How to calculate the concentration and extraction rate of coffee? What does coffee cup extract mean?

Qianjie often quotes the concept of "Golden Cup extraction" (Gold Cup Extraction) in his articles, which is the result of a survey conducted by the American Fine Coffee Association (SCAA). By quantifying the extraction rate and concentration, we can find an "optimal" extraction range of coffee. As long as the two values of the brewed coffee are in the range, there is a good chance that this cup of coffee will be delicious.

However, as the saying goes, there is no certainty, and due to the restrictions on the masses and coffee beans who participated in the golden cup experiment, this result does not mean that all tasty coffee conforms to the golden cup concept. The coffee within the gold cup extraction range is not necessarily delicious, and the coffee outside the gold cup extraction range is not necessarily bad. However, it can be used as a reference to assist in the production of good coffee. After all, the extraction rate and concentration are quantified, and we can see the "state" of the coffee itself more intuitively. When we feel that the coffee is not good enough but do not know what went wrong, we can verify the idea by measuring the extraction rate and concentration, and then find a reasonable adjustment plan.

So today, Qianjie is going to share how the extraction rate and concentration of coffee should be measured. So first of all, let's have a brief understanding of the extraction rate and concentration of coffee.

Coffee extraction rate the so-called coffee extraction rate refers to the proportion of coffee substances extracted from coffee beans / powder. Only 30% of the substance can be dissolved in a coffee bean, so the maximum extraction rate of a coffee bean is only 30%, and the remaining 70% are insoluble wood fibers, that is, coffee grounds left in the bowl after brewing.

The ideal extraction rate in the concept of gold cup extraction is in the range of 18% to 22%. Coffee with an extraction rate higher than this range will have a probability of drinking bitterness and miscellaneous taste because there are too many dissolved substances, while coffee below this range is likely to have underextracted flavors such as acidity and weeds (not absolute).

The concentration of coffee refers to the proportion of coffee substances that we brew out of the water. The higher the concentration, the higher the proportion of coffee substances in coffee, and vice versa.

The ideal concentration in the concept of gold cup extraction is in the range of 1.15% to 1.45%. Coffee with a concentration below this range will have a light taste and a thin taste, while coffee with a concentration higher than this range will be too concentrated, resulting in unclear flavor.

How to calculate the extraction rate and concentration of coffee? To sum up, we can know that the extraction rate represents "the percentage of coffee substances extracted from coffee beans", while the concentration represents "the proportion of coffee substances extracted to the total coffee liquid".

Then, the formula for calculating the coffee concentration is: the weight of the extracted coffee substance / the weight of the coffee solution, the formula for calculating the extraction rate of coffee is: the weight of the coffee substance / the weight of the coffee bean (powder). Then the formula for calculating the extraction rate can be: coffee extraction rate = coffee solution concentration × coffee liquid weight / coffee bean (powder) weight, that is to say, if you want to calculate the coffee extraction rate. Then we need to measure the concentration of coffee first. Then the extraction rate of coffee is calculated according to the formula. So how to measure the concentration of coffee? There are two ways!

1. Using TDS water quality detection pen to measure TDS (Total Dissolved Solids) water quality detection pen is a commonly used prop for measuring water quality, and it can also be used to measure the concentration of coffee. Because its measurement principle is to indirectly estimate the TDs value by measuring the electrical conductivity of the liquid, and most substances dissolved in water will increase the electrical conductivity of the water, coffee can also use TDS to measure the concentration. And the most important thing is that compared with the other way, the cost of TDS measuring pen will be much lower!

But the disadvantage is also obvious, that is, it can not calculate very fine results. Because not all substances can increase the electrical conductivity of water, so it can only measure an approximate, there will be a little error.

Using a coffee concentration meter to measure if we want to get more accurate results, we need a coffee concentration meter. The principle of measuring the concentration of coffee is to determine the concentration of coffee by measuring the refractive index of dissolved solids in the coffee liquid. The advantage is that it is fast and accurate. The measurement speed is very fast, and the results are relatively more accurate and intuitive. Is that it has a very big disadvantage: expensive!

The coffee concentration meter starts at 2k, which is a very unfriendly price for wallets. So if you are just going to test and play, then in fact, it is enough to use a measuring pen, after all, this is not a very necessary thing ~ then the front street will demonstrate how to use both to measure the concentration of coffee and to calculate the extraction rate. First of all, let's brew out a pot of arbitrary coffee. The front street is to demonstrate the concentration and extraction rate of the calculation, so directly skip the cooking, the parameters are the same as usual, is still the use of 15g powder, 1:15 powder ratio. Then when we have finished brewing, let's weigh the coffee liquid first.

The coffee bean used in front street is Santa Vini, which is a light roasted coffee bean treated by anaerobic sun treatment. The amount of water injected is 224ml, and the final liquid weight is in 194ml, which is absorbed by 30ml by coffee powder. Then, we use the measuring pen and the concentration meter to measure the concentration of the coffee liquid. The measuring pen can be put directly into the coffee liquid, while the concentration meter measurement requires us to use a straw or spoon to scoop the coffee liquid onto the measuring prism of the concentration meter, and then press the switch to measure.

The result of the measuring pen is 143x 10ppm, because the measuring pen is calculated not by percentage but by ppm, so we need to divide by 1000, which translates to a concentration of about 1.43%. The result of the measuring instrument is 1.47% (because of the temperature, we'd better make multiple measurements).

So, we know the concentration of coffee, and then we can calculate the extraction rate of coffee. According to the formula of "coffee extraction rate = coffee liquid concentration × coffee liquid weight / coffee bean (powder) weight", our calculation is 1.47% (the result of the concentration meter) × 194 / 15, and the extraction rate is about 19.01%. When we know how the extraction rate and concentration are calculated, we can test the idea the next time we find something wrong but uncertain about the taste of the coffee. Let's see if the coffee tastes bad because it dissolves too much, or it doesn't taste obvious because it dissolves too little.

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