The thinking mode of extraction 2b-extraction time is transferred from Douban

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Extraction time, which looks easy, is actually a little more complicated than expected. Because although the extraction time is directly related to the relationship between extraction rate and concentration, their relationship is not necessarily proportional. We still return to the original two purposes, get the reasonable extraction rate and get the proper concentration. Let's start with the extraction rate and then talk about the concentration. In the process, http://www.douban.com/note/239651602/ 's article can be reviewed at any time.

Before we officially get to the topic, we also need to clarify the concept of what exactly is extraction time. This articulation is important because in a narrow sense, low-pressure pre-soaking or steaming is not a formal extraction. For example, many coffee machines calculate the extraction time, excluding pre-soaking. It was only at nine atmospheres that the clock began. But in fact, if the extraction is water in contact with coffee powder to take away the soluble matter, then the extraction time should include any time, the process of contact between water and coffee powder, which naturally covers pre-soaking and steaming.

* extraction rate

If coffee comes into contact with water, the soluble matter in coffee will be gradually taken away with the passage of time. We hope to achieve an extraction rate of 18-21%. At the same time, the maximum amount of substances taken away by coffee will not exceed 30%. Therefore, the relationship between extraction time and extraction rate is proportional. That is, the longer the extraction time, the higher your extraction rate.

Yes, it's very intuitive. But in practical application, many friends make espresso, when debugging, they are more concerned about adjusting the grinder, or fiddling with the amount of powder. In fact, sometimes with a slight change in extraction time, more extraction (higher extraction rate) and less extraction for 2 seconds (lower extraction rate), you will get a completely different effect. How to judge? Since the extraction time is proportional to the extraction rate, under the premise that the amount of powder is the same, you can judge by the espresso liquid color. You can see the color changes during espresso extraction (http://www.douban.com/photos/album/65323274/)

If we use the figure, the arrow indicates the direction of time advance, and the extraction time will be proportional to the extraction rate. It should be emphasized here that with the approach of 30% extraction rate, the extraction rate of soluble matter will be slower and slower. (this will be described in the next chapter. )

* concentration

The longer the extraction time, the higher or lower the concentration? It actually depends on what kind of extraction method, if it is the way of soaking, such as pressure? If we add 10g of powder, we fix about 170g of water. So in the process of contact between the water and the coffee powder, there is no new water filling, which means that the soluble matter in the coffee powder gradually melts into the water. It also means that in this fixed 170g water, the longer the time is, the higher the extraction rate is, and the higher the concentration will be.

What about the way water passes through? That is, a continuous supply of water is extracted through coffee powder, so as the time goes on, the more water passes through, the coffee will be more and more diluted. This can also explain that if you extract it on an Italian machine for 1 minute, you will not only get a very mixed cup of coffee, but also mean that your cup of coffee is relatively light. For example, if you make coffee by hand, you should have extracted 320g of water, but if you extract 500g of water at once, the extraction time of 500g of water will be longer and the taste will be lighter.

Integration

Yes, it's all intuitive. There's nothing new. But as I mentioned at the beginning, the most important thing in making coffee is to get a reasonable extraction rate and concentration. Therefore, when we change the extraction parameters of current coffee, it is very helpful to know whether it is infiltration or soaking. So, let's do an integration.

Back to the basis of extraction. If we use soaking. This means that CBR (the ratio of Coffee Brewing Ratio coffee to coffee liquid) is fixed. Because the amount of powder is put into the kettle, or the siphon pot, this will not change, and the water will not change the amount of powder. Therefore, with the change of extraction time, the extraction point of coffee will move along this line of CBR. That is, with the change of time, the extraction rate and concentration will continue to increase until the extraction rate of 30%.

And the way water passes through? It's a little complicated in the picture. Because water is a continuous supply of coffee powder, and take away the corresponding substances. So the denominator in CBR, the weight of coffee, is changing all the time, which means that CBR is also changing. Of course, one thing we can fix is the amount of powder.

This time, let's take Espresso as an example. (note, it is no longer CBR, but EBF, espresso brewing formula, but the formula is still the same, gram weight divided by coffee gram weight), assuming that in the first second, the coffee liquid comes out of the first drop, then the first drop of gram weight is almost negligible, infinitely small. Then the value of coffee powder weight and coffee liquid ratio (Dose/Espresso Weight) because the denominator is infinitely small, then the whole EBF value is infinitely large, which is an almost vertical line in the figure.

With the passage of time, there is more and more coffee in EBF, which means that the line of EBF begins to tilt downward. Just imagine, if we care about machine extraction for a few minutes, then the line of espresso weight, when coffee is infinitely heavy, means that the line of EBF is almost horizontal.

Another point that needs to be involved here is that people will want to extract espresso. The flow rate is slow at first, and then the flow rate increases as the coffee powder takes away more and more substances. Therefore, with the change of unit time, the tilting speed of EBF is faster and faster.

So what does this mean? The production of the pass type will be very complicated, because if we change the degree of grinding, the extraction point will slide along the line of EBF, and the EBF will change over time. This naturally involves the specific method of extraction. But what we can find is that with the change of time, through the production of class, the extraction rate will be higher and higher, and the concentration will be lower and lower. (changes in red dots on the picture)

Roughly, this is the relationship between the extraction time and the production of coffee, and we will discuss the extraction efficiency in the next chapter. But as I said at the beginning of this series, in the end, no matter what the method is, the purpose of our extraction is to find a reasonable extraction rate and concentration, and the extraction is uniform.

P.S. In fact, there is also a combination, that is, soaking and passing. Like the Smart Cup. You can think about what the change between extraction rate and concentration would be if you started with the extraction time. I will update this picture in a week.

Source: http://www.douban.com/note/261329974/