To make a balanced espresso at home, the key is to master a few core variables that affect extraction. Based on Front Street Coffee's practical experience, this article systematically sorts out the relationships among the four adjustable parameters—dose, grind size, brew ratio, and extraction time—to help readers understand how to determine the direction of adjustment based on the taste the espresso presents. The article also introduces the basic concept of the Golden Cup standard, explains why choosing more stable espresso blend beans can improve the fault tolerance of home extraction, and lists four espresso blends with different styles from Front Street's bean list for reference.

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Some people fall in love with espresso starting from a rich-aroma americano; some are drawn in by delicate latte art patterns; others are fond of milk coffee with a velvety texture. The foundation of these drinks all comes down to a well-extracted espresso. Many friends hope to make the same taste at home, so they ask Front Street for troubleshooting methods. In this article, Front Street will discuss how to adjust espresso extraction parameters.

What counts as the best extraction?

No matter which brewing method is used, the essence is to use water to bring out the positive flavor substances in coffee and finally obtain a delicious coffee liquid. About 30% of the components in coffee beans can dissolve in water, such as fruit acids, caffeine, oils, and carbohydrates. Of these, only about 20% are aromatic small molecules with positive flavor performance, which are dissolved first; the remaining large molecules with woody and bitter notes need more time to enter the water.

To get a delicious cup of coffee, we should retain as many positive flavors as possible and produce as few negative tastes as possible. There are several industry-recognized standards for this trade-off ratio, which is what we often call the Golden Cup standard. Of course, when ordinary people make espresso at home, they rarely use professional equipment such as a refractometer, but if they want to make coffee with just the right concentration and extraction yield, they still need to grasp a few key factors that affect extraction.

What parameters should you understand for making espresso?

From a coffee bean to a cup of coffee liquid, there are many variables that affect flavor, including grind size, coffee machine boiler pressure, water temperature, distribution and tamping force, dose, extraction duration, yielded liquid weight, and so on. Generally speaking, the pressure and temperature of the coffee machine will not be changed frequently once set; distribution and tamping force vary according to the barista's personal habits. In daily operation, the four most commonly used to adjust extraction are dose, time, liquid weight, and grind size.

Grind size

The coarseness of the grind and the uniformity of the particles are the most critical factors causing differences in the flow rate of each espresso. Even if the dose differs by only 1 gram, the time required to extract the same liquid weight may differ by several seconds. When the coffee powder particle sizes are inconsistent, the denser areas after tamping create greater resistance to water flow, making extraction uneven. Grind size directly affects the flow rate of the coffee liquid, extraction time, and the final flavor direction.

Brew ratio

The ratio between the dose and the extracted liquid weight is what is commonly called the brew ratio, and it is a relatively intuitive extraction parameter. The dose depends on the specification of the portafilter basket, which can be single or double. For example, the coffee machine at Front Street's store uses a double dose of 20 grams of coffee powder and makes fine adjustments on this basis, accurate to 0.1 grams. Since the brew ratio is not fixed, the yield ultimately still depends on the coffee's flavor performance.

In the past, baristas did not have the habit of precise weighing, but instead directly observed changes in the color of the crema to judge when to stop the shot: when it first flowed out, it was dark brown and thick in texture, then gradually turned golden yellow, and then light yellow. Usually when the crema began to turn white, it meant the extraction should end. Today, espresso extraction standards are more rigorous and the data is more stable, and the brew ratio has gradually trended toward a fixed reference value—1:2. For example, Front Street's store uses 20 grams of coffee powder to extract 40 grams of coffee liquid.

Extraction time

Extraction time is affected by factors such as grind size, dose, and whether the coffee powder is evenly distributed, and it also in turn affects flow rate and brew ratio. The extraction time of espresso is usually controlled between 25 and 30 seconds. Under the premise of a fixed brew ratio, the shorter the time, the faster the flow rate, and the fewer coffee substances are dissolved; the longer the time, the slower the flow rate, and the more substances are dissolved. Under the same brew ratio, if you want to change the extraction time, you can only do so by adjusting the grind size or dose.

In daily extraction, to control concentration and extraction yield within the ideal range, the variables we can adjust are usually grind size and brew ratio, combined with the actual taste the espresso presents for judgment. For example, under the same extraction ratio, if the espresso shows negative flavors such as burnt bitterness, but the concentration is still moderate, this may be because the time is too long and burnt bitter flavors have been extracted. The usual solution is to make the grind coarser. Conversely, if the espresso tastes weak and the concentration is low, it may be under-extracted, which can be solved by increasing the dose or making the grind finer.

The above parameters influence one another as the extraction state changes. We need to pay more attention to the direction of adjustment brought by extraction variables in order to more accurately capture the excellent flavors in the cup.

Espresso coffee bean recommendations

Most home espresso machines are not as stable in performance as commercial machines and produce fewer cups, which places greater demands on our ability to control parameters. Therefore, Front Street recommends choosing espresso blend coffee beans with higher stability. Espresso blends combine the coffee flavors of different producing regions and use medium-dark roasting, allowing us to have a higher fault tolerance during extraction. There are four espresso blends available on Front Street's bean list, and only coffee roasted within 5 days is shipped, ensuring that everyone receives it while it is still in the best tasting period.

Classic rich type—Front Street Commercial Blend Coffee Beans

Washed Robusta coffee beans (10%) + washed Colombian coffee beans (30%) + semi-washed Brazilian coffee (60%)

The espresso made has rich golden crema and nutty aroma. On the palate there is a toasty coffee bitterness, but it is accompanied more by a creamy full body. After swallowing, the bitterness fades, leaving aroma between the lips and teeth.

Slightly acidic rich type—the espresso coffee beans recommended by many baristas—Front Street Black Cocoa Blend Coffee Beans

Washed Yunnan Arabica coffee beans (30%) + semi-washed Brazilian coffee beans (70%)

The soft acidity of Yunnan Arabica, combined with the rich aroma of Brazilian Cerrado coffee, gives the espresso a taste of caramel, nuts, and soft plum acidity.

Balanced rich-aroma type—Front Street Specialty Blend Coffee Beans

Washed Colombian coffee beans (30%) + semi-washed Brazilian coffee beans (70%)

Adding Colombian coffee to the nutty tone of classic Brazilian coffee, the espresso shows dark chocolate flavor, caramel sweetness, and a full roasted aroma.

Delicate wine-aroma type—Sunflower Warm Sun Blend Coffee Beans

Espresso made from Ethiopian sun-dried Red Cherry coffee beans (30%) + Honduran Sherry Barrel coffee beans (70%). On the palate it is a rich dark chocolate flavor with an obvious caramel note, and the aroma released after swallowing is memorable. Whether it is an americano diluted with water or a latte with milk added, it presents rich aroma and mouthfeel.

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