The process of coffee extraction the relationship between grinding and extraction of coffee beans

From: Yun Fei private baking (if you have a dream, take good care of her) 2013-07-17 12:17:19

As a barista, you can't change the facilities in the store, such as the brand of the coffee machine, the choice of the water purifier, the temperature of the cooking head, the specification of the powder bowl on the handle, which cannot be changed as an employee. However, this is also the best reflection of the ability of a barista. How to extract the best cup of coffee under the existing conditions.

Of course, there is not much we can change but it is important enough. This is my coffee shop less than a year of work, look at the materials, go to different cafes, drink coffee, learn some knowledge about extraction, can be regarded as a summary, but also the integration of their own knowledge of espresso at this stage.

To get back to the point, let's take a look at the basic principle of Italian extraction and the influence of several variables on the formation of coffee flavor, mainly in terms of 4: 1 grinding degree, 2 powder quantity, 3 pressing powder strength and 4 coffee bean freshness.

Let's start to extract a cup of coffee.

[1]

From turning on the extraction button, about 1-6 seconds, the water in the brewing head has not yet come into contact with the coffee pressed powder, and there will be some reactions that are invisible to our naked eyes. To put it simply, the two flavors in our taste, flavor (mainly acid) and mellowness (mainly bitter), that is, water will merge with the flavor substances in nitrogen dioxide and almost absorb all the flavor substances in coffee. The sour taste is the first to blend with water, while the other flavor of coffee, the bitter taste, will be released slowly at a uniform speed. At the same time, the water began to come into contact with pressed powder slowly.

At this stage, the effects of four variables on coffee are summarized.

1 the thickness of grinding. The finer the grinding degree, the largest contact area between coffee and water, and the largest amount of flavor substances will be obtained, which almost determines all the flavor substances and part of the mellowness, and the plumpness here is negligible compared to the long extraction of 30 seconds.

2 powder quantity, the powder quantity here has not affected the taste of a cup of coffee.

(3) the strength of powder pressing, the greater the strength, the more compact the pressed powder on the surface, and the greater the resistance to water. Determines how long the water stays on the surface.

4freshness of coffee beans. The fresher the coffee, the higher the carbon dioxide content, the deeper the roasting degree, the higher the carbon dioxide content, so the greater the resistance. That's why, when expired beans are extracted, the flow rate is like a spring (exaggerated.)

[2]

Let's take a look at the second stage for 5-10 seconds. In the first stage, the water has come into contact with the top powder layer. Due to the powder compactor, the tighter the powder is, the longer the water stays on the surface of the coffee. Slowly, the water passes through the loose pressed powder at the lower end of the pressed powder, which has a shorter residence time, resulting in lower extraction efficiency. After that, the coffee pressed powder is soaked in water, which opens the channel for the water behind it. The handle began to slowly flow out of coffee liquid as thick as honey. At this time, the concentration of coffee liquid is as high as 25%, and the acid-based coffee liquid is too strong to be imported. Because the sour taste is the first to dissolve with water, it does not mean that there is no bitterness at this stage, but that the strong acid far suppresses the bitterness.

You can taste the difference between the taste of coffee extracted for 10 s, 20 s and 30 s.

At this stage, the effects of four variables on coffee are summarized.

1 the thickness of the grinding degree, the flavor substances at this stage are basically absorbed in the first 5 seconds, and begin to weaken at this stage.

2 the amount of powder, if more, pressed powder thick, will increase the mellowness of coffee. The rate of change in color means the amount of powder. Because too little powder will prematurely let the hot water open the road. Thus reducing its plumpness.

3 pressing powder strength, because in the previous stage, the most compact powder layer of the upper layer has been soaked by water, which has little effect here.

(4) the freshness of coffee, the higher the content of carbon dioxide, the deeper the baking degree, the higher the content of carbon dioxide, so the higher the expansion, the greater the resistance. We can see that very fresh coffee produces large bubbles in the process of extraction. This will cause uneven extraction between the left and right sides, even if our pressing powder is correct. That's why you need to wake up when making espresso.

[3]

In the next stage, 11-15 seconds of extraction, when high-temperature and high-pressure water passes through the layers of pressed powder and takes away the first batch of coffee liquid with the highest concentration, pressed powder is soaked and expanded to find a way out and open the channel for subsequent water. After that, the flow rate of the coffee liquid will speed up, the color of the coffee liquid will gradually become lighter, and at this stage, the bitter substances will be released at a uniform rate.

So let's move on to the influence of four more variables.

The grinding degree of a coffee, the pressed powder has been completely soaked and the channel has been opened, which is no longer so important here.

The amount of two powders, at this time, the more the amount of powder, the higher the degree of alcohol, while the amount of powder decreases, the degree of alcohol will naturally weaken, and what you need to think about at this time is that the amount of powder increases, and in order to ensure the normal flow rate, the degree of grinding should be thickened, so that the flavor will be weakened accordingly.

The strength of three pressing powder has no effect.

Four freshness, the more fresh, the higher the carbon dioxide content, the longer the baking time, the higher the carbon dioxide content, so the higher the expansion, the greater the resistance. It should be reminded here that too much carbon dioxide in the process of hot water will affect the stability of the extraction. We can see that very fresh coffee produces large bubbles in the process of extraction. This will cause uneven extraction between the left and right sides, even if our pressing powder is correct.

[4]

The time after 15 seconds

Emma, it's finally the end. I'm so tired to write a journal. The key is to use your head and do it. Finally, cut off the extraction time, which is also crucial, because the difference of one second will make the coffee have a different taste.

At this time, the coffee liquid begins to turn yellow, but at this time the coffee still has a high concentration, rich taste and main acid. If we choose to cut it off in 15 seconds, we will get a cup of ristretto (concentrated espresso) in order to get a cup of coffee with a more balanced taste, what we do is to wait for the moment when the brown color turns golden, according to experience, the coffee should be the most balanced espresso.

Of course, there will be some differences in different baking degrees, just like lightly baked beans. It may need to wait for the color to be a little more yellow and choose to cut it off in order to better balance the taste.

All right, let's take a look at the effects of the four variables in this final stage.

1 the degree of grinding of coffee, the channel is completely open, almost no effect.

2 the amount of powder still has a great impact, at this time, if the amount of powder is more, we will get a thicker espresso, if the amount of powder is less, our consistency, or mellow feeling will be weakened accordingly. (thinking about the problem, there is too much powder, in order to maintain a normal flow rate, grinding is bound to be thicker, which means that the flavor of coffee may be weakened.)

3. The strength of powder pressing has no effect at this stage.

4 the freshness of coffee is not mentioned in Zhe's Douban diary. What I am thinking now is that, after all, water has taken away some flavor substances and some coffee liquid, and the concentration of carbon dioxide will be reduced. At this time, even if there will be an impact, it will be a small amount.

After watching Zhe's commentary on the extraction of espresso in the past two years, I also learned a lot from it. 90% of the above content is, after seeing it n times, I try to say it in my head, and then write it again in the book, and finally put it on the computer to appear in the form of an electronic version. You are welcome to point out what you do not understand.

I hope that every partner who joins in the coffee industry will continue according to his original wish.

I hope I can quickly learn to have a good control over coffee and present a good cup of coffee to every customer.

What about you?

Source: http://www.douban.com/group/topic/41447306/