What Is Crema in Coffee?
You may have heard the word “crema” tossed around by baristas or coffee aficionados and wondered what the heck they were talking about. Crema is a hotly debated topic in the coffee world.
Some call it the holy grail of good espresso--the one true sign of a quality shot of espresso. Others disregard the hype around it as rubbish. Here we will explain everything you need to know about crema.
What Exactly Is Crema?
Put simply, crema is the thin layer of foam that sits on the top of a freshly brewed cup of espresso. Crema is a combination of tiny bubbles of CO2 released by the coffee grounds during the brewing process. It tends to be a bit more flavorful and aromatic than the actual espresso beneath--although how much it actually contributes to flavor is a subject of controversy.
How Is Crema Formed?
Crema is the result of a relatively simple chemical process. Espresso machines work by using near-boiling temperatures and pressure around 9 bars--or 130 pounds per square inch (psi). For reference, the pressure in a car tire is around 35 psi. The changes in pressure and extreme heat draw out the CO2 from within the coffee molecules.
There are essentially 3 processes that produce the layer of espresso foam. First, the extreme pressure of the espresso machine “degasses” the bean and releases CO2. Next, the sudden change in PH level in the hot water as it interacts with the grounds helps emulsify the oils on the outside of the grounds. Finally, the sudden change in pressure as the espresso exits the machine allows the CO2 to break out of the cell walls.
The primary process that affects the actual crema itself is emulsification--or the blending of the natural oils on the beans and the water. Normally, these two substances would not be able to combine. However, under the extreme pressure and heat, the oils on the coffee and water are able to temporarily mix--or “emulsify”.
Well-brewed espresso will have tight emulsification, meaning the CO2 bubbles are more tightly bound. This makes the foam more frothy, less watery, and longer-lasting. Better emulsification is a result of quality beans and proper brewing, which is part of the reason experts look to crema to judge the quality of the espresso.
The History of Crema
Although espresso has been around for over a hundred years, crema itself is a bit newer. Because crema is the result of high pressures, it did not come to be until the necessary technology was developed.
The first espresso machine, developed by Angelo Moriondo in 1884, used pressures of only 1.5 bars--far from the pressure needed for the espresso foam.
Many iterations of espresso machines were made after that, but it was not until 1948 until Achille Gaggia of Italy created an espresso machine that utilized enough pressure to create crema. At first, people were suspicious of the “scum” on top of their espresso. After Achille began to refer to this coffee foam as “caffe creme”, it began to be seen as a positive rather than a negative.
Achille Gaggia’s machine became popular across the world and led to the popularity of espresso drinks skyrocketing.
What Factors Contribute to Crema?
Although the brewing process is where the crema is actually formed, there are many factors that go into creating good crema.
Type of Coffee Bean
The first thing that really contributes to the amount and quality of crema is the type of bean used. Almost all coffee consumed around the world comes from two types of coffee beans: Arabica and Robusta. Arabica tends to have fruitier flavors and is generally regarded as tastier. Robusta is much bolder, more bitter, and has earthier notes. Robusta also tends to produce better, thicker crema. For this reason, it is the most popular bean to use for espresso (For More information on Arabica and Robusta click here).
How the Beans Are Processed
Due to varying climates, different regions process beans in different ways.
In hot, sunny regions such as Africa, after the coffee fruit is harvested the full bean (including the pulp surrounding it) is left out in the sun. The high temperatures and sunlight rot away the pulp until just the coffee bean is left. This method retains the most oil, which is the primary contributor to crema.
In less sunny regions such as South America, the pulp is washed off the bean and then the bean is left out to dry. This keeps some oils but is not as good as the previous method.
Finally, in regions without enough sun to dry the bean out in the open, the pulp is completely washed off the bean and then the bean is mechanically dried. This removes most of the oils and leads to worse crema.
How Much the Bean Is Roasted
Darker roasts bring most of the oils to the surface of the bean, where it is more likely to be lost during packaging and transportation. Darker roasts therefore produce less crema than lighter ones.
When the Coffee Was Roasted
Immediately after the beans are roasted, the oils begin to evaporate off the bean. The ideal amount of time varies a bit, but most coffee experts say that 4-5 days after roasting is the best time to make the coffee. Too soon and the excessive CO2 will mask the flavor of the coffee and prevent proper extraction. Too late and the bean will have lost its oils and will not produce espresso crema.
This is where experts look to the crema to see if the beans are freshly roasted.
Different machines produce different amounts and qualities of crema.
Lever-operated espresso machines produce the best espressos as the barista is able to control the brewing process. Manual machines do not rely on artificial pressures and temperatures.
Most automatic espresso machines aerate the coffee grounds during the brewing process which creates fake crema. They artificially add CO2 rather than letting the brewing process extract the CO2 from the bean.
Good vs. Bad Crema
Since some machines are able to fake crema, there has been a hot debate over how important crema is. While it used to suggest that the beans were fresh, and the espresso was created by a skilled barista, the ability of machines to fake crema has made it less important.
Crema is still important when made by manually operated machines because it signals quality brewing. However, when created by an automatic espresso machine, it does not really signal quality at all.
Is Crema Really That Important?
The presence of espresso foam used to signal a well-made, properly-brewed shot of espresso. Now that more advanced machines exist, it has lost some of its buzz.
However, some coffee aficionados still look to the presence and quality of crema to judge the quality of espresso.
For some people, they simply enjoy crema. The presence of a smooth layer of foam on their espresso can enhance their experience, especially when it is thick and frothy.
Whether or not crema is actually important is really up to you. Do you like a layer of foam on your espresso? Do you enjoy its taste? Well, if you answered yes, then you’d love crema. If not, no worries, simply scrape it off the top and enjoy your espresso--nobody will judge you, I promise.