Italian espresso how many milliliters of espresso common extraction problems and correct practices

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What is espresso espresso, also known as "Espresso", is a coffee drink or espresso base derived from Italy, which is quickly extracted under high pressure. The traditional capacity of a single espresso is about one ounce. The international general technical standard is as follows: about 7 grams of freshly ground coffee powder, using water at a temperature of 92 degrees under the pressure of about 9Bar, after 20-30ml extraction for 30 seconds to get a cup of coffee about 20-30ml, the surface of this coffee should be covered with coffee oil. With the process of coffee boutique, some new coffee theoretical knowledge has been disclosed, coupled with the blooming of a hundred flowers in many independent cafes, the Italian extraction schemes are also slightly different. As for the former street coffee standard, a cup of espresso was based on 2 shot (1 serving of espresso) and 38g espresso was extracted with 19g coffee powder at 1:2 for 28 seconds. Why are the extraction parameters of most domestic coffee shops now changed to grams instead of milliliters? It's a matter of density. What a cup of espresso can see is dark espresso and floating coffee oil, which is small in density, large in size, and can't guarantee the same coffee oil in every cup all the time. All the weight measurement will be more accurate.

How to understand the underextraction and over-extraction of espresso? Excessive extraction often leads to dark coffee liquids and oils (Crema), sometimes producing obvious air bubbles floating on the liquid surface, usually taking too long to extract (for example, more than 1 minute), and more than 10 seconds to see the first drop of coffee liquid. There are many reasons for excessive extraction, the common ones are: coffee powder is too fine grinding, water temperature is too high, extraction pressure is too high, filling pressure channel is too strong, and so on. Insufficient extraction is contrary to excessive extraction, which usually means that there are still many unextracted aromatic molecules in coffee powder, but the default extraction time is over, that is, the extraction rate is generally known to be less than 18%. When the extraction is insufficient, the coffee liquid may be light yellow and lack coffee oil. the extraction time is usually too short (for example, the extraction is completed in 15 seconds), and the coffee is released like a stream of water under pressure. instead of the sticky feeling of honey flowing down during normal extraction, the above phenomena are all signs of insufficient extraction. In addition to these theoretical problems, there are also some problems that often occur in the extraction of espresso, such as:

When using a double-guide handle to extract and concentrate, the coffee liquid always drips from one side first. There are three main reasons for this problem. First, first confirm whether there is a coffee residue blockage in the water distribution network of the cooking head, and observe whether the water flow of the cooking head is evenly distributed. If you find that the water flow is deviated to one side, you need to clean the cooking head and the water distribution network. The second is whether the pressing powder is flat, if the pressed powder is high on one side and low on the other, it will cause the water to infiltrate too fast to the low side, causing the liquid to flow out from one side first. The third is to observe whether the coffee machine or table is level with the ground, in many cases, it is found that the first two situations occur, but the coffee machine or table uneven causes the coffee machine to tilt, so that the liquid will flow out from one side first.

What is the reason for caking of coffee oil? The production of coffee oil is the combination of air and soluble fat in coffee due to the high temperature and high pressure in the brewing process. If the coffee beans are too fresh and contain too much gas, they will make the oil too rich (thick). And too fresh beans will be very unstable, pressed oil will be very rough, put for a long time will solidify and agglomerate. Therefore, it is found that the caking phenomenon of oil is likely to be that the coffee beans are too fresh, and the best solution is to store them for more than a few days and then use them after the bean cultivation period.

Is the tiger spot oil on the surface of espresso normal? Tiger spot oil means that there are dark spots on the surface of the oil, which looks like tiger spot. In fact, the dark spots on the oil are some very fine powders, which may be caused by too much fine powder produced by the bean grinder, thicker pore size of the powder bowl, or excessive pressure extracted by the coffee machine, as well as rough grinding plus heavy filling, the fine powder is easy to move down and into the esprsso cup through the filter cup, which will cause dark tiger spots on the surface of Crema, making the Crema look dark.

In fact, whether there are tiger spots does not have much impact on the flavor of espresso, the body of espresso with tiger spots will be fuller, but if too much fine powder will be counterproductive, resulting in rough taste.