How Are Coffee Brewing Yield and Strength Actually Calculated?
The Gold Cup figures of 1.15%-1.35% concentration and 18%-22% extraction yield come from the SCAA, not the SCA. The two associations merged in 2017, and the UC Davis Coffee Research Center later adjusted the old brewing control chart, raising the upper concentration limit and widening the coffee-to-water ratio range. A reading like 1.37% is therefore not automatically a fault.
Coffee extraction and strength interact: high concentration with low extraction tends to highlight acidity, while low concentration with high extraction can bring out floral and chocolate notes. Judging a cup means reading both numbers together rather than fixating on one. The old and new control charts differ mainly in how much room they allow at the edges of the recommended range.
Many coffee enthusiasts have heard of the Golden Cup extraction theory: ideal concentration 1.15%-1.35%, ideal extraction yield 18%-22%. But this standard actually comes from the SCAA, not the SCA. The European and American coffee associations each have their own views on ideal concentration. After the SCAA and SCAE merged in 2017, the UC Davis Coffee Research Center made minor adjustments to the old brewing control chart, relaxing the upper concentration limit and the coffee-to-water ratio range. This article will start from the history of the Golden Cup theory, sort out the differences between the old and new control charts, explain why high concentration with low extraction can highlight acidity while low concentration with high extraction can reveal floral and chocolate notes, and combine product information from Front Street Coffee to help you understand how to comprehensively judge concentration and extraction yield, rather than fixating on just one number.
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Previously, a barista shared a personal experience: a customer ordered a cup of Yirgacheffe pourover. Just as the barista finished extraction, the customer did not rush to drink it, but instead took a spoonful of the coffee liquid and measured it with a TDS concentration meter. The result showed that the concentration reached 1.37%, and the customer immediately pointed out that this had already exceeded the 1.15%-1.35% range stipulated by the SCA Golden Cup standard. The barista suggested that the customer take a sip first and said it could be remade if unsatisfied, but the customer insisted that the shop was not professional enough and directly cancelled the order and left.
When it comes to the optimal values of Golden Cup extraction, many people immediately think of the idea that a cup of coffee's ideal concentration should fall within 1.15%-1.35%, and the ideal extraction yield should be between 18%-22%. But it needs to be clarified that this concentration range is not the SCA standard, but was proposed by the SCAA (Specialty Coffee Association of America). Although the ideal extraction yield of the Golden Cup theory is universally set at 18%-22%, when it comes to ideal concentration, the various coffee associations in Europe and the United States each have their own views. The ideal concentration given by the SCAA is 1.15%-1.35%, the SCAE (Specialty Coffee Association of Europe) advocates 1.2%-1.45%, and the NCA (National Coffee Association) considers 1.3%-1.55% appropriate.
The origins of these concentration ranges can be traced back to the 1950s and 1960s. At that time, Dr. Lockhart used total dissolved solids (TDS) and extraction yield as quantitative bases for judging coffee quality, and worked with multiple research institutions to create a coffee brewing control chart. Over the following decades, this chart almost became a textbook-level reference in the fields of coffee extraction and Golden Cup theory.
However, factors such as coffee bean quality and roasting preferences have been constantly changing. Some content in the original Golden Cup extraction theory can no longer match today's advanced equipment, diverse extraction methods, and the way people perceive flavor. After the SCAA and SCAE merged into the SCA in 2017, the SCA joined forces with the UC Davis Coffee Research Center in the United States to revise the coffee brewing control chart and published a slightly adjusted version in 2019.
The most core difference between the old and new control charts is that even if coffee falls outside the Golden Cup ideal values, it is not necessarily undrinkable. After the minor adjustment, the upper limit of ideal concentration was raised, expanding from 1.35% to 1.45%; the recommended brewing coffee-to-water ratio was also broadened from 1:15-1:20 to 1:14-1:20; and the tolerable upper concentration limit was raised from 1.6% to 1.8%. At the same time, the definition of "bitterness" was also changed to over-extraction.
The revised chart helps distinguish sensory descriptions from consumer preferences. To put it plainly, the old chart's explanation of concentration was too arbitrary. For example, when a cup of coffee tastes rather bitter (regardless for now of whether the drinker can accept this bitterness), as long as the concentration exceeds the ideal range, the old chart would directly classify it as bad bitterness.
Another situation is like the case at the beginning: can our senses really distinguish the difference between 1.35% and 1.37%? But limited by the fixed settings of the chart, even if no difference can be perceived in taste, it would still be directly judged as unsatisfactory concentration and undrinkable coffee, thereby ignoring the real sensory experience and making the evaluation of coffee unfair.
Although the chart has been slightly adjusted, some issues remain unresolved. For example, when discussing whether coffee tastes good, people often only look at concentration and do not talk about extraction yield—once the coffee is not smooth, the first reaction is that it is too strong; or conversely, they only talk about extraction yield and not concentration, and immediately say it is over-extracted.
Subsequent research by the SCA found that the presentation of certain flavors in coffee requires deviating from the ideal range in order to perform well. Today, coffee flavors are becoming increasingly rich. If brewing follows the ideal extraction yield and concentration 100%, the final flavor obtained may not be the best state.
According to joint analysis by the Coffee Research Center and the SCA, coffee beans of different roast levels need extraction yields and concentrations below or above the ideal range for their distinctive flavors to be fully displayed. Acidity, citrus, and dried fruit flavors usually appear in situations of high concentration and low extraction. The intensity of acidity and citrus generally increases as concentration rises, but weakens as extraction yield increases. Moderate high concentration with low extraction can enhance the pleasant acidity in coffee; but if high concentration with low extraction goes too far, it will bring a sharp, uncomfortable sourness. Tea-like notes, floral notes, and chocolate flavors often appear in situations of low concentration and high extraction, while sweetness is mostly seen in states of low concentration and low extraction.
However, whether in the original version or the slightly adjusted version, the logic of the chart is always: high concentration means strong, low concentration means weak. But some pleasant flavors perform best precisely at low concentration, yet the chart uniformly labels such cases as "weak." For this reason, Teacher Han Huaizong pointed out in The Fourth Wave of Specialty Coffee that these two charts may be misleading.
The Golden Cup extraction guideline is ultimately just a reference scale set by specialty coffee, with the purpose of reducing disputes caused by differences in how different people judge coffee concentration. It does not mean that coffee will definitely taste good if it falls 100% within the standard values, or that it will definitely taste bad if TDS is slightly high or low.
The meaning of drinking coffee should inherently be to make yourself happy, pleased, and comfortable. What matters is that you like drinking it. Even if the concentration displayed by the TDS meter is not within the ideal range of the Golden Cup theory, as long as you think it tastes good, then it tastes good. Drinking coffee does not have to be like attending a chemistry class; it does not require you to cautiously pursue every precise number.
Image source: Internet
The above content is compiled by CoffeeHunters, a coffee news website.
