Coffee Golden Cup Extraction Theory: How to Calculate Pour-Over Coffee Extraction Rate and Concentration - Pour-Over Coffee Powder-to-Water Ratio Recommendations

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The Case of the TDS Meter Incident

Recently, in an article where a barista was venting, there was a case mentioned:

"I'd like a pour-over Guodingding coffee."

(After the barista finished the extraction, the customer took out a TDS concentration meter, and without tasting, directly scooped a little to test the concentration)

"Your coffee's concentration is 1.37%! It's already exceeded the 1.15%-1.35% range in SCA's Golden Cup extraction standards!"

"I'm sorry, why don't you take a sip first, and if you feel it's not right, I'll make another cup for you~"

"No need! You're just unprofessional! Take this cup away, I'm not coming back!"

"……………………………………………………………………………………"

The Evolution of Golden Cup Standards

Regarding the optimal values for Golden Cup extraction, I believe many people have received information like this: the ideal concentration for a cup of coffee is 1.15%-1.35%, with an ideal extraction rate of 18%-22%. But in reality, this is not SCA's ideal concentration, but rather SCAA's (Specialty Coffee Association of America) ideal concentration.

Although the ideal extraction rate of Golden Cup theory is globally standardized at 18%-22%, there are disagreements among European and American coffee associations regarding the ideal concentration range. SCAA's ideal concentration is 1.15%-1.35%, SCAE's (Specialty Coffee Association of Europe) ideal concentration is 1.2%-1.45%, and NCA's (National Coffee Association of America) ideal concentration is 1.3%-1.55%.

However, such ideal concentration ranges are based on Dr. Lockhart's research in the 1950s-60s, which established Total Dissolved Solids (TDS) and extraction rate as quantitative standards for measuring coffee quality. He collaborated with several research institutions to create a coffee brewing control chart, which became the textbook for coffee extraction and Golden Cup theory for the following decades.

The Revised Golden Cup Standards

But with continuous changes in coffee quality, roasting preferences, and other factors, some content in the original Golden Cup extraction theory couldn't keep up with the advances in modern equipment, diverse extraction techniques, and flavor perception. Therefore, after SCAA and SCAE merged to form SCA in 2017, they collaborated with the Coffee Center at the University of California, Davis to adjust the coffee brewing control chart, and released a slightly modified version in 2019.

The biggest difference between the two brewing control charts is: coffee outside the ideal Golden Cup theory values might also taste good! After the adjustment, the upper limit of ideal concentration was expanded from 1.35% to 1.45%; the recommended brewing ratio was also expanded from the original 1:15-1:20 to 1:14-1:20; the tolerable upper concentration limit was also raised from 1.6% to 1.8%. The definition of "bitterness" was also changed to over-extraction.

The revised chart can improve the situation where sensory descriptions and coffee consumer preferences are confused. To put it simply, the old chart's explanation of concentration was somewhat dogmatic. For example, when people tasted a coffee with higher bitterness (regardless of whether the taster accepted these bitterness notes), once it exceeded the ideal concentration, it was directly defined as unpleasant bitterness.

Another situation is like the case at the beginning of the article - the difference between 1.35% and 1.37%. Can our senses really distinguish this difference? But due to the limitations of the published chart, even if our senses don't perceive a difference, it would be directly stated that this is a coffee with non-ideal/poor concentration, ignoring what the senses actually feel, which is unfair to the judgment of the coffee.

Beyond Simple Measurements

Although the chart has been adjusted, some problems remain unresolved - when discussing whether coffee tastes good, people often only talk about concentration without mentioning extraction rate. When coffee doesn't taste good, the first thought is "it's too strong!" Or they only talk about extraction rate without mentioning concentration, for example, "it's over-extracted!"

In subsequent SCA research, it was found that different flavor expressions in coffee require deviation from ideal ranges to be properly showcased. Today's coffee flavors are increasingly diverse, and strictly adhering to ideal extraction rates and concentrations during brewing doesn't necessarily result in the best coffee flavor expression.

According to joint research and analysis by the Coffee Center and SCA, the unique flavors in differently roasted coffee beans require extraction rates and concentrations below or above ideal ranges to be properly expressed.

Sourness, citrus, and dried fruit flavors often appear in situations of high concentration and low extraction. The intensity of sourness and citrus usually increases with concentration but decreases with extraction rate. Appropriate high concentration and low extraction can enhance the pleasant acidity in coffee; excessive high concentration and low extraction can lead to unpleasant sharp acidity. Tea-like, floral, and chocolate flavors often appear in situations of low concentration and high extraction, while sweetness often appears in low concentration and low extraction.

But in both the original and revised versions, regardless of the situation, high concentration means strong, and low concentration means weak. However, some delightful flavors are best expressed at low concentrations, yet the charts uniformly label them as "weak." Therefore, teacher Han Huaizong stated in his "Fourth Wave Coffee Science" that both charts may be misleading.

The Purpose of Coffee

The Golden Cup extraction standards are just reference standards set by the specialty coffee industry to reduce disputes caused by individual differences in judging coffee concentration. They are not 100% requirements that coffee must be within standard values to taste good, or that coffee will taste bad if TDS is higher/lower.

The meaning of drinking coffee should be to make yourself feel happy, pleasant, and comfortable. As long as you like drinking it, that's what matters~ Even if the concentration shown by the TDS meter is not within the ideal range of Golden Cup theory, as long as you think it tastes good, then it's good! Don't make drinking coffee like a chemistry class; it doesn't require carefully pursuing precise values~

Image source: Internet

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