How does an espresso maker work and what ratios apply?

An espresso machine forces hot water near 92 degrees Celsius under high pressure through a finely ground, tamped puck of coffee. The liquid that comes out is the base of Italian-style drinks such as the americano, latte, cappuccino, and flat white. Key controls are the powder-to-liquid ratio, extraction time, and TDS, which together give the extraction percentage.

The workflow runs from wiping the portafilter basket through tamping, pulling the shot, and cleaning the group head. Measuring TDS lets you check whether the shot is under- or over-extracted, and adjust grind or dose accordingly. The article also lists recipe ideas and flavor notes for four Front Street espresso blends, plus the shop's own extraction scheme.

Espresso is the foundation of various Italian-style drinks such as Americano, latte, and cappuccino. It is extracted by forcing hot water at about 92 degrees Celsius under high pressure through a finely ground and tamped layer of coffee powder using an espresso machine. This article focuses on the extraction standards of espresso, covering the powder-to-liquid ratio, extraction time, TDS measurement, and calculation of extraction percentage, and outlines the complete operational steps from wiping the portafilter basket to cleaning the group head. It also introduces the recipe ideas and flavor characteristics of four espresso blend beans from Front Street Coffee, as well as the espresso extraction scheme of Front Street stores, providing a systematic reference for coffee enthusiasts.

Although most people who come to Front Street for pour-over coffee are in the majority, there are also quite a few customers willing to order espresso drinks. Everyone knows that espresso forms the base of various Italian-style drinks—Americano, latte, cappuccino, flat white, mocha, without exception.

Front Street has learned that espresso is called "espresso" abroad, and its caffeine content per unit volume also exceeds that of most coffee drinks. It is extracted by an espresso machine, with the principle of forcing hot water (usually at about 92 degrees Celsius) under high pressure through a finely ground and tamped layer of coffee powder. During this process, solids and soluble components are extracted, and the resulting liquid is espresso. Espresso is both the origin of all coffee drinks and a standalone coffee beverage in itself. Many people habitually regard it as the representative of Italian-style coffee and compare it with Americano. So what exactly is the difference between Italian-style coffee and Americano?

There are two ways to make Americano. One is extracted by a drip coffee maker, and the other is made by adding water to espresso. To understand the difference between these two methods, we can start with the history of Americano. Drip coffee makers were first popularized in American households, and Americans were accustomed to the coffee made by drip machines—lighter in taste, thin in body, and noticeably watery. During World War II, the coffee that American officers drank in Europe was almost all espresso, strong and stimulating.

To recreate the flavor of drip coffee, they added water to the espresso liquid, which made the coffee taste much softer and much smoother to drink. At that time, people in other European countries did not drink coffee this way, so this beverage was given the name "Americano." This term actually carried a sarcastic tone, a joke by locals about Americans not being used to espresso. The French even privately called Americano "sock coffee" to describe how poor its taste was.

The Americano at FrontStreet Coffee is made by adding water to espresso, and most coffee shops on the market also use this method. Generally speaking, the water-to-liquid ratio of Americano ranges from 1:4 to 1:9, with different coffee shops having different standards. Front Street's hot Americano has a water-to-coffee-liquid ratio of 1:4.5, which was determined by combining the characteristics of the Sunshine Blend espresso and the store's serving cup size. Front Street's iced Americano has a water-to-coffee-liquid ratio close to 1:9. Because it uses the store's own blended espresso beans, FrontStreet Coffee's Americano does not deliberately pursue nutty notes, but instead presents a rich wine aroma, with abundant crema, a full body, a creamy mouthfeel, and a long chocolate finish. Compared with hot Americano, iced Americano is more refreshing. With different espresso beans, the flavor of the coffee drinks made will also change accordingly. Front Street has designed four espresso beans for different needs: Specialty Blend, Commercial Blend, the espresso moka pot coffee beans recommended by many baristas—Front Street Dark Cocoa Blend, and Sunshine Blend.

