An Overly Simplified Explanation of How Coffee is Made

When making coffee, what is actually happening within that concoction of coffee grounds and hot water?

First, lets briefly see what needs to take place leading up to the brewing process.

Coffee beans are roasted anywhere from light to dark. Next, the whole beans are ground into tiny particles that increase the surface area of the bean up to 6X (depending on grinding method).

TIP: Once the coffee bean is ground it immediately begins to loose CO2, aroma, flavor and antioxidants. So act fast if you want the best tasting coffee.

Once roasted and ground, the coffee beans still contain over 1,000 compounds, chemicals, and elements essential to the taste and quality of the final coffee.

So, how do we extract the compounds, chemicals, and elements that we want and at the same time keep out the ones that we do not want? Simple. Hot water and a filter.

There are many, many components that go into brewing a cup of coffee, but rarely does it go beyond simple solubility rules and the separation of liquid and solid.

Of the thousands of compounds, chemicals, and elements I mentioned earlier, we really only care about a handful of them when talking about what we want in our final product.

These include:

Caffeine (obviously), trigonelline, chlorogenic acids, soluble fiber, carbohydrates (sugars), protein, peptides, and free amino acids, minerals, and lipids.

For more detail on each one of the above read about coffee constituents here.

The extraction of the above begins the very moment water reaches the coffee grounds and continues as it trickles all the way through the filter and into your cup.

All of the above can be separated from the ground coffee because they are water-soluble. This means that they dissolve into the water and use the water as transport into your mug.

Once all of the water has passed through the filter, the “leftovers” that remain are essentially insoluble waste products. This is the physical separation of liquid from solid. The filter also serves to prevent lipids (fats) from getting into your coffee. This happens due to the fact that most coffee filters have lipophilic (lipid-attracting) membranes that don’t let the fats through.

TIP: This is the reason why espressos contain a slightly higher fat concentration. They don’t use paper filters that prevent fats from getting into your coffee.

So that’s basically it. The stuff that we want in our coffee is extracted from ground coffee beans by means of solubility i.e. dissolving them into hot water. The liquid containing the dissolved “goods” is then filtered through a coffee filter to separate it from the solid leftovers. After all of this has been completed, the liquid solution we have remaining is what we, ladies and gentlemen, call coffee.

Links:

Coffee Chemistry

Chemistry of grinding coffee