pulled off the surface of the foam together with the water, making the foam fragile, robbing elasticity, and then quickly disappearing. The speed at which the foam disappears is related to the speed at which the water is dragged away, but the foam on the surface of a cup of coffee lasts much longer than that of a cup of fast-flushing coffee, because the liquid is much thicker than that made quickly. this is also confirmed by our taste.