What is Espresso? How Do Espresso Machines Make Espresso?

Understanding Espresso Coffee: A Complete Guide

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What is Espresso Coffee?

Since Starbucks entered China, you can see "Italian coffee" mentioned everywhere on streets and alleys. What exactly is Italian coffee? What does Espresso mean? Let me explain this to everyone so you can have a better understanding of Espresso!

The Meaning of Italian Coffee

Actually, in previous articles, the meaning of Italian coffee was already mentioned - it refers to coffee beverages based on Espresso, including latte, cappuccino, macchiato, and con panna, among others. (Strictly speaking, latte should be considered Seattle-style coffee, as "latte" in Italy only means pure milk.) So to understand Italian coffee, we must first understand what Espresso really is.

The Nature of Espresso

In the Italian mindset, Espresso is a dark-colored beverage served in a thick, small cup, topped with reddish-brown foam (crema), containing less than 50cc of liquid. (Domestic coffee enthusiasts like to describe it as "reddish-brown," which is close to the color of almond bean skins.) Every day, nearly 50 million cups of Espresso are consumed worldwide, with its aroma and taste serving as an important morning stimulant.

The Meaning Behind "Espresso"

Espresso contains the meaning of "express," indicating speed (not referring to delivery services) - it's a beverage that must be made to order and consumed immediately. There's a saying: "the consumer, not the Espresso, must wait," which means the consumer needs to wait, while Espresso should be drunk immediately after preparation and cannot be left waiting for someone to drink it. This is because once Espresso is prepared, it has a layer of "crema" that must be consumed before this foam dissipates, otherwise it will lose its smooth texture. Additionally, as it gradually cools down over time, increasing acidity and unbalanced salty flavors will emerge. Of course, some enthusiasts prefer to wait until Espresso cools down to drink it, wanting to experience its cold texture, because the tongue has different taste sensitivities at different temperatures.

The Importance of Pressure

Another aspect of Espresso that is very different from other brewing methods and extremely important is pressure. In the early 20th century, to quickly provide customers with coffee in a short time, the method of increasing brewing water pressure was developed. This involved putting water in a sealed heating pot and boiling it, where the pressure generated by water vapor could accelerate coffee extraction efficiency (the same principle as today's moka pot). However, this method had a drawback - it couldn't extract coffee at the correct temperature (around 90°C water), causing boiling water to scorch the coffee grounds and produce a more bitter taste. Later, another method was developed to generate pressure - using the barista's arm strength to create pressure, which produced Espresso with crema (later springs were added to provide more stable pressure than human arms). Today, most coffee machines use electric pumps to provide labor-saving and stable pressure for coffee extraction.

Extraction Time

Another important characteristic of Espresso is extraction time. Espresso extracted using pressure can efficiently bring both water-soluble and fat-soluble substances into the cup. The optimal average time is about 30 seconds. Less than 15 seconds results in under-extraction, producing weak-tasting coffee with unbalanced acidity, while more than 30 seconds results in over-extraction, producing harsh, unpleasant-tasting coffee.

Definition of Espresso

Therefore, Espresso has a quantitative definition: Espresso is a small amount of coffee extracted from ground roasted coffee beans with hot water under specific time conditions. (Italian espresso is a small cup of concentrated brew prepared on request by extraction of ground roasted coffee beans, with hot water under for a defined short time.)

Related Parameters

Some relevant parameter ranges are as follows:

Ground coffee dose: 6.5 ± 1.5g

Water temperature: 90 ± 5°C

Injection water pressure: 9 ± 2 bar

Extraction time: 30 ± 5 sec.

Coffee volume: 15~50 ml, optimal 25~30ml (according to consumer or barista's personal preference)

The above is the definition of Espresso. In the future, if you order a cup of Espresso at a coffee shop and see only about 30cc of coffee, don't slam the table and accuse the owner of cheating you.

References

Some content in this article is translated from the book "Espresso Coffee, The Science of Quality."

Technical Definition

Definition of Espresso:

Espresso is a brew obtained by percolation of hot water under pressure through tamped/compacted roasted ground coffee, where the energy of the water pressure is spent within the cake.

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