How Do Coffee Particles Behave During Espresso Extraction?

Espresso is the base for Americano, latte and cappuccino. A precision metal filter and pump pressure push water through the puck, so even fine grounds percolate evenly. Because grinding finer multiplies surface area, extraction runs fast and pressure forces oils and aromatics out of the coffee particles, which is why grind size, dose, time and yield must be tuned together rather than changed one at a time.

Roughly 30 percent of a coffee bean dissolves in water, but only about 20 percent of that carries the positive aromatic compounds, and those come out first. Woody and bitter large molecules need longer contact. The barista's job is to set parameters so more of the good material lands in the cup and the result is a delicious coffee shot.

Espresso is the foundation for making popular coffee drinks such as Americano, latte, and cappuccino. This article will systematically explain the extraction principles of Espresso, equipment characteristics, coffee bean selection, and practical operating steps, helping coffee enthusiasts master the key points for extracting a good shot of espresso. The article covers adjustment approaches for core parameters such as grind size, dose, extraction time, and yield, while also introducing the standard daily workflow at Front Street stores and the recommended "Sunflower Warm Sun Blend Coffee Beans," providing practical reference for home brewing and daily production.

We rarely go out of our way to drink a straight espresso, but to make common drinks like Americano, latte, and cappuccino, a qualified Espresso as the base is essential. This time Front Street will talk with everyone about how to extract espresso better.

What makes an espresso machine different when making espresso?

Espresso relies on a precision metal filter screen for percolation extraction, and the biggest difference from pour-over drip brewing lies in pressurization. The high pressure inside the machine pushes water through the coffee puck, and even if the coffee grounds are ground very fine, it can still maintain proper percolation and balanced extraction. The finer the grind, the more the surface area increases exponentially, so a notable advantage of very fine grounds is that extraction speed is very fast, and the quality is better as well. High pressure can force water into the internal structure of the coffee particles, prompting rich oils and aromatic substances to be released.

No matter which method is used to brew coffee, the goal is to use water to bring out the positive flavors in the coffee and obtain a delicious coffee liquid. Coffee beans are composed of many components, of which about 30% are soluble in water, including fruit acids, caffeine, oils, carbohydrates, and more. Of these, only about 20% are positive-flavor aromatic small molecules, which are extracted first; the remaining large molecules with woody and bitter notes take longer to dissolve out. Therefore, what a barista needs to do is adjust the relevant parameters so that more of the high-quality components in the coffee are extracted.

Espresso represents coffee with complex flavor and high concentration, and other brewing methods find it difficult to present such richness and texture. To get a delicious cup of coffee, excellent extraction is indispensable, and the aromatic compounds and taste compounds in the cup need to reach balance. Simply put, the acidity, sweetness, and bitterness should all feel pleasant, so tasting is used to judge the state of the espresso, and then decide how to adjust to make a qualified shot of espresso.

From an operational perspective, there are many factors affecting the transformation of a coffee bean into a cup of espresso, including grind size, boiler pressure, water temperature, distribution and tamping force, dose, extraction time, extraction yield, and other details. Usually the machine's pressure and water temperature are set in advance and are not changed at will. Distribution and tamping force vary according to the barista's habits. In daily extraction adjustment, four major factors are mainly used: dose, time, yield, and grind size. As the saying goes, "One cannot make bricks without straw." For food to be delicious, the ingredients must be well chosen, and the quality of coffee beans is equally crucial.

What kind of coffee beans should be chosen for espresso?

Because espresso is extracted under conditions of fine grinding, high water temperature, and high pressure, espresso brings together multiple tastes, and various flavor compounds impact the taste buds exponentially. If a light-roasted single-origin bean is chosen for extraction, the taste may be too intense and instead mask the coffee's aroma. Coffee is an agricultural product and changes with factors such as climate and soil. Even if produced in the same region, the flavor of each batch of beans will differ. Blended coffee beans use the method of compensating for weaknesses with strengths, ensuring that each production shows balanced and stable aroma and mouthfeel.

Front Street here recommends its own roasted "Sunflower Warm Sun Blend Coffee Beans," blended from Ethiopian natural Red Cherry coffee beans (30%) and Honduras Sherry Barrel coffee beans (70%). After being made into espresso, it enters with flavors of sherry, vanilla, and cream, plus the tropical fruit and fermented notes of Red Cherry, making the whole cup rich yet gentle. The aroma released after swallowing is memorable for a long time. Whether it is an Americano diluted with water or a latte with milk added, it can present rich aroma and mouthfeel.

A freshly made espresso will be covered on the surface with a thick, dense golden foam, which is crema. It is made of bubbles formed under high pressure from carbon dioxide produced by freshly roasted coffee beans. In order for everyone to drink full coffee aroma and enjoy the most complete tasting window, Front Street only ships fresh coffee beans within 5 days after roasting.

Steps for making espresso

The espresso drinks produced daily at Front Street stores all use the "Sunflower Warm Sun Blend." The baristas at Front Street Coffee (FrontStreet Coffee) debug the espresso extraction parameters before opening every day, and only then begin formal production.

Front Street uses the capacity of a double basket, with a dose of about 18–20 grams, and uses 20 grams of coffee grounds during production. The extraction ratio is 1:2, meaning 20 grams of coffee grounds extract 40 grams of coffee liquid. Time is related to the flow rate of the coffee grounds. Generally, a single extraction is controlled within 20–35 seconds, because within 20 seconds the coffee taste tends to be thin, while over 35 seconds it is prone to over-extraction and burnt bitterness. Most of Front Street's espresso falls within the 28–30 second range.

Before extraction, wipe the basket dry, turn on the grinder to grind the amount for a double shot, and place it on an electronic scale to increase or decrease until it reaches 20 grams. Then use a distribution tool to level the coffee grounds, and then use a tamper to press straight down with force to compact the coffee puck, ensuring more stable extraction.

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

Gently lock the portafilter onto the group head and flip down the extraction switch. Observe 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, flip down the extraction switch. Brewing parameters will change slightly due to daily air humidity and the condition of the coffee beans, so it is necessary to adjust the dose, grind setting, and extraction yield up or down.

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 rich 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 mouthfeel.

Suggestions for adjusting parameters when making espresso

In daily brewing, extraction adjustment needs to be discussed in combination with experience, especially when making it at home, where the number of cups produced is small, and slight changes in various factors can easily affect the final taste of the espresso. Front Street suggests that everyone record various parameters more often to make it easier to summarize and adjust. For example, Front Street stores debug every day before opening. If all parameters are within the preset range, there is no need for major adjustment; instead, judge the extraction state directly by tasting the flavor of the espresso, and then fine-tune the above parameters.

If, under the same extraction ratio, the espresso shows negative flavors such as burnt bitterness but the concentration is moderate, it may be that the time is too long, causing burnt bitterness to be extracted. The usual solution is to make the grind size coarser. When the espresso tastes bland 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 concentration by increasing the dose or making the grind finer. The above parameters will continue to change correspondingly with the extraction state. We need to pay more attention to the direction of adjustment brought by extraction variables in order to better grasp the high-quality flavor of the coffee in the cup.

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 Front Street Coffee (FrontStreet Coffee), WeChat ID: qjcoffeex

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