After roasting, we now have the coffee beans that we know and love, but our chemistry journey is not over yet. Coffee’s full potential is brought to life through the processes of grinding and brewing. These steps are where the carefully developed flavors and aromas are extracted and transformed into the beverage we love.
The science behind grinding and brewing is just as important as the earlier stages of coffee production, if you want a good cup of coffee that is. Your coffees grind determines the surface area of the coffee particles, which directly impacts how water interacts with the grounds. At the same time, temperature, pressure, time, and water chemistry all play a part in warming your mug with a delicious beverage!.
Grind Size and Its Effects
Grind size is a key factor in your coffee brewing and the method of brewing that you choose. Different grinds affect the surface area of coffee particles exposed to water.
Finer Grind
A finer grind, used in concentrated coffee brewing processes like the Espresso Machine or the Turkish Pot, increases the surface area of the coffee particles that water can interact this. This higher surface leads to a higher extraction yield, and an increased of the total dissolved solids in the water. It is commonly said that an espresso grind should be fine enough to stick to your finger, this is because the finer the grind the more soluble the coffee particles are in water creating a more concentrated brew.
Fine grinding methods enhances the release of polyphenols, a type of antioxidant, due to the increased diffusion during brewing. Some argue that this finer grind can actually enhance the health benefits of coffee, as we see polyphenols in many fruits and vegetables.
Coarse Grind
A coarse grind, used in many common brewing methods like a Pour Over, a Drip Machine, and the French Press, reduces the surface area leading to a lower extraction yield. To combat this lower solubility rate, most coarse brewing methods have an increased amount time the grounds brew for. Contrast to the finer grind getting a large amount of flavor from the total dissolved solids, coarse grind methods allow for heat and time to extract oils from the coffee beans to make a smoother brew.
A coarse grind over long periods of time (20+ hours), the method to make cold brew, has been shown to yield higher total phenolic content leading to a sweeter and less acidic flavor.