Espresso grind size must be just right, but the finer grind is not necessarily more effective. Espresso making is a difficult skill to master for a long time. Even the best baristas fail from time time. Even more so if you're using superautomatic.
The grind size is the most crucial thing about espresso. To achieve the perfect espresso that has some sweetness, but is not too bitter, then you must find the ideal grind size.
Espresso Extraction
Around 28% of roasted coffee beans is water-soluble. This means that you can extract about 28% from the entire roast coffee bean. The remainder is cellulose as well as other plant materials that form the coffee bean's structure.
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Water needs help to dissolve soluble chemicals. Coffee beans can only be dissolved if they are heated in hot water. Coffee beans are very dense and complex, meaning that they are unable to pass through water easily. The flavor is absorbed by the water on its journey through.
For coffee to taste better it is necessary to enhance the amount of surface area on the beans. In this way, you can create gaps that allow water to permeate all the flavor. Coffee beans can be crushed to increase the surface area. The greater the surface area the greater the speed at which the reaction to water.
Water always extracts flavors in this sequence regardless of the methodemployed: acids and fats, then sugars, and finally the plant fibers.
We can't taste all the flavors of coffee, which is why we must be careful about the extraction. We do not want all the soluble matter in our cup. Many of these compounds are harmful, and we want to avoid extracting them.
Chemistry can be a powerful partner in this venture as bitter substances can be difficult to extract. If we stop extracting them in time, we'll only have the best substances.
Under Extraction
If you're not able to extract the right amount of soluble solids from the ground coffee, you'll get the cup is not fully extracted. Many of the flavors that provide an element of balance to your shot aren't extracted from grounds. Acids are among the most effective extraction agents of compounds, therefore shots that are not extracted could taste strangely salty and bitter, and lacking sweetness.
The extraction of coffee is directly related to the strength. To make a stronger cup of coffee, you can reduce the amount of water you drink. This is not the most ideal option, though feasible. The more coffee you extract, the more difficult it is to extract out all of the good flavors. The brew is saturated with saturates. The most important thing is that the coffee's compounds have different saturation levels as such, which allows us to take more of them off during the process of brewing. That's why when we brew a drip coffee to the espresso strength it tastes bad.
It's interesting to know that scientists, baristas and roasters examined coffee extraction , and found that too fine a grinding won't produce the best tasting cup.
The Grind Size and Extraction
The espresso machine is based on an air pressure pump that pushes water through the "puck" of coffee ground. This creates a rich and intense cup of coffee.
One of the most popular recipes for espresso is extra-fine grind that is around 20 grams for brewing a single shot of espresso. The purpose is to increase the coffee's surface area to water. This would result in more efficient extraction yield. Extraction yield refers to the quantity of solids that are soluble and are then incorporated into the final drink.
How Grinder Size Affects Surface Area
A study from the University of Oregon led by Christopher Hendon , computer scientist, and a competitive barista showed that most coffee shops strive to achieve an extraction yield of 17 and 23 percent. Higher yields of extraction can be bitter, but smaller yields make you feel bitter.
The team made thousands of espresso shots and came up with a mathematical formula to pinpoint the variables required to ensure a the same yield. They found that when coffee is ground to fine, the flow of coffee is at times too constrained and the shot gets over-extracted.
If you've grind your coffee too fine, you'll know it. If your coffee's grounds are too fine, the water can't pass through. Water can't pass through grinds that are tightly packed, because the puck is too small.
The problem lies in the size of coffee particles. An excellent analogy is the comparison between sand and rocks. The equivalent amount of sand rocks are equal in weight. If you pour water over the rocks, water will instantaneously go through. When you put the same quantity over the sand, the water will take a bit of time to move through the layer of sand.
Tampering can be a problem too. You can pack finely ground coffee better and the puck will be much smaller if you tap it. If you are tamping too hard, it can decrease the flow.
The team of researchers discovered that using a rougher grind and reducing amount of ground coffee per cup is better. This will allow for greater amounts of coffee to be brewed, which results in a richer and consistent coffee.
The Other Extreme
But, finer beans can cause the same problems as coffee with a coarser grind. It is only necessary to make slight adjustments to the grind size, these changes are unnoticeable to the naked eye.
Let's look at an extreme case in this case: If you choose for an espresso shot a medium grind, what is typically used for a drip coffee, your espresso will flow in 3 seconds. This is way too fast and will only extract acids. The coffee you drink will be under-extracted.
Espresso Variables and Extraction
All things equal roast degree has an impact on the extraction. A darker roast can make it easier to extract the exact same coffee bean.
A double shot of coffee should weigh between 14 and 21 grams. To ensure the highest quality outcomes, make sure you keep the quantity to a minimum of 1 gram from the number on the container.
Tamping can alter the flow speed of your coffee. This can impact the quantity of coffee you get.
The fines from a grinder are useful because they block the puck and aid in the flow. They provide a 20-second contact time for water with coffee grounds. The use of too much precision can block the puck, causing the shot to not flow.
Don't Be Strict
Make sure not to eliminate the spark of creativity from coffee making.
The great thing about coffee and the reason why people are so fond of it is the fact that you can't completely eliminate the human component. The scientific component that lets us make choices about the taste is important, and it helps us make decisions that will improve the coffee we drink, but creativity and personal taste are equally important.