The soul of Italian coffee! Five Factors Affecting the Extraction of Espresso

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What is condensed?

The original concentrated text is "Espresso". Coffee beans are extracted in a short period of time through a semi-automatic or fully automatic coffee machine using temperature and pressure after proper grinding and powder use.

Define the conditions for Espresso:

Pressure: 9 bar ±2

Temperature: 90.5 ~ 96 °C

Time: 20: 30 sec

Powder content: 7x 10g (single)

Extraction amount: 30ml ±5

The most fascinating thing about Espresso is the golden foam on the surface, how to produce it? When the coffee is roasted, the cell wall of the coffee will be filled with a lot of gas, which will be discharged slowly over time.

In the process of extraction, the ground coffee powder is soaked in hot water, and the gas will be squeezed out of the surface of the cell wall in the case of hot expansion and cold contraction; and the coffee extracted by hot water also contains some oily substances, which can allow the coffee liquid to be emulsified by the way of emulsification. the gas is coated with the squeezed gas, resulting in dense bubbles.

On the other hand, if the surface of the foam is similar to the leopard print, it is because the broken cell wall particles are brought out by high pressure extraction, and the broken cell wall floats on the surface, resulting in color contrast.

Factors affecting the extraction of Italian Coffee

According to the concept of Golden Cup Theory (Gold Cup) put forward by SCAE (European Fine Coffee Association, Speciality Coffee Association of Europe) in 1960, he explained that when coffee powder came into contact with water, it would dissolve the substance in coffee powder through water. On the other hand, only 30% of the substances in coffee can be dissolved in water, and the remaining 70% are insoluble structures (mostly wood structures); of these, 1% of 30% of the substances are extracts that we do not want to appear.

Therefore, when the coffee flavor can perform best, the extraction rate must be controlled at about 20%. Therefore, we need to change the extraction results we need by changing different extraction factors.

The factors we need to control are roughly divided into the following: but each factor can be discussed in more depth. Today, we will briefly explain:

Powder quantity

Fill the powder according to the size of the powder bowl, when the powder is loaded into the powder bowl and pressed, the reserved space should not be higher than the thickness of the boiled head protruding washer (water distribution network), otherwise it will cause the phenomenon that it can not be put on. Too low filling powder will cause uneven extraction. The boiled head and strainer leave about room for 1mm.

Grinding thickness

After determining the amount of powder used, the thickness of the coffee powder will affect the density in the powder bowl. Under the same amount of powder, if the coffee powder is thicker, the density of coffee pressed powder will be lower. On the contrary, the finer the coffee powder, the higher the density of the coffee pressed powder. The density of pressed powder affects the extraction time. When water with the same pressure passes through pressed powder of different density, the high-density pressed powder will make the flow more difficult, and the low-density pressed powder will pass faster.

The only reason that can change the extraction speed is "grinding thickness".

Temperature.

Temperature also plays a very important role in Espresso extraction, and different temperatures also affect the extraction rate under other same conditions: higher temperature has higher extraction rate, whereas lower temperature leads to poor extraction rate. According to the competition rules of WBC (World Barista Championship), 90.5 ~ 96 °C is a better temperature for extraction and concentration, but in order to obtain correct temperature information, we must rely on the understanding and experience of the equipment and other instruments. If the water temperature is too low, the color of the coffee extracted will be lighter, and the bitterness and flavor will be less obvious, because there are fewer aromatic substances extracted, so it is easy to mask the bitter taste of the coffee. The coffee substance with high water temperature is easy to be released, and it is relatively easy to extract some unpleasant bitterness, scorch, astringency and so on.

Extraction time

The conditions affecting the extraction time of Espresso are "the amount of coffee powder and the thickness of grinding", and these two directions will change the extraction time. According to the rule of thumb, the best range of extraction with a double powder bowl is 20 to 30 seconds, but this is not an absolute range; sometimes the conditions of the machine or the coffee bean itself are different, so you can boldly try different extraction times and get different flavor lines. Extraction time is too short, hot water through coffee pressed powder time is short, it is not easy to show the sweet flavor of coffee, Crema color is easy to be light. If the extraction time is too long, the hot water passes through the coffee pressed powder for a long time, the flavor of coffee is easy to be over-extracted, the bitterness and astringency of coffee are easy to show, and the color of Crema is obviously dark.

Extraction dose

In determining the dose, there is a standard method of production in Italy, and it is recommended to extract the dose of 50~60cc in a powder bowl with two parts of powder. It is suggested that the method of segmented extraction should be used to determine the appropriate time point; first prepare several cups of the same size and pick them up separately by segmented extraction under the condition of fixed particle fineness, extraction temperature and extraction time; taste the coffee extracted at different time points, you can obviously feel that different coffee flavors will be extracted at different time points. In this way, the end point of extraction concentration can be fully understood, and the best performance point of beans can be easily grasped quickly.

Some references: the Coffee Bible

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