What is the standard for gold cup extraction? How should the extraction rate and concentration of coffee be calculated?

"Golden cup extraction" is a concept that often pops up in the field of hand-brewed coffee. A lot of coffee brewing teaching will mention this word from time to time. Perhaps most Xiaobai friends will feel strange to it, and what they often retrieve on the Internet are numbers and pictures that they do not quite understand, so today, Qianjie will take you to review what is Golden Cup extraction!

What is gold cup extraction? As Qianjie said, gold cup extraction belongs to a concept, what it conveys is that coffee has a most popular extraction range, and as long as the coffee we brew out is in this range, then the taste of this cup of coffee is acceptable to most people, even like it. The reason for the emergence of this concept is from a survey conducted in the United States in the 20th century. In 1952, the American Coffee Association and Dr. Lockhart, a professor of chemistry at the Massachusetts Institute of Technology, established a coffee brewing committee (Brewing Committee) to study and promote the coffee industry. Like the fact that "there is 30% soluble matter in a coffee bean" mentioned every day in front of the street, it was published by them in 1957.

Dr Lockhart and his team dissected the structure of coffee beans and found that there was fully 30 per cent of the soluble matter in a single bean, while the remaining 70 per cent was insoluble fiber. The soluble substance of coffee is the substance that can be extracted by water, while the insoluble fiber is simply "coffee grounds", which cannot be melted or extracted, and can only be discarded or used in other ways (such as fertilizer and deodorant). But then they soon discovered that 30% of the soluble matter did not seem to be fully extracted. Under different degrees of extraction, the taste of coffee will change accordingly. So they conducted a special preference survey in which random American passers-by tasted coffee with different levels of extraction and then chose their favorite cup.

After the survey, they immediately integrated the information and found that people preferred coffee with an extraction rate of 17.5% to 21.2% and a concentration of 1.04% to 1.39%. As a result, this coffee parameter, which is most popular with American passers-by, became the original "golden cup criterion". Qianjie now here is a simple science about the extraction rate and concentration: the extraction rate refers to how much soluble matter a coffee bean has been extracted by us, and the concentration refers to the content of coffee in this coffee. But the scope was still too wide, so the committee then resumed the experiment. But this time the survey was aimed at experts in the coffee field, and through more rigorous tasting and research, the gold cup range of coffee was revised: the extraction rate was raised to 18%-22%; the concentration was reduced to 1.15%-1.35%. And this data is the final version. The following picture is the gold cup extraction diagram, which tells us what kind of taste a cup of coffee will taste with different concentrations and extraction rates.

The horizontal axis is the extraction rate, the vertical axis is the concentration, and the diagonal line is the powder-water ratio. The calculation method of the extraction rate of coffee is also very simple, just according to the following formula, you can get the extraction rate of a cup of coffee! (it is worth noting that concentration measurement requires the use of a concentration meter) the extraction rate formula is: coffee liquid weight (ml) ✖️ coffee concentration (TDS) ➗ coffee powder weight (g) We can see that there are many different colors in the picture. Located in the middle of the picture, the darkest color is the range of gold cup extraction. Beyond this range, it will be classified as excessive extraction, with varying degrees of bitterness according to the concentration; below this range, it will be classified as insufficient extraction. There will be different degrees of sour taste depending on the concentration. As a result, many friends will focus on keeping coffee within the range of gold cup extraction. Regardless of the extraction rate or concentration, as long as it is not in the extraction range of this gold cup, they will think that this cup of coffee is not very good.

But! What Qianjie wants to say is that gold cup extraction is just a concept, a standard set by the tastes of a group of people. You know, different countries have different eating habits, and we can't be sure that everyone likes the same standard. Therefore, gold cup extraction can only be used as a reference, we can use it to better understand coffee extraction, but we can not apply this theory to all coffee. The coffee in the golden cup is not necessarily good, and the coffee outside the golden cup is not necessarily bad. As long as the brewed coffee tastes good to us, it is your "golden cup of coffee". Even if it is not within the scope of the golden cup!

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