Coffee Extraction Science | Espresso Coffee Bean Extraction Standard Brew Ratio SCA Golden Cup Extraction Theory

What is Golden Cup Extraction?

In FrontStreet Coffee's articles, we often reference the concept of "Golden Cup Extraction." Some friends have left messages in our comments section asking what exactly "Golden Cup Extraction" means.

Understanding Golden Cup Extraction

Golden Cup Extraction refers to using a cup of coffee's concentration and extraction rate as reference points to determine whether the coffee has been properly extracted. The current Golden Cup standards specify an extraction rate between 18%-22% and a concentration between 1.15%-1.35%.

Origins and Development

This concept originated in the United States in 1952, when the American Coffee Association collaborated with Dr. Lockhart, a chemistry PhD from MIT, to research and promote standards for the coffee industry. For this purpose, they established a Brewing Committee. Dr. Lockhart and his team studied the structure and chemical composition of coffee beans, ultimately discovering that coffee beans contain 30% soluble substances and 70% insoluble fiber materials.

Following this discovery, they immediately took action by conducting coffee preference surveys among random American consumers. This research concluded that the preferred extraction rate ranged from 17.5%-21.2%, with concentration between 1.04%-1.39%, thereby establishing the initial Golden Cup Extraction range. However, since pour-over coffee wasn't popular in America at that time, the tests used relatively coarse grind sizes and quite high water temperatures to brew coffee, with extraction times reaching 4-8 minutes. As you can see, there were significant instability factors in both the people and the coffee involved.

Modern Golden Cup Standards

Subsequently, professional organizations conducted multiple rigorous analyses and expert tastings, ultimately correcting the Golden Cup numerical range. The extraction rate was adjusted to 18%-22%, while concentration remained between 1.15%-1.35%. This revised Golden Cup Extraction was recognized by the Specialty Coffee Association of America (SCAA) and has been used ever since. Some friends might ask: What exactly is concentration? And what is extraction rate?

Understanding the Golden Cup Extraction Chart

We can observe the Golden Cup Extraction Chart below to better absorb and understand the Golden Cup extraction theory:

The horizontal axis represents extraction rate, while the vertical axis represents concentration. Concentration refers to the amount of extractives contained in our cup of coffee - more extractives mean stronger coffee, fewer mean weaker coffee. Extraction rate refers to the proportion of soluble substances obtained from the coffee powder relative to the total coffee grounds used. We can obtain concentration values using a coffee concentration refractometer, then calculate the extraction rate using the formula: "coffee volume × coffee concentration ÷ coffee grounds weight."

Understanding the Grid Lines

Incidentally, the Golden Cup Extraction Chart contains diagonal grid lines that represent the coffee-to-water ratio - the proportion of coffee grounds to corresponding hot water used for a cup of coffee. The upper left corner of the chart contains English annotations that essentially tell us that each diagonal line uses 1.9 liters of water, corresponding to the coffee grounds amount opposite that line.

So we can make a quick calculation: 1900ml ÷ 135g = 14.07, which gives us the first diagonal line's coffee-to-water ratio of 1:14.07. By extension, we continue until the third diagonal line, which just crosses into the dark area of the chart.

The Ideal Extraction Zone

This dark area represents the ideal extraction zone for a cup of coffee - what we call the Golden Cup Extraction range: extraction rate between 18%-22% and concentration between 1.2%-1.45%. Coffee that exceeds this range is considered over-extracted, while coffee that doesn't reach this zone is under-extracted.

A Common Misconception

However, this chart can easily lead to a misunderstanding: that as long as you choose a diagonal coffee-to-water ratio that falls within the Golden Cup Extraction range, you can definitely brew delicious "Golden Cup Coffee."

This is not the case. The coffee-to-water ratios that reach the Golden Cup Extraction zone in the chart don't necessarily guarantee that your brewed coffee will taste good - they are merely reference data points. What they express is that these coffee-to-water ratios make it easier to brew within the Golden Cup extraction range.

The True Purpose of Golden Cup Theory

We study Golden Cup Extraction theory because it helps us better understand extraction, identify improper brewing factors, and thereby brew the flavors we desire. Therefore, we must not misunderstand the Golden Cup extraction philosophy or limit ourselves to golden ratio coffee-to-water proportions.

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