At Front Street Coffee, before opening the doors every day, we always dial in the espresso extraction parameters first before attending to anything else. This is because all the other espresso-based drinks served at Front Street locations require espresso as their base, so you can imagine just how important a delicious shot of espresso is.

Espresso is made using a fully automatic or semi-automatic espresso machine, where under the right conditions (high temperature, high pressure), hot water is forced through finely ground coffee at tremendous pressure, rapidly extracting a liquid with rich crema, intense aroma, and a heavy mouthfeel.

Some friends who have enjoyed a full-bodied, aromatic espresso at a café hope to recreate it at home, so they ask Front Street how to adjust espresso parameters and ratios at home. Setting up an espresso extraction recipe is all about making our coffee taste better. Although home equipment often doesn't perform as well as commercial machines, as long as we find the right coffee-to-liquid ratio, extraction time, and grind size, we can pull a delicious shot of espresso.

Before we talk about extraction, Front Street suggests first choosing a bag of fresh blend coffee beans with a medium roast level and full aroma. We know that coffee's flavor comes from factors like origin, variety, processing method, and roast level. Roasters understand the unique character of each coffee bean, blending beans from two or more origins and dialing in the corresponding roast profile, so that our espresso has a more stable flavor, a more balanced taste, and a higher tolerance for extraction error.

Every time Front Street serves an espresso-based drink, you can see a thick, velvety layer of crema floating on top, giving off an intense wine-like aroma—this is the mark of freshly roasted coffee beans. After coffee is ground into powder and extracted under high pressure, the carbon dioxide in the coffee grounds becomes wrapped in the coffee oils, forming dense little bubbles. Blended coffee beans need 4 to 10 days of degassing and resting after roasting before entering a stable flavor peak stage. Darker-roasted blends typically need 10 days of degassing. The coffee beans Front Street ships are all freshly roasted within 5 days. When you receive them, they may still be in a relatively fresh resting period, so Front Street suggests waiting a few days before extracting.

Back to extraction—a delicious cup of coffee should have a moderate amount of soluble aromatic compounds brought out into the liquid. The Golden Cup standard holds that when the extraction yield is between 18-22%, the extracted coffee compounds are at their most delicious. Therefore, we need to control the coffee-to-liquid ratio, time, and grind size to adjust how much is extracted.

The extraction ratio is the ratio of coffee dose to liquid yield. There's actually no completely fixed parameter for the extraction ratio—it needs to be adjusted according to different situations. Espresso extraction ratios are generally controlled between 1:1.5 and 1:2.5, and Front Street locations use a 1:2 ratio. The espresso machines at Front Street locations are paired with 20-gram double baskets. When serving, we use 20 grams of coffee to extract 40g of espresso liquid, then adjust up or down based on that day's espresso extraction condition.

Increasing or decreasing the dose changes how compact the coffee puck is, which in turn determines how fast or slow the espresso flows. The more compact the puck, the slower the flow of coffee liquid, and the longer it takes to extract the same amount of liquid—resulting in a more concentrated shot with a higher extraction yield. Generally speaking, you need to judge based on flow rate and flavor to decide how to make tiny adjustments up or down.

Typically during extraction, with all other parameters unchanged, the shorter the extraction time, the fewer coffee compounds are dissolved; the longer the extraction time, the more coffee compounds are dissolved. When we fix the coffee-to-liquid ratio at 1:2, adjusting grind size and dose to keep extraction time between 25-30 seconds is the fastest way to dial in espresso.

Because espresso extraction amplifies coffee flavors, the requirements for grind size are very strict, and adjustments are quite small. It's hard to judge grind size coarseness with the naked eye—it usually shows up in the flow rate and flavor of the espresso. If the grind is too coarse, the coffee particles are larger, the puck is looser, and water passes through the coffee faster, leading to under-extraction with a thin, sour flavor. If the grind is too fine, the coffee is easily over-extracted, tasting bitter with a sharp mouthfeel.

Friends who have visited Front Street locations for espresso drinks probably know that Front Street has always used its own roasted "Front Street Sunflower Warm Sun Blend Coffee Beans," made from 30% Front Street Yirgacheffe Natural Red Cherry and 70% Front Street Honduras Sherry.

Front Street uses 20 grams of coffee powder, follows a 1:2 coffee-to-liquid ratio, and extracts 40 grams of espresso under 9 bar of pressure, with the time controlled at 30 seconds.

The espresso has a flavor of intense whisky-like aroma, with the tartness of berries. As the temperature drops slightly, vanilla and cream flavors begin to emerge, with a dark chocolate finish. The overall balance is even, and the mouthfeel is rich and smooth.

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The above content is compiled by CoffeeHunters, a coffee news website.