Standard Extraction Time and Ratios for Espresso: Why Can't Espresso Be Extracted Twice?

Principles of Espresso Extraction

For more premium coffee knowledge, please follow the official WeChat account: FrontStreet Coffee

Every coffee shop's essential pre-opening task is to calibrate a qualified and delicious espresso. While we understand what makes espresso taste good, what exactly constitutes a qualified espresso? Today, FrontStreet Coffee will discuss the extraction of espresso coffee.

Espresso coffee (in Italian, Espresso) is essentially a percolation method using precision metal filters. Compared to gravity percolation (pour-over), the biggest difference is pressure.

An espresso machine forces high-pressure water through the coffee puck, meaning that even when the coffee grounds themselves are extremely fine, it can still ensure moderate percolation and balanced extraction. The finer the coffee grounds, the larger their surface area grows exponentially, so one major advantage of ultra-fine grounds is particularly fast extraction speed. Not only is it fast, but the quality is also superior. High pressure can force water into the internal cell walls of the coffee grounds, achieving effects like extracting emulsified oils and dissolved sugars that gravity alone cannot accomplish.

Espresso represents coffee with complex yet concentrated flavors—no other brewing method can present such richness and texture. To obtain a delicious cup of coffee, excellent extraction is essential, achieving a balance between aromatic compounds and taste compounds in the cup. Simply put, the acidity, sweetness, and bitterness should all be pleasant, therefore requiring tasting to judge the state of the espresso.

Why Can't Espresso Be Extracted Twice?

Coffee extraction is a complex physical process. By bringing coffee grounds into contact with water, soluble components from the coffee transfer into the water, creating coffee liquid. Roasted coffee beans consist of soluble aromatic substances (about 30%) and woody fiber (about 70%). The Golden Cup Standard suggests that when coffee extraction rate falls within the 18-22% range, the extracted coffee substances are relatively delicious.

Soluble aromatic substances attach to the cell walls of roasted beans and are dissolved upon contact with water, then carried out with the water—this is what we call coffee extraction. The darker coffee beans are roasted, the looser their internal structure becomes, and the substances within are more easily broken down and released. As water continuously washes over the coffee grounds, aromatic substances are released. After about 22% of aromatic substances have been extracted, if water injection continues or a second brewing occurs, what continues to be released are large molecular substances with undesirable flavors.

Factors Affecting Espresso Extraction

Similar to pour-over coffee, espresso extraction parameters play a crucial role in the flavor of the coffee, but they are not fixed numbers. For example, when brewing tea, both extending the steeping time and reducing the water amount can result in a more concentrated tea. The same applies to coffee extraction liquid—as long as you understand the relationships between parameters, extracting a delicious espresso is not difficult. Below, FrontStreet Coffee will use our store's espresso production as an example to discuss several key factors in extraction. FrontStreet Coffee uses our own roasted "Sunflower Warm Sunshine Blend," composed of Honduras Sherry and Ethiopian Yirgacheffe Natural Red Cherry.

1. Dose-to-Yield Ratio

The extraction ratio includes the dose of coffee grounds and the weight of extracted coffee liquid. The amount of dose largely depends on the size of the portafilter basket. FrontStreet Coffee's store coffee machine comes with 20-gram capacity double portafilter baskets, and we use 20 grams of coffee grounds for production, then adjust up or down based on the espresso extraction status of the day.

As FrontStreet Coffee mentioned above, the more water poured through coffee, the lower the concentration of the coffee liquid, the flatter the taste, and the less concentrated the flavors. Therefore, an appropriate dose-to-water ratio is very important. The dose-to-yield ratio generally falls between 1:1.5 and 1:2.5, with 1:2 being commonly used, such as extracting 40g of coffee liquid from 20g of coffee grounds.

2. Grind Size

In most cases, extracting an espresso takes only a few dozen seconds. Within such a short extraction time, to extract the complete aroma from coffee, the coffee grounds need to be ground finer and more evenly, which requires a dedicated electric grinder designed for espresso extraction.

The grind size needs to be adjusted to an appropriate range. If the particles are too coarse, extraction is likely insufficient, resulting in weak coffee flavor and prominent acidity. If the grind particles are too fine, the coffee is easily over-extracted, resulting in bitter taste. Additionally, because the fineness of espresso grinding is much higher than that of pour-over methods, adjustments cannot be too drastic, as this can lead to excessive variables and more unstable extraction.

