During our training for new baristas, we often start with a small experiment. We pull a double espresso on our Marzocco, but instead of pouring everything into the same cup, we let the first third flow into one cup, then quickly switch to a second cup for the next third, and finally do the same to put the last third into a third cup.
Next, we taste each one. The results tell us a lot about what it takes to make a great coffee – or to ruin one!
You can easily guess the first difference: intensity. The first coffee hits you hard, the last is a bit weak, and the second is, of course, somewhere in between. But what is more surprising is that the tastes are also clearly different, as if they are not the same coffee at all. The punch of the first comes not only from the intensity but also from a high level of acidity. Perhaps it’s a pleasant acidity, like that of fresh fruit, but it would be a bit harsh for most people. On the other hand, flavors and aromas are largely absent from the last one. It is milder, but a bit flat and uninteresting.
The reason is that coffee beans are made up of many different organic components – sugars, proteins, organic acids, volatile aromatic compounds, etc. The most soluble elements come out first, like the organic acids that are very present in the first third of the espresso. The last third contains few highly soluble elements, as they have already come out, but more less-soluble elements that took longer to fall into the cup.
So what? you might say! Well, regardless of the science, there is an important lesson to be learned from all this for anyone making coffee: the extraction time, or the time it takes for water to flow through the coffee, makes all the difference in terms of taste. You can take the best coffee in the world, perfectly roasted, and use an espresso machine that costs an arm and a leg. But if the extraction is too fast or too slow, the result can still be unpleasant – too acidic, too bitter, lacking flavor or body.
Which opens up a whole new topic of discussion: how to control extraction time! The question is simple but the answers are numerous and complicated. Fortunately, there is a very good starting point.
The Grind
All other things being equal, a finer grind will be more resistant to the flow of water, which will slow it down. Conversely, if you want to reduce the extraction time, use a slightly coarser grind.
Then, have fun! Try different grinds and taste the difference in the cup, until you achieve the balance that you like best.
That is what good coffee shops do every day!
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