The espresso moka pot coffee beans recommended by many baristas—Front Street Dark Cocoa Blend—uses beans from Brazil, Colombia, Yunnan, and other origins commonly used for espresso, aiming to achieve better flavor and mouthfeel at a lower cost. For coffee shops seeking rich crema, Front Street's Commercial Blend adds 10% robusta beans, which enhances the overall body while also making the coffee flavor richer and mellower. The nutty flavor is prominent, and the chocolate flavor paired with the sweetness of milk is very harmonious. The Specialty Blend uses arabica coffee beans from Brazil and Colombia. All-American arabica can present a cleaner coffee taste, and the flavor expression of these two producing regions is nutty and chocolatey, making them very suitable for espresso production.

Sunflower Sunshine Blend coffee beans were a new experiment by Front Street in 2019. At that time, the concept of specialty (single-origin) coffee was prevailing, and many SOEs sold on the basis of flavor had also appeared, but Front Street planned to use high-quality single-origin beans for blending to make a blended coffee bean whose main purpose was flavor. In the end, Front Street settled on using 30% Yirgacheffe Red Cherry and 70% Honduras Sherry as the recipe for Sunflower Sunshine Blend coffee beans. The rich vanilla cream and fermented wine aroma attracted a large audience.

Generally speaking, espresso extraction has certain standards. Depending on the portafilter basket, the weight of coffee powder is usually between 18-22 grams. Make sure the weight of the coffee powder matches your target, because a tiny difference can lead to a huge difference. The most common brewing ratio is twice the coffee powder, meaning if you have 18 grams of coffee powder, it is best to extract 36 grams of espresso liquid. Once this value is exceeded, the coffee is prone to over-extracted flavors.

Of course, this standard can also be adjusted according to individual needs. For example, the espresso served at Front Street stores uses 20 grams of powder to extract 36 grams of coffee liquid, in order to make the resulting Americano and latte more aromatic and fuller in flavor. Here we should remind everyone that the weight of the liquid coffee is best 1-3 times that of the dry coffee powder, with 2 times being commonly used.

The brewing time starts from pressing the button and ends when extraction is complete, usually falling between 25-35 seconds. If the extraction time is longer or shorter than expected, the main reason is the coffee grind size. You can adjust it according to your own needs to optimize the extraction parameters.

Generally speaking, a faster extraction speed will make the coffee's acidity more prominent and reduce its sweetness. A slower extraction speed will give the coffee a bitter and dull flavor.

The most direct way to judge whether espresso is ready to serve is to taste it. Taste is a good method for judging the quality of espresso. However, because judging whether espresso is normal by taste alone is too subjective, some far-sighted baristas and roasters use refractometers to measure the total dissolved solids (TDS) in espresso. TDS measurement allows them to determine accurate brewing strength and extraction percentage, and to relate their preferred brewing parameters to numerical data. Measuring TDS also means we can calculate the extraction percentage using the following formula:

(%TDS x brewed coffee weight) / coffee powder weight = extraction percentage

Many coffee enthusiasts who come to Front Street show admiration for the baristas operating the coffee machine at the bar, curious about how they operate such an apparently complex coffee machine. In fact, what baristas master is merely the detailed steps of making espresso; as for how the coffee machine operates, most baristas do not understand it. So today, Front Street will introduce the detailed production process of espresso. Taking the normal operating process of FrontStreet Coffee as an example:

Step 1: Wipe the portafilter basket to ensure the coffee powder basket is dry and free of water

Step 2: Weigh the coffee powder, using an electronic scale to weigh an appropriate amount of coffee powder, keeping the error within plus or minus 0.1 grams

Step 3: Distribute the powder

Step 4: Tamp the powder

Step 5: Lock in the portafilter

Step 6: Press the button to extract

Step 7: Remove the portafilter, clean the group head.

Front Street espresso extraction scheme recommendation: 20g powder, extract 40g coffee liquid, time 30 seconds

And just like that, one espresso is finished extracting. If you want to make other coffee drinks, it is simply a matter of adding sugar or milk. Iced coffee is relatively simpler to make, as it is just adding hot espresso to cold milk. As for hot milk coffee, you will need to use the steam wand on the coffee machine. Regarding how to steam milk foam, FrontStreet Coffee has also written a dedicated article for teaching. If needed, everyone can look it up themselves. It is worth mentioning that many coffee chain brands now use fully automatic coffee machines, making operation even simpler—just press a button.

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style)

For more specialty coffee beans, please add the private WeChat of FrontStreet Coffee, WeChat ID: kaixinguoguo0925

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