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Brewing basic concepts: What are we actually doing in coffee brewing?

“Put your paper filter into the dripper, weight and grind your coffee, start pouring water...”. I guess many people start learning how to brew coffee by watching videos or brew guides with lots of pictures, just like me. It is a great start; we learn and accept things easier by watching videos then reading abstruse and unfathomable sentences. But the question is, do you understand the reasons behind every step? In this series, I will try to explain some common concepts based on my understanding so you may get some sense of what are we “brewing”. This article is about the fundamental concept: what are we actually doing?

You might see lots of coffee brewing equipment every day such as espresso machine, drippers, siphon, no matter how different their working principles are, they are doing the same thing:

“Use water as solvent to dissolve solubles in coffee beans”

We can’t just brew green coffee bean because the content and structure of green bean is not suitable for brewing and drinking (and it smells like grass). When green coffee bean is roasting, there are some chemical changes happened inside the bean (Maillard Reaction, Strecker Degradation and Caramelization of Sugars, you could do some research if you interested.) and when the roasting finished, the content and structure inside the bean was changed and now it is good to start brewing.

But wait, if water can dissolve solubles in coffee bean, then why don’t we just put the whole beans into water and let them stay forever. Why we need to grind and use different equipment? The coffee bean cannot completely be dissolved by water and not all content in coffee bean has good flavour. See below:

Theoretically, the longer coffee bean contact with water, the more solubles will be dissolved. So how can we try to get more good flavours and avoid the bad flavours, the main point is to control the contact time. We will talk about that in future articles.

Other articles in this series:

- Brewing basic concepts: Grinding coffee and grind size

Brewing basic concepts: Working principle of brewers