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How Grind Size Affects Espresso Extraction

Jan 10

Espresso grind size shouldn't be too fine. Espresso making has been difficult to master for many years. Even the most skilled baristas have made mistakes. It's worse if you use a superautomatic.

One thing that is consistent though, is the espresso grind size. You need the right grind size to ensure a perfect shot.

Espresso Extraction

Water-soluble coffee beans contain around 28%. You can extract around 28% of the whole roasted coffee beans. The remainder is cellulose and other plant material that make up the coffee bean's structure.

Water needs help to dissolve soluble chemicals. If you throw coffee beans in hot water, they only dissolve the outside layer. The structure of the coffee bean is extremely dense and complex. Water can't penetrate it easily. The water that passes through the coffee bean collects all the flavor.

You can make coffee taste more delicious by increasing the beans' surface area. This will create air pockets that allow water to enter the coffee beans and enhance their flavor. By grinding coffee beans, we can increase the coffee bean's surface area. The more surface area, the quicker it reacts to water.

Water always extracts flavor compounds according to this order, regardless what method it uses: fats and acid, then sugars, then finally the plant fibres.

Acids, and fats, are the first compounds taken from coffee. Acids are the most basic compounds, and they give coffee a sour flavour. This makes it easy for water to dissolve them in the coffee. Many of the light aromatics, for instance the the floral an d the fruity flavors are extracted at this moment. It's the final cup that gives coffee its flavor.

Not all of the coffee's flavors are good, so we have to control the extraction and stop it just before the bitter compounds start to break down. We do not want all soluble matter to go into our cup. Many of these compounds can be harmful and we don't want to extract them.

Chemistry works well with us because bitter compounds are more difficult to extract. We can stop extracting them in time so that we only get the good stuff.

However, if we don't stop the extraction in time, we obtain an over-extracted cup of coffee.

Under-Extraction

Under-extraction is when the coffee doesn't contain enough soluble substances. A lot of the flavors that bring balance to your shot are left unextracted from the grounds. Acids are the compounds that can extract the most quickly, which means that a shot with too much acid can taste weirdly salty or without sweetness.

The extraction of coffee is directly related to the strength. You can use less water to make a stronger cup. Although it is possible, this is not the best option. The more coffee you extract, the more difficult it is to extract out all of the good flavors. The brew will saturate. More important, the saturation point of coffee compounds can vary. This allows us to extract more from them during brewing. Because of this, a drip coffee that is brewed to an espresso strength does not taste good.

Espresso extraction will be affected by the size of your grind. Grind size is the most important variable for espresso brewing.

What's interesting is that a group of baristas, roaster, and scientists studied coffee extraction and discovered that grinding too finely won't yield the most flavorful cup.

The Grind Size, and Extraction

A pressure pump is used to force water through the "puck" of ground espresso. This produces a thick and concentrated coffee.

Extra-fine grind settings at around 20 grams is a very popular method to make espresso. This is done to increase the coffee’s surface area to water. This should result in a higher extraction yield. Extraction yield refers to how much of the soluble solids are removed and what end up in final beverages.

How Grin Size Affects the Surface Area

A University of Oregon study, led by Christopher Hendon (a computational chemist) and a competition barista revealed that most coffee shops seek an extraction yield of between 17-23 percent. The lower extraction yields are bitter and taste more like sour than the higher ones.

The team brewed thousands of espresso shots and developed a mathematical model to pinpoint the variables required to get consistent yield. They discovered that coffee that has been ground too fine causes a reduction in flow, which can lead to an over-extracted shot.

Coffee that is too finely ground will not be brewed. Water just doesn't pass through the coffee grinds, if the grounds are too fine. The puck is too compact, and water will not pass through the densely packed coffee grounds.

The size of the coffee particles is part of the problem. You can compare sand to rocks. The same quantity of each is determined by its weight. The rocks will absorb water if you pour it on. The water will take a while to reach the layers of sand if it is the same volume.

The other part of the problem is the tamping. Tamping finely ground coffee will allow you to pack it better so that the coffee puck is compact. If you tamp too hard, this can reduce the flow.

Research team discovered that a coarser grind and less coffee per shot are better. This results in a more full and even brewing process.

The Other Extreme

However, coarser coffee is just as problematic as finer coffee. Only very minor adjustments are needed in the grind size.

Let's use an extreme example. A medium grind is usually used for a drip espresso. Your espresso will pour in about 3 seconds. This would not extract the acids, as it would pour too quickly. You will find that your coffee is very under-extracted.

Espresso Variables & Extraction

Everything else being equal, the roast degree will also have an impact on the extraction. It will extract the same coffee bean more efficiently if it is roasted darkly than if it is roasted lighter.

A double dose of coffee should not exceed 14 grams. To get the best results, keep the amount within 1 gram of the number printed on the container.

Tampering can affect the flow rate of your coffee which will in turn impact how much coffee you extract.

Because they clog up the puck, the fines of a grinder are great because they help to improve the flow. They allow water to contact the coffee grounds for 20 seconds. The shot may not flow if there is too much finesse.

Don't be too rigid

Do not let the creativity go out of coffee brewing.

A human component is one of the best things about coffee, and it's why people love it so much. While the scientific component is essential in making decisions about flavor, it also allows us to make choices to improve our coffee. However, creativity and personal tastes are equally important.

This article was syndicated from Daily Preston UK News.