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All About Espresso

  • By Bernie Rosenstein
Espresso is used in many coffee beverages that coffee lovers enjoy every single day. It is a key component in hot and iced espresso-based classic beverages such as lattes, cappuccinos, flat whites, and macchiatos when milk or micro foam are added to it, or a shot of espresso can simply be enjoyed by itself. You can find espresso-based beverages in any café or make them at home using an espresso machine.

Whether you’re a coffee enthusiast, a barista wanting to enhance your craft, or an aspiring coffee business owner interested in taking coffee making courses or seeking a barista training program to learn more about espresso, this guide will help you understand the components of espresso, how best to store espresso beans, the science of espresso extraction and ultimately what it takes to create consistent quality beverages using espresso.

What is espresso?

Espresso is a concentrated type of coffee made with specialty coffee beans. Espresso is made by putting finely ground espresso beans in a portafilter and having your espresso machine apply very high water pressure through the ground coffee to create a concentrated liquid.
A quality shot of espresso will have three components or layers – the crema, body, and heart
  • The crema is a golden brown creamy dense layer of foam that forms on the top layer of the espresso. It is comprised of carbon dioxide gas bubbles that attach to the coffee’s natural oils. It is an important component that influences the taste and texture of an espresso shot as it helps balance the acidic, sweetness, and bitterness of good tasting espresso.
  • The body is the middle layer below the crema and above the heart that typically has a medium caramel brown color and helps create the texture of an espresso shot.
  • The heart is the bottom layer of an espresso shot with a deep brown color and has a bitter taste that helps balance the sweetness of the crema.

A popular question that comes up all the time in our professional barista training classes – How should espresso beans be stored?

Espresso beans should be stored the same way any coffee beans should be stored – in the sealed bag that they came in or in an airtight container. The goal is to keep out air or moisture from the beans which will degrade the quality of the beans and taste of the espresso. It is not recommended to keep coffee beans in the refrigerator as this can expose the beans to unwanted moisture.

Science of Espresso Extraction

What goes into creating a quality espresso shot?

A quality espresso shot is created by understanding the espresso extraction process and knowing how to balance several variables when making espresso. The overall goal of the expresso extraction process is to balance the acidity, sweetness, and bitterness present in any quality espresso shot. To accomplish this, the following variables must be understood, controlled, and balanced:
  • Dose
  • Yield
  • Length of Extraction Time
  • Grind Size and Tamping Technique
  • Water Temperature and Pressure
And whether you are a home coffee enthusiast, barista, or an aspiring coffee business owner, the extraction process and controlling the key variables are the same whether you are creating espresso-based beverages using an expensive espresso machine in a commercial setting or a home espresso machine.

What are the general guidelines to control and balance each of the five key variables mentioned above to produce high quality espresso?

1. Dose

The dose refers to how much finely ground espresso beans you are using to create your espresso shot. Generally speaking, most cafes and commercial establishments grind 17 or 18 grams of finely ground coffee using a burr espresso grinder and place the coffee in a portafilter that attaches to the espresso machine. This is the dose required to typically make about two ounces of espresso commonly called a “double shot”. It should be noted that in a home setting, sometimes you will use less than 17 grams of finely ground espresso beans as the size of the portafilter of home-based machines will dictate how many grams it can hold.

2. Yield

The yield or output refers to the amount of espresso that will be produced in an espresso shot glass after the water goes through the ground coffee and is based on an espresso recipe. The most common recipe to achieve a standard espresso shot (i.e., typically referred to as a double shot) is a 1:2 ratio. For example, if the dose used is 18 grams, the yield will typically be about 36 grams for a classic standard double shot of espresso. Again, if your home portafilter holds fewer grams of ground coffee (e.g., 15 grams), you can still apply the 1:2 ratio to determine your target yield (e.g., 30 grams).
In contrast to the standard shot of espresso, some consumers enjoy a shorter more concentrated shot of espresso referred to as a “ristretto” shot that typically has less water and ratio of about 1:1.5 dose to yield. And some consumers enjoy espresso with more water (usually twice as much as the classic espresso shot) referred to as a “Lungo” beverage with a typical ratio of 1:4 dose to yield.

