What Are the Standards for Golden Cup Extraction? How Should Coffee Extraction Yield and Concentration Be Calculated?

What is Golden Cup Extraction?

"Golden Cup Extraction" is a concept frequently mentioned in the world of pour-over coffee. Many coffee brewing tutorials often reference this term. Most beginners may find it unfamiliar, often encountering confusing numbers and diagrams when searching online. That's why FrontStreet Coffee will guide you through understanding what Golden Cup Extraction is today!

The Origin of Golden Cup Extraction

Golden Cup Extraction, as FrontStreet Coffee mentioned earlier, is a concept that conveys that coffee has a most desirable extraction range. As long as our brewed coffee falls within this range, its flavor will be acceptable and even enjoyable to the vast majority of people. This concept originated from a research study conducted in the United States in the twentieth century. In 1952, the American Coffee Association, together with Dr. Lockhart (a chemistry professor at MIT), established a Coffee Brewing Committee. This committee aimed to research and promote the coffee industry. The fact that FrontStreet Coffee often mentions that "one coffee bean contains 30% soluble substances" was published by them in 1957.

The Science Behind Coffee Extraction

Dr. Lockhart and his team analyzed the structure of coffee beans and discovered that a single coffee bean contains 30% soluble substances, while the remaining 70% consists of insoluble fiber materials. The soluble substances in coffee are what can be extracted by water, while the insoluble fiber materials are essentially "coffee grounds" that cannot dissolve or be extracted, ultimately needing to be discarded or used for other purposes (such as fertilizer or deodorizer). However, they quickly discovered that not all 30% of these soluble substances should be completely extracted. Under different extraction levels, the flavor of coffee changes accordingly. Therefore, they conducted a special preference survey, giving random American passersby coffee brewed to different extraction levels to select their favorite cup.

Defining the Golden Cup Standard

After the survey, they immediately compiled the information and found that people preferred coffee with an extraction rate between 17.5%-21.2% and a concentration between 1.04%-1.39%. Thus, these coffee parameters most favored by American passersby became the initial "Golden Cup Standard." FrontStreet Coffee will now briefly explain extraction rate and concentration: The extraction rate refers to how much soluble substance has been extracted from a coffee bean, while concentration refers to the amount of coffee substances in the brewed coffee. However, this range was still too broad, so the committee later reinitiated the experiment. This time, the survey subjects were coffee industry experts. Through more rigorous tasting and research, the Golden Cup range for coffee was eventually modified: extraction rate adjusted to 18%-22%, and concentration reduced to the range of 1.15%-1.35%. This data represents the final version. The following diagram is the Golden Cup Extraction chart, which shows us what flavors result from different combinations of concentration and extraction rates in coffee.

Understanding the Extraction Chart

The horizontal axis represents extraction rate, the vertical axis represents concentration, and the diagonal lines represent the coffee-to-water ratio. The calculation method for coffee extraction rate is also simple - just use the formula below to calculate a cup of coffee's extraction rate! (It's worth noting that concentration measurement requires a refractometer.) The extraction rate formula is: Coffee liquid weight (ml) ✖️ Coffee concentration (TDS) ➗ Coffee grounds weight (g). We can see many different colored blocks in the image. Located in the center of the chart, the darkest colored area represents the Golden Cup Extraction range. Beyond this range, coffee is classified as over-extracted, with varying degrees of bitterness depending on concentration. Below this range, coffee is classified as under-extracted, with varying degrees of sourness depending on concentration. Therefore, many enthusiasts focus on keeping their coffee within the Golden Cup Extraction range. Whether in terms of extraction rate or concentration, if they fall outside this Golden Cup range, they consider the coffee less enjoyable.

The Personal Nature of Coffee

However! FrontStreet Coffee wants to emphasize that Golden Cup Extraction is merely a concept - a standard established based on the preferences of a specific group of people. We must recognize that different countries have different dietary habits, and we cannot ensure that everyone will prefer the same standard. Therefore, Golden Cup Extraction should only serve as a reference. We can use it to better understand coffee extraction, but we should not apply this theory to all coffee. Coffee within the Golden Cup range is not necessarily delicious, and coffee outside this range is not necessarily unpleasant. As long as the brewed coffee tastes good to you, it's your "Golden Cup Coffee," even if it doesn't fall within the Golden Cup range!

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