Want Stronger Coffee? Why Not Just Extract Longer?

In daily operations, FrontStreet Coffee often encounters customers who prefer a stronger coffee flavor, typically requesting an extra shot. However, one customer, when asking for a more concentrated coffee, said, "Can you help me extract the coffee for a longer time?"

According to this customer's understanding, the longer the extraction time, the more coffee liquid obtained, resulting in higher coffee concentration in the cup. Is this really true? Let's not rush, let's start with a small experiment.

FrontStreet Coffee, based on that day's standard parameters, kept the grind setting and coffee dosage constant while extracting at three different time points to collect the corresponding espresso weights. We then tested the coffee concentration of each group and tasted their flavors. (Experimental premise: espresso is measured by weight in grams, not by volume.)

Coffee beans: FrontStreet Coffee · Sunflower Warm Sunshine Espresso Blend

Grind setting: Galileo Q18 setting 2.0

Dosage: 20 grams

Extraction time: 30 seconds, 35 seconds, 40 seconds

Group 1: 30 seconds extraction yielding 35g of coffee liquid, with a TDS value of 12.11%

Flavor profile primarily features berry acidity and fermented wine notes, accompanied by cocoa's mellow bitterness, with a finish of vanilla and nutty roasted aromas.

Group 2: 35 seconds extraction yielding 46g of coffee liquid, with a TDS value of 8.83%

Flavor mainly consists of caramel, cocoa, and slight wine notes, with unremarkable acidity and an almond-like bitter aftertaste.

Group 3: 40 seconds extraction yielding 55g of coffee liquid, with a TDS value of 7.80%

The lowest mouth viscosity among all groups, with an unappealing flavor profile dominated by barley tea and woody notes, almost no acidity, and a slight irritating sensation after swallowing.

Next, let's carefully observe a complete extraction process, examining how the espresso state changes, while using three separate cups to collect the early, middle, and late segments of the coffee extraction.

From the first drop of espresso, the liquid is as thick as hot chocolate, dark brown in color, and most concentrated in flavor, with a sharp acidity when tasted. The color then gradually lightens to golden yellow, and the flow rate increases, with lower concentration than the first cup, resulting in a more balanced taste. When the electronic scale shows over 35 grams, the liquid has turned completely yellow, while the crema begins to turn white and solidify. The late-stage espresso tastes mildly bitter and slightly sweet, with the weakest aroma.

Similar to the coffee-to-water ratio often mentioned in pour-over brewing, a delicious coffee requires proper extraction—neither under-extracted nor over-extracted. However, because the water output volume of espresso machines is difficult to measure directly, the industry more commonly uses the coffee-to-liquid ratio as a reference to judge and measure espresso extraction concentration.

The coffee-to-liquid ratio is influenced by two factors: coffee dosage and coffee liquid weight. The generally recommended extraction ratio ranges from 1:1.5 to 1:2.5, with 1:2 being the most common. For instance, FrontStreet Coffee's original standard parameters use 20g of coffee grounds to extract 40g of coffee liquid, while the experimental groups 2 and 3 had ratios of 1:2.3 and 1:2.75 respectively, significantly higher than the original value.

Theoretically, a delicious cup of coffee should have a moderate amount of soluble aromatic substances extracted by hot water. The Golden Cup Standard suggests that coffee extraction yields are most flavorful within the 18-22% range. When the crema begins to turn yellow until it becomes white, it's actually telling us that all the flavorful substances in the coffee have been released and it's time to stop extraction. If hot water continues to flow through the coffee bed at this point, only undesirable bitter macromolecular substances remain, which enter the cup with the liquid.

Combining this with the previous experimental data, we can conclude that when the grind setting and dosage remain constant, and the liquid weight exceeds the original coffee-to-liquid ratio's maximum threshold (for good taste), as extraction time increases, the greater espresso yield means more hot water has passed through the coffee grounds, extracting more soluble substances, thus resulting in a higher extraction rate. At the same time, more water also means the coffee is more diluted, so the concentration becomes lower, and there are fewer positive coffee flavors.

For this reason, if you want to obtain a rich, flavorful, and more robust espresso base, asking the barista to extract more coffee liquid is clearly not reliable. If you don't want to add more shots of espresso, you might ask if they can replace the Espresso with a Ristretto—that's right, just like the Ristretto mentioned by FrontStreet Coffee yesterday.

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FrontStreet Coffee

10 Bao'an Front Street, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

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