3. Extraction Time

Flavor compounds in coffee begin reacting the moment they contact water. Extraction time refers to the period from when we press the extraction button until the water flow stops, typically controlled between 25-30 seconds. When we keep the dose-to-yield ratio fixed at 1:2, we control the time by adjusting the grind size and dose. If the time is less than 25 seconds, the espresso may tend to be thin, weak, with obvious acidity. If the time exceeds 30 seconds, it may tend toward scorching bitterness and irritating flavors. FrontStreet Coffee's extraction time during production is usually 29-30 seconds, stabilizing flavor compounds while avoiding over-extraction of large molecular substances.

4. Flow Rate

Flow rate is the speed at which coffee liquid flows down. The ultimate goal of our extraction parameters is actually a flow rate result.

Typically, normal espresso should begin dripping the first drop of coffee liquid around the fifth second after pressing the extraction button, with subsequent flow being relatively uniform. The speed of the flow directly reflects whether the grind size and ratio are appropriate. If the first drop of coffee liquid doesn't appear until after more than 10 seconds (excluding pre-infusion), the grounds might be too fine or the puck might be tamped too densely. If the flow rate is too fast or spraying occurs, the grounds are too coarse, or channeling is happening.

5. Pressure and Water Temperature

When we've just extracted a fresh espresso, you can notice a layer of crema floating on top, composed of numerous small bubbles. This is called crema, and it's a distinctive feature of espresso made from fresh coffee beans.

Coffee beans produce large amounts of gas during roasting. Under high pressure, water dissolves carbon dioxide from them, but as the brewed coffee gradually returns to normal atmospheric pressure, the coffee liquid cannot continue to trap all gas components, so countless small bubbles emerge from the liquid. These bubbles remain on the surface of the coffee liquid, looking like a stable layer of "foam." As gases within coffee beans continuously release over time, the further from the roasting date, the lower the carbon dioxide content, and the thinner the crema layer during extraction. Therefore, fresh roasted coffee beans and sufficient pressure are indispensable factors for forming crema.

Typically, semi-automatic espresso machines have extraction pressure around 9-10 bar, and water temperature generally between 90-94 degrees Celsius. The higher the water temperature, the more substances are released in the same amount of time. Excessively high temperatures can easily lead to scorching bitterness in coffee, while too low temperatures result in insufficient extraction and flat flavors.

Espresso Bean Recommendations

Delicious dishes depend on good ingredients, and a delicious espresso naturally requires flavorful, high-quality coffee beans. FrontStreet Coffee's bean menu offers four types of espresso beans, all espresso blends created through multiple comparisons and formulations by FrontStreet Coffee.

Classic Full-Bodied Type – FrontStreet Coffee Commercial Blend Beans

Robusta Washed Coffee Beans (10%) + Colombian Washed Coffee Beans (30%) + Brazil Natural Pulped Coffee (60%)

The extracted espresso features rich golden crema and nutty aroma. When tasting, you'll experience scorching coffee bitterness, but more prominently, a creamy full-bodied texture. After swallowing, the bitterness dissipates, leaving a fragrant aftertaste.

Slightly Acidic Full-Bodied Type – FrontStreet Coffee Basic Blend Beans

Yunnan Washed Arabica Coffee Beans (30%) + Brazil Natural Pulped Coffee Beans (70%)

Yunnan arabica coffee with gentle acidity pairs with the full-bodied aroma of Brazilian Cerrado coffee. The espresso presents flavors of caramel, nuts, and soft plum acidity.

Balanced Rich Aroma Type – FrontStreet Coffee Premium Blend Beans

Colombian Washed Coffee Beans (30%) + Brazil Natural Pulped Coffee Beans (70%)

Adding Colombian coffee to the classic nutty notes of Brazilian coffee results in espresso with dark chocolate flavors, caramel sweetness, and full roasting aroma.

Delicate Wine Aroma Type – Sunflower Warm Sunshine Blend Beans

Ethiopian Natural Red Cherry Coffee Beans (30%) + Honduras Sherry Barrel Coffee Beans (70%)

Made into espresso, it presents very rich dark chocolate flavor with strong caramel notes. The aroma released after swallowing is endlessly memorable. Whether diluted with water for Americano coffee or enhanced with milk for latte coffee, both present rich aroma and flavor.

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

For more premium coffee beans, please add the private WeChat FrontStreet Coffee, WeChat ID: qjcoffeex

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473