The Science of Every Morning

(For a coffee lover at least)

As a tired and indecisive college student, I found myself dreading the complications within what I was considering that I write about. Sheepishly scouring the internet for something comprehensive to my interest, I neglected the answer in front of me — literally in a mug in my hand — coffee.

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The mighty concoction that has been semi-jokingly dubbed “god water” is something I would find the most interest in, scientifically speaking. Of course, that kind of humor seems to reveal a bit more than just respect; It’s a substance reliance that is shared with about 62% of Americans, and a proud member of this cult I am. However, consider how many within that 62% actually understand what is in their morning, afternoon, and nighttime cup of coffee? I barely understand how insurance works, nor do I have a firm grasp of what Tik Tok actually is — but I know how to make some good coffee darn it!

Though making coffee itself involves very few ingredients, there are many factors that go in to the process that make it good or bad. Similar to any practice of cooking, baking or creating, the quality of what you use make a major difference.

Let’s start with the beans. Coffee beans start out pretty similarly as green, unprocessed beans, but are roasted to roughly 3 different points: Light, Medium, and Dark. Based on what your experience with drinking non-flavored coffee, this might conjure sensations of Light roast being weak and watery and dark roast being strong and muddy. This is not the case.

Broadly speaking:

  • Light roasts tend to be fruity or a little floral.
  • Medium roasts are usually more balanced and even a little sweeter
  • Dark roasts approach a more bitter taste while maintaining some richness.

How does one extract these flavors and notes from their coffee every morning? The answer lies within the Chemistry and Physics that come within the brewing process.

In the whole bean coffee, there are hundreds of oils and even gases waiting to be extracted by a loving hand to be made in to a delicious drink. The composition of the bean is what gives each batch their unique flavor, dictating whether a coffee is more acidic, floral, or even has tasting notes of caramel. In order to properly extract these flavors and have them be present in your daily cup, we must consider the grind size of the coffee.

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As mentioned, there is a lot to be found in the coffee bean. The hot water you pour reacts with the ground coffee and allows the gasses and oils the gasses and solubles trapped within to be released. That same release is why you see the grounds create what seems like a foamy dome shape; that is the CO2 being released and pushing the grounds up. When you are working with a fresher coffee, more of these volatiles will be present and provide a more flavorful cup of coffee. Over time, the gasses will escape the bean, resulting in a duller tasting cup. Taking all of this in to account, the grind size remains equally important.

With a coarse grind, you have a lower surface area than you would a more fine grind.

In a coarse grind, water travels more freely between the ground and isn’t able to extract quite as much. In this case, your coffee would be on the weaker side in terms of taste and even seem watery. In order to extract a similar amount to what you would in a finer grind, you would need increase amount of time the water is in contact with the ground coffee. There are brewing methods that utilize this, known as immersion brewing.

In a finer grind, you have a higher surface area.

Here, it takes more time for water to travel all the way through and allows for a higher rate of extraction. However, if the grind is too fine, your coffee would take too long top brew and would end up tasting bitter due to over-extraction. A finer grind would be used in espresso; the pinnacle of both strong and flavorful coffee. Espresso is able to maintain both strength and flavor because it uses pressure and its relation to temperature to extract solubles. As we might have discussed in our science classes, we understand that as pressure increases, temperature also increases. Espresso machines run 90–96C (195–205F) water through the ground coffee, with its pressure typically reading about 131 psi. Compared to pour over coffee using water being gently at 89–94C, the difference is something you can taste.

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Touching back on the different roasts, they also react differently to various temperatures as well.

While the same bean roasted at different levels will share some characteristics, they may have totally different tasting notes. The heat from roasting does end up allowing some of the oils to evaporate, and the gasses within will also change.

Coffee can be prepared in many different ways with even more variables that will affect how good (or bad) your coffee will end up tasting. At the same time, the preference in process will change from person to person. Do yourself and your coffee the courtesy of experimenting with different variables like the scientist we all secretly are.

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