How Does Grind Size Affect Espresso?

Espresso grind size should be just right, but too fine is not better. Espresso making has been a challenge to master over many years. Even the most skilled baristas are not perfect from time to occasion. If you use a super-automatic it's even more difficult.

The size of the grind is the most important thing about espresso. A perfect grind size is necessary for getting a shot with sweetness , but not overly bitter.

Espresso Extraction

Coffee beans that have been roasted are approximately 28% water-soluble. This means you will extract around 28% from the entire coffee bean. The remainder is mostly plant stuff which makes up the structure of coffee beans.

Full story - espresso extraction

Water needs help to dissolve soluble chemicals. If you drop coffee beans into boiling water, they will only melt the outer layer. Coffee beans are very dense and complex, meaning that they cannot be dissolved easily. The water is able to absorb every flavor.

For coffee to taste better, you need to enhance the amount of surface area on the beans. This leaves holes in the beans, which will allow water to penetrate all the flavors. Coffee beans are able to be ground to increase the surface area. Coffee beans react quicker to water if they have larger surface areas.

Water always extracts flavor compounds in this order regardless of the methodused: fats and acids, then sugars and finally plant fibers.

We don't have the ability to taste all flavors of coffee, therefore, we have to be able to control the extraction. We don't want every substance that is soluble to go into our coffee. A large portion of those substances are harmful, and we'd like to avoid removing the undesirable compounds.

Fortunately, chemistry works with us to solve this problem, as most of the bitter compounds are hard to extract. Therefore, if we stop extraction before and only extract the good stuff.

Under Extraction

You'll get a cup with too little soluble solids in the ground coffee. Many of the flavors that give the balance of your shot aren't extracted from grounds. Acids are the compound that release the most quickly, an unextracted shot could taste sour or weirdly salty and without sweetness.

The strength of a coffee is directly in connection to extraction. To get a strong cup of coffee, reduce the quantity of water that you consume. This is not the most ideal option, though possible. The more coffee you extract, the harder it is to extract all of the good flavor. The coffee brew contains saturates. The reason for this is that the coffee's compounds have different saturation levels as such, which allows us to extract more of them during brewing. This is the reason a coffee that is brewed to espresso strength tastes terrible.

It's fascinating to learn that baristas, researchers, and roasters looked into coffee extraction and discovered that grinding too fine won't produce the best tasting cup.

The Size of the Grind and Extraction

An espresso machine uses an air pressure pump that pushes water through the "puck" of ground coffee. This creates a rich and concentrated cup of coffee.

Extra-fine grind settings of around 20 grams are a common way to make espresso. This lets you brew one shot. The reason is to increase the coffee's surface area by water. This could result in increased extraction yield. Extraction yield is measured by the amount of solids that disintegrate and end up in the final drink.

How Grinder Size Affects Surface Area

A study from the University of Oregon led by Christopher Hendon , who is a computational chemist and barista with a winning streak showed that most coffee shops strive to achieve an extraction yield of 17 and 23 percent. Lower extraction yields taste sour high yields taste bitter, while higher yields are too bitter.

They prepared thousands on thousands of espresso shots and then came up with an algorithmic model to pinpoint the variables needed to get the same yield. The team realized that coffee grinds too finely can result in reduced flow and excessively extracted shots.

It happens when you grind your coffee to fine. Water just doesn't pass through the coffee grinds if the grounds are too delicate. The puck is too small and water can't pass through the coffee's densely packed grounds.

One of the reasons is the size of the coffee particle. A good analogy would be the contrast between rocks and sand. You can have the same amount in terms of weight. You can pour water onto the rocks and it will immediately pass through. If you put the same amount on the sand, it will take some time to pass through the sand layer.

The other aspect of the problem is the process of tamping. Finely ground coffee better and the puck will become smaller if you tamp it. This will limit the flow further if you tamp too heavily.

Research team discovered that a more coarse grind and a smaller amount of coffee per shot are more effective. This leaves some extra room in the coffee bed, creating a larger coffee brewing process that is more even and even.

The Other Extreme

However, finer coffee could be as problematic as coffee with a coarser grind. The only thing you need is a few adjustments to the grind size, these changes are unnoticeable to the naked eye.

Let's consider an extreme instance: If you use for an espresso shot a medium grind, what is typically used for a drip coffee, the espresso will be ready in three seconds. This would be way too fast, and it could only extract acids. Your coffee will be extremely under-extracted.

Espresso Variables and Extract

The roast degree can affect the extraction, but it's not the only factor. The same coffee bean will extract easier when it's roasting dark , in contrast to lighter roasts.

Double cups of coffee should weigh between 14 to 21 grams. For best results, be sure to keep the measurements within one gram of the amount in the cup.

Tamping will affect the rate of flow of your coffee, which in turn determines how much ground coffee is extracted.

The fines that come from a grinding machine are useful because they block the puck, and also aid in the flow. The coffee grounds and water have a contact time of 20 minutes. However, too much precision can cause the puck to become blocked, and the shot will take a long time to get through.

Don't be too strict

Be sure to not take the creativity out of coffee brewing.

The appeal of coffee and the reason that people love it so much is the fact that you can't completely eliminate the human component. The scientific element which allows us to make decisions about flavor is crucial, and it lets us make choices to enhance our coffee, but creativity and personal taste are equally important.