Let’s take a closer look at one of the most important brewing methods in coffee: espresso. Even if your go-to drink is a pour-over or a cappuccino, espresso is almost certainly your starting point. Learning about how espresso works helps you understand the mechanics of the brewing process as a whole, including extraction and flavor balance.
What Is Espresso?
Espresso isn’t a type of coffee, like Arabica or Robusta. It’s a brewing method. It’s all about pushing hot water through coffee grounds in a special way. Espresso differs from filter coffee because it’s brewed using pressure, producing a smaller volume of liquid but with a much higher intensity of coffee flavor and a layer of crema on top.
How Grind Size Affects Espresso
The grind size is critical when preparing espresso because it affects the speed at which the water passes through the coffee grounds and, consequently, the extraction process. With the short time it takes to brew espresso, typically around 25 to 30 seconds, the grind must be very fine and consistent. If the grind is too coarse, the water will flow through too fast, resulting in weak, under-extracted coffee with a sour taste. On the other hand, a grind that is too fine will cause the water to flow slowly or not at all, leading to an over-extracted coffee with a harsh, bitter flavor. Consistency is also key; even small changes in the grind size can make a significant difference in the taste of the coffee.
Dose and Yield
The dose is the amount of coffee you put in the portafilter, while the yield is the amount of liquid coffee you end up with. These are usually measured in grams because the same volume of coffee can weigh differently depending on how fine the grind size is. A good starting point for most people is to use 18 grams of coffee and pull about 36 grams of espresso from it. But it all comes back to balance, so this isn’t set in stone.
Time
Time also plays an important role in the extraction process, so keep an eye on your espresso machine to make sure you aren’t rushing the brewing process. Most people aim to extract their espresso over 25 to 30 seconds or so, but this is more of a starting point than a hard rule. If it brews too fast (say, in under 20 seconds), you’re going to get an under-extracted shot with a lot of sourness and very little body. If it brews too slowly (over 35 seconds), your shot is going to over-extract with a very bitter, harsh flavor.
Pressure and Machines
To get the coffee puck to the right temperature to brew espresso, you need to force water through it with pressure. For a while, the industry standard was around 9 bars. While it’s good to know the right pressure setting is important for getting your espresso, your machine isn’t the end-all be-all. A great brewer with a good home espresso machine can produce just as good of espresso as a professional barista with an expensive, precision espresso machine. What’s important is to understand these different factors and how they affect the quality of your extraction and flavor.
Tamping
Before brewing your shot, you have to tamp, or press the espresso grounds into the basket. If the coffee grounds aren’t pressed tightly, the water will not go through them evenly. This leads to channeling, which can cause an under-extracted shot with a bitter taste. It’s essential to tamp your grounds firmly and evenly to ensure a uniform brew. If you have a good tamper and a good espresso machine and you tamp them correctly, you’re going to have a very smooth espresso with great flavors.
Tasting
You need to taste your espresso. This is important because you’re going to notice things as the balance changes depending on how you brew your espresso. You want it to have a balance, so it’s not too sour but also not too bitter. It shouldn’t be overwhelmingly dark in the cup, with an intense sweetness in the middle and a lingering flavor at the end. Once you can taste all these things, you know how well you’ve extracted your coffee, and you can start to understand how origin and roasting also affect your cup.
Conclusion
Espresso may be the easiest method to understand, but it is also one of the most precise because the flavor comes from a lot of little factors, such as the grind size, dose, time, and pressure. The more you learn how this works, the more you’ll understand how everything in coffee works, which will help you make great-tasting coffee every day.