What is espresso? Espresso is a very small cup of coffee,大概 two or three sips and it's gone. Its taste is very strong, and many people find it hard to accept. The small cup size and strong taste are the reasons why espresso has a small audience in China, but latte with milk and Americano with water are very popular.

The appearance of espresso in the cup is dark espresso liquid at the bottom, with a layer of golden coffee crema floating on top. Is coffee crema oil?

We all know that peanut oil is extracted from peanuts, and the surface of dark-roasted coffee beans will seep oil. So what is the layer of crema pressed out by the coffee machine made of?

Italians call this layer "Crema", and this unique and rich Crema can only be made by an espresso machine, and the key lies in the pressure. An espresso machine generates a 9-bar water pressure to "squeeze" the coffee puck. Because the pressure is too high, the carbon dioxide in the coffee grounds becomes supersaturated with water, so the carbon dioxide cannot be released and directly dissolves into the coffee liquid. During the extraction process, the fats in the coffee are emulsified. These fats wrap around the carbon dioxide. Since they are lighter than water, they gradually separate, and the golden crema appears on the surface, very beautiful.

So this golden, delicate coffee crema is formed by the insoluble oils in coffee wrapping around carbon dioxide. So how can espresso have a beautifulCrema?

In Front Street's view, high-quality Crema is golden yellow, with a delicate surface, uniform color, and when shaken, it is as smooth as cream, with an obvious clinging to the wall. It not only gives espresso a good visual effect, but also enriches the mouthfeel and aroma when tasting, protects the flavor of the coffee, and when making hot milk coffee, it is more conducive to latte art integration and supporting the pattern. Perhaps these are the reasons why people go to great lengths to pursue a perfect Espresso!

Based on past extraction experience, Front Street believes that getting a rich Crema is actually very simple. First, when buying coffee beans, you need to choose beans with high oil richness and sufficient carbon dioxide, such as medium-dark roast, within the flavor period (45-60 days), or fresh espresso blend beans with a certain proportion of Robusta. For example, on the bean list of Front Street Coffee (FrontStreet Coffee), the two espresso blends "Front Street Commercial Blend" and "Front Street Classic Blend" are precisely because they are mixed with a small amount of Robusta beans, making it easy for the espresso to show a beautiful crema.

Once the right coffee beans are selected, they must be paired with fresh grinding, stable high temperature, sufficient extraction pressure, and reasonable extraction parameters. Only by satisfying these key factors can you get an Espresso rich in dense crema.

In general, the fresher the beans, the darker the roast, the greater the pressure and the more stable the performance of the equipment, the better the expression of coffee crema. Next, we will analyze specific cases. Front Street will teach everyone how to judge the quality of Espresso by observing the form of the crema, thereby solving various common extraction problems.

No crema at all, or thin crema: The problem is likely that the beans have been stored too long (including improper storage and coffee beans being pre-ground into powder). The longer the storage time, the more the coffee beans exchange gases with the air, the more carbon dioxide is lost, and the less coffee crema is finally presented. Secondly, too little pressure from the coffee machine, too low temperature, too coarse grind, insufficient tamping force... are also causes of too little crema.

Whitish crema: If the espresso you extract has a good thickness of crema but lacks a golden color and the overall taste is rather sour, then it is likely because you used beans with a lighter roast. For example, using pour-over beans that highlight fruity acidity to make espresso can easily result in an unpleasant sourness due to insufficient extraction, accompanied by whitish crema.

Rough, bubbly crema: This kind of espresso Crema often lasts a very short time and dissipates quickly. This is caused by coffee beans being too fresh. Freshly roasted beans contain a large amount of carbon dioxide. When a large amount of gas is pressed into the coffee liquid, the emulsified oils cannot wrap the gas and easily collapse.

Clumpy crema: This kind of espresso usually shows obvious "lumps" when shaken, with an uneven surface of crema and poor fluidity, just like milk foam that we have frothed for too long, making it difficult to spread and blend.

The above content is compiled by CoffeeHunters, a coffee news website.