Golden Cup Coffee Extraction Rate and Concentration Calculation Formula: What are the Golden Cup Extraction Criteria and Standards?

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In real coffee extraction, to pursue better coffee taste, one must strive to preserve the original flavor while avoiding unpleasant flavors. The balance between these involves several widely recognized standards—this is the legendary Golden Cup standard. In coffee, standards are very important; they act like a circle or a line, providing beginners with a reference benchmark. However, what's more important than the standard itself is continuous experimentation and exploration based on those standards to find the Golden Cup standard that suits oneself and consumers.

American Specialty Coffee Association (SCAA)

Extraction Rate [18%-22%] Concentration [1.15%-1.35%]

European Specialty Coffee Association (SCAE)

Extraction Rate [18%-22%] Concentration [1.2%-1.45%]

Norwegian Coffee Association (NCA)

Extraction Rate [18%-22%] Concentration [1.3%-1.55%]

Brazilian Coffee Association (ABIC)

Extraction Rate [18%-22%] Concentration [2%-2.4%]

[Concentration] represents the proportion of "extracted coffee substances" in the total coffee liquid.

[Extraction Rate] represents the proportion of "extracted coffee substances" to the total coffee bean weight.

Under-extraction means the extraction rate is below 18%, while over-extraction means the extraction rate exceeds 22%.

FrontStreet Coffee uses these ranges to standardize our brewing parameters. Each time new beans are launched, they undergo adjustments in roasting, cupping, and pour-over processes. The adjustment direction for pour-overs is determined by TDS concentration readings. Of course, for regular home coffee drinking, there's no need to buy specialized instruments—judging concentration by taste is sufficient.

The Origin of Golden Cup Extraction

Coffee concentration and extraction rate are two technical terms that most baristas still confuse, not clearly distinguishing between them. The two are like the Haier brothers—independent individuals who cannot be separated from each other. Understanding this relationship makes comprehension much easier.

After World War II, the National Coffee Association hired MIT chemistry Ph.D. Dr. Ernest Eral Lockhart (1912-2006) in 1952 to establish the Coffee Brewing Institute (1952-1964), responsible for scientific research, promotion, and publication of drip coffee, while assisting Central and South American coffee-producing countries in selling coffee to the United States.

The team led by Dr. Lockhart conducted detailed analysis of coffee bean structure and composition, discovering that water-soluble flavor compounds extractable from roasted coffee beans only account for 28%-30% of the roasted bean weight, while the remaining 70% consists of insoluble fiber. The extractable substances constitute only 30% of the roasted coffee bean weight. Dr. Lockhart was the first scientist in the world to quantify abstract coffee flavors into data.

From 1952 to 1960, the National Coffee Association specially established a Brewing Committee to assist Dr. Lockhart in random sampling of American consumers, summarizing American preferences for coffee concentration and scientific data.

Dr. Lockhart used electric drip coffee machines to brew medium-roasted coffee from the same origin with different extraction rates and concentrations, inviting people to taste and complete questionnaires about what they considered the best and worst tasting. Researchers then summarized nearly ten thousand surveys to determine American consumers' preferred coffee extraction rate and concentration.

Preliminary research results showed that American consumers preferred coffee extraction rates between 17.5%-21.2% and concentration ranges between 1.04%-1.39%. This was the initial "Golden Cup Standard."

Test subjects found that the extraction range of 17.5%-21.2% presented the most balanced and pleasant combination of sour, sweet, bitter, and salty tastes in terms of mouthfeel and aroma. Below 17.5% was considered under-extraction, while above 21.2% was over-extraction. For coffee concentration, below 1.04% was perceived as too weak and bland, while above 1.39% was considered too strong and harsh.

The CBI led by Dr. Lockhart was upgraded to the Coffee Brewing Center (CBC) in 1964 to strengthen various research programs and promotional efforts. For thoroughness, they collaborated with the U.S. military's renowned Midwest Research Center to review the initial data.

After careful deliberation and expert cupping, the initial extraction rate range was adjusted upward to 18%-22%, and the concentration range was modified to 1.15%-1.35%. The Specialty Coffee Association of America (SCAA) adopted this revised version and continues to use it today. Now, the SCAA and SCAE have merged into the Specialty Coffee Association (SCA).

Concentration and Extraction Rate Calculation Methods

Concentration (%): Weight of extracted coffee substances (g) ÷ Coffee liquid volume (ml)

Concentration represents the intensity of coffee's sour, sweet, bitter, and salty taste "quantity." For drip coffee, concentrations below 1.15% (11,500 ppm) have very weak, watery flavors; concentrations above 1.55% (15,500 ppm) are considered too strong for most people to drink comfortably.

Extraction Rate (%): Weight of extracted coffee substances (g) ÷ Coffee powder weight (g)

Extraction rate represents the "quality" of coffee's sour, sweet, bitter, and salty tastes. Extraction exceeding 22% tends to produce bitter and harsh flavors; extraction below 18% tends to produce flat, sharp acidity and green flavors (commonly known as grassy taste).

