Espresso should be grind to a fine point but not too fine. Making espresso has been a mystery at some degree. Even the most skilled baristas can make mistakes. If you're using an automated it's even worse.

The grind size is one of the most important things about espresso. A proper grind size is crucial to get a perfect espresso with sweetness and not too bitter.

Espresso Extraction

Around 28% of roasted coffee beans is water-soluble. This means you can extract approximately 28% from a whole roasted coffee bean. The remainder is mostly cellulose and plant stuff which makes up the structure of coffee beans.

Full story - Discover more here about espresso extraction

Water needs help to dissolve soluble chemicals. When you place coffee beans into hot water, they will only melt the outer layer. The coffee bean's structure is extremely dense and complex and water is unable to move through it easily. The water can hold every flavor.

Coffee tastes better when you increase the bean's surface area. In this way, you can create gaps that allow water to permeate all the flavors. Coffee beans can be crushed to increase the surface area. Coffee beans react faster to water if they have greater surface area.

Water extracts flavor compounds in the following order, regardless of how it is made acidic substances, fats, sugars, then plant fibers.

Some coffee's flavors are good, so we have to control the extraction and stop it before the bitter compounds start to disintegrate. We don't want every soluble matter to get into our coffee. A lot of these compounds are not desirable, so we avoid removing them.

Chemistry is an excellent partner in this endeavour as bitter substances are difficult to extract. If we stop extracting them at a certain time, we get only the good stuff.

Under Extraction

It is possible to get a cup that has too few solids soluble in the coffee grounds. A lot of the flavors that balance your drink remain unextracted from the ground. And because acids are the substances that extract the fastest, an under-extracted shot may taste sour, weirdly salty and without sweetness.

The strength of a coffee is directly in relation to extraction. If you're looking to make a strong coffee, you can utilize less water to boost the strength of the cup. Although it is possible, it isn't the best choice. The greater the amount of coffee you extract, more difficult it will be to extract all of the good flavors. The brew has saturates. It is important to note that the different levels of saturation of coffee's components can be utilized to extract more. This is the reason why a cup of coffee which has been brewed to espresso strength is a sour taste.

What's interesting is that a group of baristas, roaster, and scientists looked into coffee extraction and discovered grinding too finely doesn't make the most delicious cup.

The Size of the Grind and Extraction

An espresso machine relies on the pressure pump to push water through a "puck" of coffee ground. This results in a rich and intense cup of coffee.

The most well-known recipe for espresso is extra-fine grind settings around 20 grams to brew a single espresso shot. This is done to increase the coffee's surface area, which is then converted to water. The result is an increase in extraction yield. The yield of extraction is the proportion of soluble solids which are eliminated and end up in the final beverage.

How Grind Size Impacts the Surface Area

An experiment conducted by Christopher Hendon, an computational chemist as well as a barista from a competitor, has revealed that coffee shops strive for extraction yields of between 17 and 23 percent. Lower extraction yields taste sour high yields taste bitter, while higher yields are too bitter.

The team prepared thousands of espresso shots and devised a mathematical model to determine the factors needed for a consistently high yields. The team learned that coffee grinds too fine can lead to restricted flow and over-extracted shots.

If you've ever ground your coffee too fine, you'll know it. If your coffee grounds are too fine, water cannot pass through. It is impossible for water to pass through tightly packed coffee grounds because the puck is too small.

The issue lies in the size of coffee particles. An excellent analogy is the comparison between sand and rocks. The identical amount of sand and rocks are equal in weight. It is possible to pour water over the rocks and it will instantly flow through. It takes a while for the water to get through the sand layer If you pour the exact amount of water on the rocks.

The other part of the problem is process of tamping. Finely ground coffee better , and the puck will be more compact if you tamp it. This will limit the flow more, if you tap too very hard.

The study team found that using a slightly rougher grind and reducing amount of ground coffee per cup is better. This allows for greater amounts of coffee to be made, and results in a deeper and regular the brew.

The Other Extreme

But, finer beans can be as problematic as coffee that is coarser. This can be done through very small adjustments to the size of the grind.

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

Espresso Variables and Extract

All things equal roasting degree can have the same effect on extraction. A coffee bean is more efficient in extraction when it's roasting dark , in contrast to lighter roasts.

Double cups of coffee ought to weigh between 14 and 21 grams. For the best result, ensure that the measurement is within one gram of the number on the container.

Tamping can affect the flow rate of the coffee. This in turn determines how much ground coffee is removed.

The fines of a coffee grinder are beneficial because they block the puck and help with the flow. The coffee grounds as well as the water have a contact period of 20 minutes. The use of too much precision can block the puck, causing the shot to not flow.

Do not be too strict.

Make sure not to remove the fun from the coffee making.

The appeal of coffee and why people are so passionate about it is because you can't eliminate the human element. It is the scientific component which allows us to make choices regarding flavor. We can utilize it to improve the quality of our coffee. But , of course, personal taste are equally important.