How does an espresso machine work with grind size and brew ratio?
Espresso grind should be fine enough to slow the shot into a balanced range, and the brew ratio is the main lever for adjusting it. Regular espresso usually falls between 1:1.5 and 1:2.5, and Front Street shops use 1:2, meaning the liquid yield weighs twice the dose of dry coffee.
Dose and yield are the two numbers the ratio covers: a single basket holds about 8–9 g and a double about 18–20 g, producing roughly 28–30 g of liquid in the conventional range. Grind size, water temperature and extraction time interact with that ratio, so changing one usually calls for a small adjustment to the others.
Espresso has always been known for being rich and intense, but to consistently produce a delicious cup of Espresso, the parameters that need to be controlled are far more complex than one might imagine. The interplay between grind size, dose, yield, time, and water temperature—each of these can change the final flavor direction. This article starts from the brew ratio, combines the hands-on experience of Front Street Coffee shops, and sorts out the logic for judging espresso grind size and the approach to adjusting extraction parameters, helping coffee enthusiasts find a balance between flow rate and flavor and quickly dial in a balanced cup of espresso.
\n\nFor more specialty coffee knowledge, please follow our WeChat official account: Front Street Coffee (FrontStreet Coffee)\n\nItaly can be called the birthplace of coffee culture. Espresso spread from there to the world, and it can be regarded as the soul role in the coffee family, as well as a precious gift Italy has given to the world. As its name suggests, Espresso is quick to make and quick to drink, with an intense, concentrated flavor—a small cup condenses the essence of coffee.\n\nHowever, making espresso is far from as easy as drinking it, and there are quite a few parameters that need to be calibrated. Grind size, water temperature, extraction time, brew ratio, and so on—each one directly affects the quality of the espresso. Among them, the extraction ratio especially requires precision. This time Front Street will focus on the espresso extraction ratio and talk about the ins and outs behind it.\n\n
\n\nThe brew ratio\n\nThere is no universally fixed value for the extraction ratio; in practice it needs to be adjusted flexibly according to the situation. However, there are indeed some conventional reference values in the industry, usually forming general standards based on influential practices and becoming benchmarks within the industry. For regular Espresso, the extraction ratio mostly falls within the range of 1:1.5 to 1:2.5, and Front Street shops use 1:2.\n\n
\n\nThe extraction ratio involves two aspects: the dose and the weight of the resulting coffee liquid. In China, the extraction ratios for single and double shots usually correspond to the capacity of the portafilter basket on the coffee machine: a single shot is about 8–9 grams, and a double shot is about 18–20 grams, extracting 28–30 grams for a single shot and 30–40 grams for a double shot of espresso liquid within 25–30 seconds. The coffee machine used by Front Street shops is equipped with a 20-gram-capacity double basket. When producing, 20 grams of coffee are dosed, 40 grams of coffee liquid are extracted, and slight upward or downward adjustments are made according to the day's espresso extraction condition.\n\nIncreasing or decreasing the dose changes the compactness of the coffee puck, which in turn affects the flow rate of the espresso. The more coffee there is, the denser the puck, and the slower the flow rate of the coffee liquid. The time required to extract the same beverage weight is then lengthened, the coffee liquid becomes stronger, and the extraction yield is higher. Generally speaking, the flow rate and flavor performance should be combined to judge how the dose should be slightly increased or decreased.\n\n
\n\nGrind size\n\nIn most cases, a cup of espresso can complete extraction in just a few dozen seconds. To fully release the coffee aroma in such a short time, the coffee grounds must be ground finer and more evenly, so an electric grinder specifically for espresso extraction is needed.\n\nEspresso extraction magnifies coffee flavors exponentially, so the requirements for grind size are especially strict. Grind size is difficult to distinguish with the naked eye and is usually reflected in the flow rate and flavor of the espresso. When the grind is coarser, the coffee particles are larger, the puck is looser, and the time for water to pass through the coffee bed is shortened, which easily causes underextraction, with a bland, sour flavor. When the grind is finer, overextraction is more likely, resulting in a bitter taste and a sharp mouthfeel. In addition, espresso grinding is far finer than methods such as pour-over, and adjustments should not be too large, otherwise the variables become too great and extraction becomes more unstable.\n\n
\n\nHow to adjust extraction parameters\n\nEspresso extraction changes with air humidity brought by the weather and with the condition of the coffee beans. For example, rainy days are more humid than sunny days, and coffee grounds easily absorb more moisture, thereby affecting subsequent extraction. When extracting espresso, water temperature and pressure are rarely changed easily and are usually set at fixed parameters. For example, the coffee machine at Front Street shops uses 9 bar of pressure and a water temperature of 94°C. Daily dialing generally revolves around the three parameters of grind size, dose, and coffee liquid weight to adjust the flavor in the cup.\n\nFor example, the extraction parameters Front Street used the day before were: 19.8 grams of coffee grounds, 38 grams of coffee liquid, and a time of 29 seconds. If the same dose is used to extract and 38 grams of espresso are obtained, but the time is shortened to 26 seconds, it indicates that the flow rate has become faster.\n\n
\n\nAt this point, Front Street will first try increasing the dose by 0.1 gram each time to change the flow rate. When using 20 grams of coffee grounds, extracting the same beverage weight, and bringing the time back to 29 seconds, tasting the espresso shows no strange bitterness, but the aroma is slightly flat, indicating underextraction. This also means that the effect of simply adding coffee is not obvious enough, and it is necessary to switch to adjusting the grind size—at this time it should be made finer, so that the particles are smaller and the flavor substances are fully released. Conversely, if the flow rate becomes slower, first speed it up by reducing the dose. If reducing the dose still does not work, then adjust the grind coarser.\n\nThe direction of parameter adjustment is flexible. As long as you are familiar with the characteristics of the coffee beans and the coffee machine, it is not difficult to quickly dial in a delicious espresso. After adjustment, Front Street produces a normal cup of espresso here, and everyone can refer to it. Front Street uses its own roasted "Front Street Sunflower Warm Sun Blend Coffee Beans," made from a blend of 30% Yirgacheffe natural Red Cherry and 70% Honduras Sherry.\n\n
\n\nFront Street will use 20 grams of coffee grounds, follow a 1:2 brew ratio, and extract 40 grams of coffee liquid under 9 bar of pressure, with the time controlled at 30 seconds.\n\n
\n\nThe flavor performance of this cup of espresso is a rich whisky aroma, accompanied by the acidity and fragrance of berries; as the temperature drops slightly, vanilla and cream flavors gradually emerge, and the finish is dark chocolate. Overall it is balanced, with a rich and smooth mouthfeel.
The above content is compiled by CoffeeHunters, a coffee news website.