Explanation: The weight of extracted coffee substances (g) is the weight of flavor compounds extracted from the coffee grounds. For example:

15g coffee grounds

Powder to water ratio 1:16

Brewed coffee liquid is 216ml

ExtractMoJo (VST) concentration 1.31%

Concentration 1.31% = Weight of extracted coffee substances ÷ 216ml

Weight of extracted coffee substances = 2.8g

Extraction Rate = Weight of extracted coffee substances ÷ Coffee powder amount

Extraction Rate = 2.8g ÷ 15g = 18.6%

This is the formula for calculating extraction rate based on coffee liquid volume in milliliters. There's also a formula based on coffee liquid weight in grams, which is comparatively simpler to calculate. The values obtained from both methods have minimal error and are very close. Today we've covered this first formula (don't hit me!). We can discuss this further.

ExtractMoJo Golden Cup Analyzer

The magical ExtractMoJo analyzer was invented in 2008 by Vince Fedele, president of American VST company. Simply by dropping 2-3 milliliters of cooled coffee liquid onto the optical instrument, one can accurately read the coffee concentration value—very convenient. This eliminates the need for the previous method of drying coffee liquid or coffee grounds in an oven, avoiding complicated coffee concentration calculations.

(ExtractMoJo, VST concentration analyzer)

Without VST as an auxiliary measuring device, calculating extraction rates is much more tedious. Initially, Dr. Lockhart used the simplest primitive method, brewing coffee with an American coffee machine, noting the milliliter amount of black coffee, then pouring it into a metal container, placing it in an oven to completely dry the water content, leaving only solid powder in the container—these were the extracted coffee solid flavor compounds (hot water soluble substances). The weight of soluble substances divided by the weight of coffee grounds used yielded the extraction rate.

Concentration Calculation Formula

Weight of extracted coffee substances = Weight of coffee grounds before brewing - Weight of coffee grounds after drying

Extraction Rate % = (Weight of coffee grounds before brewing - Weight of dried coffee grounds after brewing) ÷ Weight of coffee grounds before brewing

Concentration % = Weight of extracted coffee substances ÷ Coffee liquid milliliters

Assuming:

15g coffee grounds

12.17g coffee grounds after drying

Powder to water ratio 1:16

Brewed coffee liquid is 216ml

Extraction Rate % = (15-12.17) ÷ 15

= 2.83g ÷ 15

= 18.8%

Concentration % = Weight of extracted coffee substances ÷ Coffee liquid milliliters

= 2.83g ÷ 216ml

= 1.31%

Note: Collect all the wet coffee grounds after brewing, place them in an oven to dry, then measure with an electronic scale to calculate the soluble coffee substances. If you don't have an oven, you can also dry them in direct sunlight, but be careful not to let the wind blow away the coffee grounds, which would affect accuracy. The dried coffee grounds should have the same dryness as the pre-brewing coffee grounds—fluffy and non-sticky to the touch.

Before brewing a good cup of coffee, there are many determining factors. What we can control is using our professional skills to extract all the good flavors that exist in this cup of coffee. For a cup of coffee, green beans determine 60%, the roaster determines 30%, and the barista's brewing determines 10%. The barista's brewing cannot add up to 20%, but as long as we don't detract from the quality, presenting a complete cup of coffee to the guest is sufficient.

Today, we'll demonstrate using FrontStreet Coffee's Ethiopia Flower Queen 4.0. We need to prepare the following items: pour-over coffee equipment, coffee concentration tester (ExtractMoJo), titration tube, and clean water.

Coffee Origin: Ethiopia, Sidamo, Guji Zone

Processing Station: Buku Processing Station

Altitude: 2250-2350 meters

Processing Method: Natural processing

Coffee Varieties: Local indigenous varieties

Brewing Plan

Powder amount: 15g

Powder to water ratio: 1:15

Grind size: Fine grind (80% pass-through rate with #20 standard sieve)

Water temperature: 91°C

Dripper: V60

Brewing Process

First segment: Pour 30g of water for 30-second bloom.

Second segment: Pour 95g (electronic scale shows around 125g), completed in about 1 minute, with a 10-second interval.

Third segment: Pour the remaining 100g (electronic scale shows around 225g), completed in about 1 minute 40 seconds.

Drip filtration completes in about 2 minutes. Remove the dripper to complete extraction.

How to Measure Concentration?

First, calibrate the concentration tester using pure water to zero the standard. Then stir the completed pour-over coffee and extract coffee liquid using a titration tube, place it in the coffee concentration tester, press the measure button, and take multiple readings until the value stabilizes.

How to Calculate Extraction Rate?

From the concentration definition, we know that concentration equals the ratio of extracted substance weight to coffee liquid, and extraction rate equals the ratio of extracted substance weight to coffee bean weight.

Converting the formula, we get that extraction rate equals the product of concentration and coffee liquid weight, divided by coffee bean weight.

Here we generally assume the coffee grounds' water absorption rate is 1:2, so we roughly calculate the coffee liquid amount as 225 - (15 × 2) = 195g.

We measured a concentration of 1.45%

The extraction rate is therefore 1.45% × 195 ÷ 15 = 18.85%

We can conclude that this is a pour-over coffee with 1.45% concentration and 18.85% extraction rate.

We can determine this is a pour-over coffee with slightly high concentration and appropriate extraction rate. We can use this data to adjust the coffee through ratios and other factors.

Of course, the Golden Cup is just a reference system. Everyone's taste is different, and pour-over coffee that meets Golden Cup data doesn't necessarily represent delicious coffee. Therefore, trying more and tasting more is still the recommended approach.

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