Like coffee and chromatography?

Like coffee and chromatography? Fun fact: brewing a perfect espresso is a lot like doing chromatography with broken fraction collector, where you only have one tube to collect extract. Good espresso requires some tuning, but let’s simplify for clarity.

For a double espresso, take 14 g of ground coffee and extract it with a 1:2 brew ratio – that is, 28 g of water – over 30 seconds. This corresponds to a flow rate of roughly 60 mL/min. Assuming a homogeneous distribution of coffee particles (as should be the case with a good grinder), adjusting extraction volume and time effectively determines which molecular fractions are extracted.

Let’s oversimplify these into two fractions: one sour and one bitter (see Figure 1). At a 1:2 brew ratio, we collect some sour fractions and part of the bitter fractions, producing a balanced espresso. At 1:1, we extract mostly sour fractions; at 1:3, we extract too many bitter fractions. In both cases, the balance is lost, preventing us from fully tasting the coffee’s flavors.

So, ideal espresso is like chromatography: you control volume, flow rate, and rely on your sensors  – nose and mouth.

P.S. This is what happens when you can’t switch off your scientific analytical mindset while learning a new hobby.

P.S.S. Now I am thinking whether I should build small fraction collector and analyse separated fractions? 🤔