How does an espresso machine turn coffee into a shot?

A good Americano, latte, or cappuccino starts with a qualified espresso shot. Espresso machines use a precision metal filter screen and internal high pressure to push water through the coffee puck, so even very fine grounds still percolate at a steady speed. Four variables control the result: dose, time, yield, and grind size.

High pressure pushes water into the cell walls of coffee particles, releasing oils and aromatic compounds. Beans are roughly thirty percent water-soluble, but only about twenty percent are pleasant aromatic small molecules that extract first; woody, bitter large molecules need longer. Adjusting parameters shifts more of the good components into the cup.

To make a good Americano, latte, or cappuccino, the first step always comes down to a qualified espresso. From Front Street's perspective, this article first explains the pressure extraction principle of espresso machines, then breaks down the four adjustable variables of dose, time, yield, and grind size, goes on to explain why blended beans are better suited for espresso output, and provides a complete workflow from distribution and tamping to extraction observation, finally offering judgment approaches for daily parameter adjustments to help you steadily control the flavor in the cup.

In daily life, we don't really order a straight espresso to drink on its own, but to make common drinks like Americano, latte, and cappuccino, a qualified espresso base is an unavoidable prerequisite. This time Front Street will discuss how to pull a good shot of espresso.

How is an espresso machine different from other brewing methods?

Espresso relies on a precision metal filter screen to complete percolation extraction. Compared with the drip method of pour-over, the most critical difference lies in pressure. The machine's internal high pressure pushes water through the coffee puck. In other words, even if the coffee is ground extremely fine, it can still maintain a proper percolation speed and balanced extraction result. The finer the coffee grounds, the more their surface area expands exponentially, so one major advantage of very fine grounds is that extraction is especially fast. Not only fast, but the quality is also more ideal. High pressure can also push water into the cell walls inside the coffee particles, releasing rich oils and aromatic flavor compounds.

No matter which method is used to brew coffee, the essential goal is to use water to bring out the positive flavors in the coffee and obtain a delicious cup of coffee liquid. Coffee beans have a complex composition, with about thirty percent of substances soluble in water, such as fruit acids, caffeine, oils, carbohydrates, and so on. Among them, only about twenty percent are pleasant-tasting aromatic small molecules that are released first; the remaining large molecules with woody and bitter notes need longer to be extracted. So what a barista needs to do is adjust the corresponding parameters so that more of the high-quality components in the coffee enter the cup.

Espresso represents a type of coffee with complex flavor and high concentration, and other brewing methods find it difficult to present the same body and texture. To taste good, excellent extraction is indispensable, and the aromatic compounds and taste compounds in the cup must reach a balance. Simply put, the acidity, sweetness, and bitterness should all be comfortable to drink, so tasting is used to judge the state of the espresso and then decide how to adjust it to produce a qualified espresso.

From an operational standpoint, from a coffee bean to a cup of espresso, quite a few variables are involved, including grind size, boiler pressure, water temperature, distribution and tamping force, dose, extraction time, extraction yield, and so on. Usually the machine pressure and temperature are preset and not changed at will. Distribution and tamping are controlled according to the barista's habits. The four major factors actually used in daily extraction adjustment are dose, time, yield, and grind size. As the saying goes, a clever housewife cannot cook a meal without rice; for good cooking, the ingredients must be up to standard, so the quality of the coffee beans is very important.

What coffee beans should be used for espresso?

Espresso is extracted under conditions of fine grinding, high water temperature, and high pressure. The espresso gathers multiple tastes, and various flavor compounds impact the taste buds exponentially. Therefore, if a light-roasted single-origin bean is used to make espresso, the taste may be too aggressive and instead cover up the coffee's aroma. Coffee is, after all, an agricultural product. When climate and soil change, even from the same origin, the flavor of each batch of beans will differ, while blended beans make up for each other's shortcomings, allowing each batch to show balanced and stable aroma and mouthfeel.

For espresso, Front Street's classic espresso blend is recommended. This recipe is composed of beans from three origins: Brazil, Indonesia, and Vietnam. It uses a dark roast, which highlights the coffee's mellow aroma to the greatest extent and also makes it easy for everyone to extract rich, dense crema. Whether adding water to make an Americano or pairing it with milk to make a latte, it is very suitable. It can be purchased and ordered at the Front Street Taobao store or the Front Street Tmall flagship store.

Freshly made espresso has a thick, dense golden foam on the surface, which is crema. This is formed by the carbon dioxide produced by freshly roasted beans foaming under the machine's high pressure. In order for the coffee's full aroma and complete enjoyable period to be tasted, Front Street only ships fresh coffee beans within 5 days after roasting.

Steps for making espresso

The espresso coffee served daily at Front Street stores uses the "Sunflower Warm Sun Blend." The baristas at Front Street Coffee (FrontStreet Coffee) debug the espresso extraction parameters before opening the store every day, and only then do they formally begin serving.

Front Street uses the capacity of a double basket, with a dose roughly between 18 and 20 grams, and takes 20 grams of coffee powder when serving. The extraction ratio is 1:2, that is, 20 grams of powder extracts 40 grams of coffee liquid. Time is related to the flow rate of the coffee, and a single extraction is generally controlled at 20 to 35 seconds, because within 20 seconds the taste tends to be thin, while over 35 seconds it is easy to over-extract and produce a burnt bitterness. Front Street's espresso mostly falls in the 28 to 30 second range.

Before extraction, wipe the basket dry, open the grinder and grind a double dose, place it on the electronic scale and adjust until it is exactly 20 grams. Then use a distribution tool to level the coffee surface, and then use a tamper to press vertically downward, compacting the puck firmly so that extraction is more stable.

Then turn on the extraction switch and let water run for 1 to 2 seconds to moisten the group head and rinse off any coffee grounds stuck to it. Place an electronic scale under the cup receiving the Espresso and tare it to zero, then place it together under the group head during extraction.

Gently lock the portafilter onto the group head and flip down the extraction switch. Pay attention to the changes in the extracted liquid. When the electronic scale shows that 40 grams of coffee liquid has been extracted and the time is about 30 seconds, pull the switch down to stop. Brewing parameters will change slightly with daily air humidity and bean condition, so the dose, grind setting, and extraction yield all need to be adjusted up or down accordingly.

The extracted Espresso can be drunk directly. Paired with a cup of water to rinse the mouth, you can taste the dense oily foam and the mellow mouthfeel of the coffee liquid underneath. If you cannot accept the strong bitterness, you can also add water or milk according to your preference to dilute and soften the intense taste.

Suggestions for adjusting parameters when making espresso

In daily brewing, extraction adjustment relies heavily on experience, especially when making coffee at home and producing only a few cups, where small fluctuations in various factors can easily affect the final taste. Front Street suggests that everyone record various parameters more often to make it easier to summarize and adjust. For example, Front Street stores debug before opening every day, and if all parameters are within the preset range, then there is no need to make large changes. Instead, directly taste the flavor of the espresso to judge the extraction state, and then make minor adjustments to the above parameters.

If, under the same extraction ratio, the espresso shows negative flavors such as burnt bitterness but the concentration is moderate, then the time may be too long and the burnt bitterness has been extracted. The usual solution is to adjust the grind size coarser. Conversely, when the espresso tastes weak and the concentration is low, it may be that the flow rate is too fast or the dose is too small, causing under-extraction. You can increase the dose or adjust the grind finer to raise the extraction concentration. These parameters will continuously change in conjunction with the extraction state. Only by paying more attention to the adjustment direction brought by extraction variables can you better control the high-quality flavor of the coffee in the cup.

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