Introduction:The flavor variations in pour over coffee can often be confusing, but the key lies in the precise control of extraction yield and concentration. This article delves into the Golden Cup standard’s ideal extraction range of 18%–22% and concentration range of 1.15%–1.35%, explaining the scientific rationale behind the commonly recommended brew ratio of 1:12 to 1:15. Through practical examples, it demonstrates how to calculate extraction yield, adjust pouring parameters, avoid over-extraction, and help you brew balanced pour over coffee at home.
Many coffee enthusiasts have this question: why does the same coffee bean taste different when brewed by themselves compared to when made by a barista? The answer often lies in two key metrics—extraction yield and concentration. These two figures directly affect the taste and flavor profile of the coffee and are also the core basis for professional baristas when adjusting brewing parameters.
According to the Golden Cup Standard established by the Specialty Coffee Association of America (SCAA), the ideal coffee extraction yield should fall between 18% and 22%. This means that out of every 10 grams of coffee grounds, approximately 1.8 to 2.2 grams of coffee substances are dissolved. At the same time, the proportion of these extracted substances in the final brewed coffee liquid (i.e., TDS concentration) should be maintained within the range of 1.15% to 1.35%. Combining these two indicators, a generally recommended brew ratio is 1:12 to 1:15, meaning 1 gram of coffee grounds to 12 to 15 milliliters of water.
So, what exactly is extraction yield? Simply put, it refers to the percentage of substances dissolved from the coffee grounds relative to the total weight of the coffee grounds. For example, if you use 15 grams of coffee grounds and the final dissolved substances amount to 2.7 grams, then the extraction yield of that cup of coffee is 2.7 divided by 15, equaling 18%. As for concentration, it refers to the proportion of these dissolved substances in the entire cup of coffee liquid. For instance, if a 225-milliliter cup of coffee contains 2.7 grams of extracted substances, then its concentration is 2.7 divided by 225, multiplied by 100%, which is approximately 1.2%.
To measure the concentration of coffee, a specialized TDS concentration meter can be used. When operating, first calibrate the instrument with pure water to reset the reading to zero. Then, thoroughly stir the brewed coffee and use a pipette or burette to draw an appropriate amount of coffee liquid into the instrument. Press the measurement button, repeat several times until the reading stabilizes. This value is the TDS concentration of the coffee. By combining the concentration with the total weight of the coffee liquid, the extraction yield can be further calculated.
The origin of the Golden Cup theory can be traced back to the post-World War II era. In 1952, the National Coffee Association of the United States invited Dr. Ernest Eral Lockhart, a chemistry Ph.D. from MIT, to establish the Coffee Brewing Institute, dedicated to the scientific research and promotion of filter coffee. Dr. Lockhart and his team found that only about 28% to 30% of substances in roasted coffee beans can be dissolved by water, with the remaining approximately 70% being indissoluble fibrous matter. In other words, the truly flavorful and extractable substances in coffee beans account for only about 30% of the bean’s weight at most.
Between 1952 and 1960, the institute conducted extensive surveys and summarized the preferred coffee concentration and extraction rate ranges among American consumers. Researchers had participants taste coffees with varying extraction rates and concentrations and fill out preference questionnaires. Ultimately, they concluded that an extraction rate of 18%–22% and a concentration of 1.15%–1.35% were acceptable to most people, forming an important basis for the later Golden Cup Standard.
Measuring coffee concentration accurately at home is not complicated. First, ensure the concentration meter has been calibrated with pure water. Then, thoroughly shake the brewed coffee liquid and use a pipette to draw an appropriate amount of coffee into the instrument’s detection port. Press the measurement button, and repeat the measurement until the reading stabilizes. It’s important to note that during the brewing process, coffee grounds absorb water and expand, typically at a water absorption rate of about 1:2—meaning 15 grams of coffee grounds will absorb approximately 30 milliliters of water. Therefore, the actual volume of coffee liquid needs to subtract this absorbed water from the total water poured. For example, if 225 milliliters of water is poured and 30 milliliters are absorbed, the resulting coffee liquid volume would be about 195 milliliters.
Next, let’s take a Panamanian Elida Natural Typica as an example to see how to control brew ratio and extraction parameters in actual brewing. This coffee bean is from the Boquete region of Panama, grown at an altitude of 1850 meters, using the natural processing method. Its flavors include fermented notes of peach, raisin, and orange, with sweet sensations of cane sugar and melon at medium to low temperatures, and a clean finish of grapefruit and green tea.
The brewing parameters are set as follows: water temperature at 90–91°C, grind size adjusted to that of fine sugar (such as EK43s grinder setting at 10), and a brew ratio of 1:15. The brewing process is divided into three pours: first, after starting the timer, pour 30 milliliters of water (about twice the coffee dose), evenly circling to wet all the coffee grounds, allowing for a 30-second bloom; next, slowly pour with a thin stream in a circular motion up to 125 grams, taking about 1 minute; finally, when the liquid level drops to two-thirds of the coffee bed, continue pouring with a thin stream up to 225 milliliters, with the total extraction time controlled between 1 minute 45 seconds and 1 minute 50 seconds, for an overall duration of about 2 minutes.
After brewing, shake the coffee liquid and use the concentration meter to measure, showing a TDS concentration of 1.34%. Based on the formula calculation, the extraction yield of this cup of coffee is 17.42%, slightly below the Golden Cup standard range of 18%–22%, but the overall flavor performance remains balanced. This shows that even if the extraction yield does not fully fall within the ideal range, as long as the concentration is moderate, you can still brew a pour over coffee with pleasing flavors.
The Golden Cup theory provides a scientific reference framework for coffee brewing, but it is not an absolute standard. Each coffee enthusiast has different taste preferences, and actual brewing still requires flexible adjustments based on bean characteristics, grind size, and water temperature. Remember, the goal of brewing is to showcase the inherent beautiful flavors of the coffee as much as possible, rather than blindly pursuing theoretical numbers. Through continuous experimentation and adjustment, you will surely find the brewing method that suits you best.
The above content is compiled by CoffeeHunters, a coffee news website.
