Many coffee enthusiasts have encountered this confusion: for the same beans, why does the taste always differ between what you brew yourself and what a Front Street barista brews? In fact, this involves two core concepts—extraction yield and concentration (TDS). This article, drawing on the daily experience of FrontStreet Coffee, systematically explains what coffee extraction yield is, how to measure extraction yield with a TDS concentration meter, and the conversion relationships in the SCAA Golden Cup standard among 18%–22% extraction yield, 1.15%–1.35% concentration, and 1:12–1:15 coffee-to-water ratio. The article also reviews the historical origins of the Golden Cup theory, and uses Front Street's brewing of Panama Elida sun-dried Typica as an example, providing complete staged pouring parameters and the extraction yield calculation process, to help you brew a cup of pour-over coffee at home that is not over-extracted and has a pleasing flavor.

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What exactly is coffee extraction yield, and how should it be calculated? This is one of the questions most frequently asked of FrontStreet Coffee baristas in their daily work. Many friends report that when they brew at home and a Front Street barista brews the same bean, the flavors presented are vastly different—what exactly is the reason? Next, Front Street will explain one by one around the definition of extraction yield, the calculation method of extraction yield , and the extraction techniques commonly used by Front Street.

Conceptual analysis of extraction yield

According to the Golden Cup standard given by the SCAA (Specialty Coffee Association of America), the extraction yield should fall within the range of 18%–22%, meaning that out of 10 grams of coffee grounds, 1.8–2.2 grams of substances should be dissolved out; while the TDS concentration of drip coffee is roughly 1.15%–1.35%, that is, the 18%–22% of coffee substances extracted account for 1.15%–1.35% of the entire cup of coffee. FrontStreet Coffee suggests everyone can calculate it themselves: if you want to control the concentration within this range, the ratio of coffee grounds to poured water should roughly be maintained between 1:12 and 1:15.

FrontStreet Coffee uses precisely this range as the basis for formulating brewing parameters. Whenever new beans are launched, they go through repeated adjustments in multiple stages such as roasting, cupping, and pour-over, among which the focus of adjustment in the pour-over stage is observing TDS concentration. Of course, if you are just drinking coffee at home daily, you do not need to specially purchase instruments; judging strength by taste is sufficient.

The origins and development of Golden Cup extraction yield

Concentration and extraction yield are two technical terms, and many baristas still conflate the two, unable to distinguish between them. They are like a pair of brothers, each independent yet inseparable; once you understand this point, it becomes much easier to grasp.

After the end of World War II, the National Coffee Association invited Dr. Ernest Eral Lockhart (1912–2006), a chemistry PhD from MIT, in 1952 to found the Coffee Brewing Institute (1952–1964), responsible for scientific research, promotion, and publishing affairs on filter coffee, and to assist Central and South American coffee-producing countries in selling coffee to the United States.

The team led by Dr. Lockhart conducted a detailed analysis of the structure and components of coffee beans, and found that in roasted beans, the flavor substances soluble in water account for only 28%–30% of the bean weight, with the remaining approximately 70% being insoluble fibrous material. In other words, the extractable portion accounts for at most only 30% of the roasted bean weight. Dr. Lockhart was also the world's first scientist to transform the abstract flavors of coffee into quantified data.

From 1952 to 1960, the National Coffee Association specifically established a Brewing Committee to assist Dr. Lockhart in randomly sampling among the American public, summarizing the public's preference tendencies for coffee strength and the corresponding scientific data. Dr. Lockhart used an electric drip coffee machine to brew coffee from the same origin and the same medium roast level, inviting the public to taste samples with different extraction yields and concentrations, and fill out questionnaires on what they considered the best-tasting and worst-tasting, and researchers then summarized from nearly ten thousand survey results the coffee extraction yield and strength level preferred by the American public.

How to measure concentration with a concentration meter?

The first step is to calibrate the concentration tester, using pure water zeroed as the baseline; then stir the already-extracted pour-over coffee evenly, use a titration tube to draw the coffee liquid, drip it into the coffee concentration tester, press the measurement button, and measure repeatedly several times until the reading stabilizes. Here Front Street lists the calculation formula for coffee extraction yield :

Extraction yield (%) =

Weight of extracted dissolved substances (grams) / Weight of coffee grounds (grams)

According to the definition of concentration, concentration equals the ratio of the weight of extracted substances to the weight of coffee liquid, while extraction yield is the ratio of the weight of extracted substances to the weight of coffee beans. Based on this conversion, extraction yield equals concentration multiplied by the weight of coffee liquid, then divided by the weight of coffee beans.

Front Street here assumes the water absorption rate of coffee grounds is 1:2, so the coffee liquid volume can be roughly calculated as 225－(15×2)=195 grams. Next, Front Street takes Panama Elida as an example to demonstrate how FrontStreet Coffee brews a coffee and calculates whether the extraction yield of this cup meets the standard.

Before brewing a good cup of coffee, there are many factors affecting the result. What we can do is use our professional skills to extract all the beautiful flavors of this bean at this moment. In a cup of coffee, green beans account for 60%, the roaster 30%, and the barista's brewing 10%. It is impossible for the barista's brewing to raise its share to 20%, but as long as it does not lose points and delivers a complete cup of coffee to the customer's hands, that is already enough.

Front Street Panama Elida Estate

Region: Boquete region, Panama

Estate: Elida Estate

Altitude: 1850 meters

Variety: Typica

Processing method: Sun-dried

FrontStreet Coffee brewing parameters:

Water temperature: 90–91°C

Grind size: EK43s grinder setting 10 (fine sugar size)

Coffee-to-water ratio: 1:15

Front Street adopts staged extraction: press the timer, pour in the first stage water at 2 times the coffee dose, i.e., 30 milliliters, pouring in circles over the coffee bed to evenly wet all coffee grounds, and let it bloom until 30 seconds; in the second stage, maintain a thin slow stream pouring in circles up to 125 grams, with pouring taking about 1 minute; when the liquid level drops to 2/3 of the coffee bed, begin the third stage, also with a thin slow stream pouring in circles up to 225 milliliters, with the stop-pouring time at about 1 minute 45 seconds to 1 minute 50 seconds, and total extraction time about 2 minutes.

Then calibrate the concentration meter, shake the coffee liquid in the server evenly, use a dropper to draw coffee liquid and drip it onto the concentration meter; at this point the concentration meter shows the coffee concentration is 1.34%.

Then the extraction yield is 17.42%.

That is to say, this cup of pour-over Elida has a concentration of 1.34% and an extraction yield of 17.42%. Although this Front Street brewing of Panama Elida is slightly insufficient, it did not affect the overall expression of the coffee's flavor. The wet aroma of this Panama Elida carries fermented notes of peach and raisin along with orange tonality; as the temperature slowly drops, the sweetness of sucrose and melon gradually emerges, and the finish carries the tea-like sensation of grapefruit and green tea.

In Front Street's view, Golden Cup extraction has indicative symbolic significance for the entire coffee industry. Because Golden Cup extraction standardizes coffee extraction theory in a scientific way, becoming a globally universal reference template. Front Street's current coffee experiments and offerings are all developed based on Golden Cup theory, but it is ultimately only a reference and does not represent absolute correctness. Front Street believes that even if the coffee you brew already falls within the Golden Cup range, if the taste and flavor are not pleasing, you do not have to rigidly adhere to theory; being able to let customers drink coffee they like at Front Street is already enough.

The above content is compiled by CoffeeHunters, a coffee news website.