What is coffee fat (Crema)? Deconstructing the Oil Secret of espresso

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The espresso that everyone likes to drink is based on espresso (Espresso), so a good cup of espresso can be called the soul of coffee. When it comes to espresso, oil must be an important indicator that can not be ignored. Because oil not only gives espresso important visual characteristics, but also changes the flavor and taste of espresso to some extent. But what exactly is this layer of grease?

The manufacturing process of grease

To understand how these oils are produced, you must first understand the process of making espresso. Take a professional espresso machine as an example, use 18 to 20 grams of coffee powder and extract 35 to 40 grams of espresso at 9 atmospheric pressure (9 Bar). High temperature, high pressure, with the right coffee powder, can make a cup of espresso.

When espresso is first extracted, there will be a golden to chocolate grease on the surface; this layer of oil is inextricably linked to pressure. When the water is heated and pressurized, the soluble substances in the coffee powder layer will be extracted, and this process will emulsify the natural fat and oil in the coffee. At the same time, freshly roasted coffee beans contain carbon dioxide, which is under pressure and melted into coffee in the process of making espresso. However, when hot water flows through the coffee pressed powder and comes out of the powder bowl, it can return from nine atmospheres to the normal one. At this time, because of the pressure gap, the carbon dioxide expands, and the oil wraps the carbon dioxide, and because the oil is lighter than water, it forms the so-called grease.

Grease = good espresso?

Oil reflects the condition of raw coffee beans. The more fat, the more natural oil content of coffee beans, that is, the freshness of coffee beans. However, coffee with fat does not necessarily mean that it is a good espresso, such as Robusta (extended Reading: have you had the right coffee? (coffee beans are rich in oil.

Espresso is actually the most direct and simple way to show the original flavor of coffee, so poor beans, poor grinding, poor powder pressing, improper machine operation, too short or too long extraction time, etc., will affect the flavor of a cup of espresso. So the next time you have an espresso, don't rush to judge whether the coffee is good or bad by fat.

A good espresso should taste well-balanced, round and smooth in the mouth, and have the flavor of the place of origin (fruit acid, flower flavor, etc.), not blindly bitter. Remember to take a sip slowly, taste the flavor, and you may like to drink espresso from now on.