3. Length of Extraction Time

The length of extraction time refers to the speed at which water flows through the ground coffee to achieve the desired yield in the espresso shot glass. In accordance with industry guidelines, it should generally take between 23-30 seconds to achieve the desired yield and optimal taste for a classic standard double shot of high-quality espresso. The optimal taste or recipe may call for a specific time (e.g., 27 seconds) but that can vary based on a bean’s density, roast profile, and the subjective taste of the person creating the recipe. But any extraction time between 23 and 30 seconds will generally result in great tasting espresso!

4. Grind Size and Tamping Technique

As mentioned above, espresso is only made with finely ground espresso beans. However, grind size is this context refers to how fine the grind size must be to achieve the dose, yield and desired extraction time per the recipe. The burr grinders will typically produce coffee particles of equal size, but the size of each particle influences the time required for the water to pass through the ground coffee and produce the desired yield in the shot glass. 

 Additionally, once the grinder disperses the correct dose of coffee grounds into the portafilter, the loosely grounded coffee must be pushed down and compressed using a process called “tamping” to form what is commonly referred to as a puck within the portafilter. The goal is for the puck to be level, and particles evenly dispersed such that the water can saturate the particles and extract flavor. This can be achieved using a manual tool called a tamper or an automated machine such as a Pugpress.

5. Water Temperature and Pressure

The ideal temperature used in expresso extraction is generally between 195 degrees Fahrenheit and 205 degrees Fahrenheit (or 91 to 96 degrees Celsius). The water brewing pressure is commonly known as “9 bars” of pressure which is about 130 psi which is a lot of pressure. The water temperature and pressure are calibrated into the espresso machine, so they are not variables that need to be controlled by the person creating the espresso shot.
In summary, if a barista or coffee enthusiast can master the balancing of the first four variables above, they will produce high quality and great tasting espresso!

Troubleshooting Poor Tasting Espresso

What happens if your espresso is “under-extracted” or “over-extracted” resulting in poor taste and how can that be corrected to achieve great tasting espresso?

If espresso is under-extracted, it will taste too acidic, sour, salty or weak, lack sweetness and will not have enough crema. The causes of under-extraction include too little coffee used, extraction time too short, ground coffee particles used were too coarse, tamping the coffee unevenly, or water that was not hot enough.
To fix under-extracted espresso, adjust the grinder to make the ground coffee finer, or brew the coffee for a longer time, or check that the coffee grounds were properly tamped (i.e., evenly distributed).
Conversely, over-extracted espresso will taste too bitter, leave a dry mouthfeel, have dull flavors, and the crema will be a dark color and thinner than desired. The causes of over-extraction include too much coffee used, extraction time too long, ground coffee particles used were too fine, or the water temperature was too hot.
Over-extracted espresso can be fixed by adjusting the grinder to make the ground coffee coarser which will create larger particles and speed up the brew time, as well as checking that you have the correct amount of coffee brewing at the proper temperature.

Summary

Creating great tasting espresso and espresso-based beverages whether in a commercial setting or at home can be a fun and rewarding experience. Whether you are a beginner coffee enthusiast, barista, or an aspiring coffee business owner wanting to create espresso-based beverages, this guide will help you; however, it will take practice, patience, and experimentation with different espresso beans to master balancing all the variables needed to produce consistent high-quality beverages.

If you want to deepen your knowledge further and practice the art and craft of making espresso-based beverages, you may want to consider taking a barista training program or coffee making courses for home coffee enthusiasts or attending various coffee education classes at a coffee school in New Jersey where you can get hands-on experience working with coffee experts and espresso coffee equipment to hone your skills. And best of all, you will be able to enjoy making or serving customers delicious espresso-based beverages each and every day!

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