Learn How Espresso Works: Crema, Extraction, Pressure, and Hot Water

I love walking into a coffee shop and hearing the sound of a barista steaming milk to make a cappuccino. However, you won't be able to truly appreciate that delicious specialty drink without a few shots of espresso (and maybe a caramel drizzle).

What is espresso?

This rich, bold drink was invented in Italy in the early 20th Century by inventor Luigi Bezzera. The word “espresso” literally means pressed or squeezed and refers to the process of extracting a shot of this drink by pushing hot water through fine ground coffee with high pressure.

To make espresso, you need an espresso machine that is capable of turning raw coffee beans into steaming cups full of flavor quickly and easily. There are methods to make espresso-style beverages without using pressure, but they lack many of the characteristics of a genuine espresso shot.

Espresso has a stronger flavor and makes about 30ml (one ounce) per shot, whereas auto drip coffee makers create huge pots of coffee.

Water

There is nothing more important than water when it comes to making coffee. Because water makes up 98% of the drink, you need to make sure it tastes great and is free from impurities like chlorine or other chemicals.

When you get ready to select your espresso machine, pay attention to what water source you have. Some espresso machines use a water tank that can be filled up with filtered water, while others require you to hook it directly into your water line.

For brewers using a plumbed system (direct water line), it is vital to make sure the machine has an internal filter installed in case there are any impurities or issues with your tap. This is important because if your water is not clean, it can affect the taste of your coffee and cause buildup inside the espresso machine.

Check with local water companies to see if there are any known issues in your area that may affect the quality of your tap water, and consider investing in a home filtration system for coffee or just better tasting water.

Coffee Grounds

Water and grounds are the yin and yang of coffee brewing. The water is the starting point and can create astringent flavors if not adequately filtered, while the grounds can make your espresso taste sour if they're not fresh.

When brewing with an espresso machine, it is crucial to use finely ground beans that resemble a very fine powder or flour consistency. If you grind them too coarsely (like granular sugar), your drink will be sour.

You probably noticed that most espresso roasts are dark (or even extra dark), but that's not a required roast level. You can use lighter roast coffee and still pull a great shot. You can expect more floral and fruity notes with a brighter, more acidic flavor with a lighter roast espresso.

There is no right or wrong when it comes to the roast level, and espresso drinkers have distinct preferences. If you're just starting out, we would recommend trying several roast levels until you find the one that satisfies your taste buds!

Temperature

The ideal temperature for espresso is around 195°-205°F degrees Fahrenheit (91°-96°Celcius). Because each roast is unique, you will need to dial in the temperature to get the perfect extraction.

Higher temperatures result in bolder, sweeter flavors requiring faster extraction. Lower temperatures produce more complex flavors that are less sweet but highlight brighter flavor notes.

If you've ever drunk a bad brew, then you know the importance of the temperature. Over extracted coffee tastes bitter and hollow, while under extracted coffee tastes sour and lacks any depth.

Some less expensive espresso machines don't have temperature controls. In this case, you can adjust your grind size to improve extraction levels. For instance, if your coffee is too sour, you can grind a step finer for a faster extraction that brings out more sweet flavor in each cup.

Coffee Brewing Temperature 3

The Puck

Unlike other methods of brewing coffee, espresso requires compressing the ground coffee. This is where the coffee puck enters the picture (no, we're not talking about ice hockey). The puck is created by tamping the grounds tightly into the portafilter.

Water is lazy. It seeks out the path of least resistance through coffee grounds. If you have an unevenly compressed puck, your water will create channels and flow through them in only a few areas, resulting in an unevenly extracted brew.

It's important to note that more compression on the puck does not seem to improve extraction.


Extraction

Everything leading up to now has been important, but the extraction is where it all comes together.

Espresso machines use hot water and steam pressure to extract flavor from the fresh ground coffee beans. Pressure is created by a pump or the espresso machine's boiler before water flows through a portafilter basket nozzle on top.

The standard pressure of an espresso machine is 9 bars (about 130 PSI). The bar is the average atmospheric pressure at sea level. Why 9 bars? The packed puck and small holes in a portafilter provide a significant barrier to water flow.

We talked about temperature earlier, but it's important to note that pressure affects extraction as well. High-pressure machines will create more complex flavors with lower acidity. Low-pressure machines result in a bolder, more acidic cup.

The water is heated to your desired temperature, then sent through the coffee puck at high pressure to extract all of the flavor components from the grounds. The extraction process takes about 25 seconds to completely flow into your espresso cup or demitasse. If you pull shots for longer than 30-45 seconds they will be over extracted, resulting in a bitter tasting espresso.

If you're using an inexpensive machine, your extraction may be uneven due to the inconsistency of water pressure throughout the brewing process. If this is happening to you, try tamping with more or less force until it extracts evenly.

Crema

Created through the unique espresso process. Crema is the golden, tan foam on top of an espresso shot. It's produced by emulsifying the oils that are extracted from the grounds with water, which gives each cup its signature taste.

Crema also acts as a signpost to help you figure out how your extraction process is going. Crema should be thick but dissipate quickly after pouring. If it doesn't disappear within a minute or so, the coffee was likely under-extracted.

The consistency of the crema is also a barometer for how well you've tamped down the coffee grounds in the portafilter basket. A poorly compressed puck means that there isn't even pressure on all the coffee grounds to extract the full flavor. A good puck should result in a thick crema that quickly dissipates after pouring your shot into an espresso cup or demitasse.

Do you Need an Espresso Machine?

Making espresso requires an espresso machine that is able to create pressure. There are a number of home espresso machines capable of brewing that perfect espresso shot.

Most modern espresso machines are capable of brewing a great cup with very little input. There are also manual espresso machines that use leverage to create pressure. These are great if you don't have a lot of countertop space and are willing to put in a little more muscle work.

There are even stovetop espresso machines capable of creating the proper amount of pressure needed. These home espresso machines even come with a steam wand!

Final Thoughts

Knowing how espresso works helped me appreciate the art of coffee brewing. The science behind the process is fascinating and it's cool to know how it all comes together.

The most important thing is knowing how your espresso machine works and making sure you're using the proper grind size, tamping down the grounds evenly, and keeping an eye on extraction time. Once you have this knowledge under your belt, creating a delicious cup of coffee will be easy!

This is a guest post written by Kris Silvey from ElevatedCoffeeBrew.com
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