How to Calculate Coffee Strength and Extraction Rate? What Does Golden Cup Extraction Mean?

Understanding Gold Cup Extraction

FrontStreet Coffee often references the concept of "Gold Cup Extraction" in our articles. This is a result derived from research initiated by the Specialty Coffee Association of America (SCAA), which identified an "optimal" extraction range for coffee by quantifying extraction yield and concentration. When both numerical values of brewed coffee fall within this range, the coffee will likely taste good.

However, as nothing is absolute, since the participants and coffee beans in the Gold Cup experiments were limited, this result doesn't necessarily mean all delicious coffee conforms to the Gold Cup concept. Coffee within the Gold Cup extraction range isn't necessarily good, and coffee outside this range isn't necessarily bad. Nevertheless, it can serve as a reference to assist in making delicious coffee. After all, with extraction yield and concentration quantified, we can more intuitively see the "state" of the coffee itself. When we feel that brewed coffee isn't quite right but aren't sure what's wrong, we can verify our thoughts by measuring extraction yield and concentration, then find reasonable adjustment solutions.

Measuring Coffee Extraction Yield and Concentration

So today, FrontStreet Coffee will share how to measure coffee extraction yield and concentration. First, let's briefly understand what coffee extraction yield and concentration are respectively!

Coffee Extraction Yield

So-called coffee extraction yield refers to the proportion of coffee substances extracted from coffee beans/grounds. Only 30% of substances from a coffee bean can dissolve, so the maximum extraction yield of a coffee bean is only 30%, with the remaining 70% being insoluble woody fiber—the coffee grounds left in the filter after brewing is complete.

In the Gold Cup extraction concept, the ideal extraction yield is in the 18%-22% range. Coffee with extraction yield higher than this range may have noticeable bitterness and mixed flavors due to excessive dissolved substances; while coffee below this range may show under-extracted flavor characteristics like sharp acidity and grassy notes due to insufficient dissolved substances (not absolute).

Coffee Concentration

Coffee concentration refers to the proportion of coffee substances in our brewed coffee liquid. The higher the concentration, the higher the proportion of coffee substances in the coffee, and vice versa.

In the Gold Cup extraction concept, the ideal concentration value is in the 1.15%-1.45% range. Coffee with concentration below this range will taste bland and thin; while coffee above this range will have overly concentrated flavors, resulting in unclear flavor profiles.

How to Calculate Coffee Extraction Yield and Concentration?

To summarize, extraction yield represents "the proportion of coffee substances extracted from coffee beans," while concentration represents "the proportion of extracted coffee substances to total coffee liquid."

The calculation formula for coffee concentration is: weight of extracted coffee substances ÷ weight of coffee liquid. The calculation formula for coffee extraction yield is: weight of coffee substances ÷ weight of coffee beans (grounds). If combined, the extraction yield calculation formula can be: coffee extraction yield = coffee liquid concentration × coffee liquid weight ÷ coffee bean (grounds) weight.

This means that to calculate coffee extraction yield, we first need to measure coffee concentration. Then calculate extraction yield based on the formula. So how do we measure coffee concentration? There are two methods!

Methods for Measuring Coffee Concentration

1. Using a TDS Water Quality Pen

TDS (Total Dissolved Solids) water quality pens are commonly used tools for measuring water quality, and they can also be used to measure coffee concentration. Because their measurement principle indirectly estimates TDS values by measuring the electrical conductivity in liquids, and most dissolved substances in water increase water conductivity, coffee can also be measured using TDS for concentration. Most importantly, compared to another method, TDS measurement pens are much, much lower in cost!

But the disadvantages are also obvious—it cannot calculate very precise results. Because not all substances increase water conductivity, it can only measure approximate values with slight errors.

2. Using a Coffee Concentration Meter

If we want to obtain more precise measurement results, we need to use a coffee concentration meter. Its principle for measuring coffee concentration is to determine coffee concentration by measuring the refractive index of dissolved solids in coffee liquid. The advantages are straightforward: fast and accurate. Measurement speed is quick, results are relatively more precise and intuitive. However, it has one major disadvantage: expensive!

Coffee concentration meters start at 2k, which is very unfriendly to the wallet. So if you're just planning to measure for fun, using a measurement pen is completely sufficient, as this isn't necessarily a must-do thing~

Demonstration: Measuring Coffee Concentration and Calculating Extraction Yield

Next, FrontStreet Coffee will demonstrate how to use both methods to measure coffee concentration and calculate extraction yield. First, let's brew any coffee. Since FrontStreet Coffee is demonstrating concentration and extraction yield calculations today, we'll skip the brewing details—parameters are the same as usual, still using 15g of grounds with a 1:15 coffee-to-water ratio.

After brewing is complete, we first weigh the coffee liquid.

The coffee beans FrontStreet Coffee used today are Santa Vani, a light-roast coffee bean processed with anaerobic natural method. The amount of water poured is 224ml, with final liquid weight at 194ml, meaning 30ml was absorbed by the coffee grounds. Then, we use both the measurement pen and concentration meter to measure the coffee liquid concentration. The measurement pen can be inserted directly into the coffee liquid, while the concentration meter requires us to use a dropper or small spoon to place coffee liquid onto the meter's measuring prism, then press the switch to measure.

The result from the measurement pen is 143×10ppm. Because the pen uses ppm rather than percentage calculation, we need to divide by 1000 for conversion, which comes to approximately 1.43% concentration. The result from the concentration meter is 1.47% (because it's affected by temperature, we should take multiple measurements).

Now that we know the coffee concentration, we can calculate the extraction yield. According to the formula "coffee extraction yield = coffee liquid concentration × coffee liquid weight ÷ coffee bean (grounds) weight," our calculation is: 1.47% (concentration meter result) × 194 ÷ 15, giving an extraction yield of approximately 19.01%.

Once we understand how to calculate extraction yield and concentration, we can use measurements to verify our thoughts next time we find coffee taste slightly off but aren't sure why. We can see whether it's due to excessive dissolution causing mixed flavors in coffee, or insufficient dissolution leading to unclear coffee taste~

- END -

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473