Paolo Dalla Corte tells us his point of view on espresso machines

May 20, 2021

Moving on to coffee extraction systems, we want to dedicate an entire chapter to espresso machines – no one better than Paolo Dalla Corte could introduce us to this topic!

What are the characteristics that a coffee machine must have to extract the best espresso?

“I’d like to start by saying that in my opinion, there is no perfect cup of espresso. Evaluating coffee can be in great part objective from a technical point of view, but there is also a very subjective component that makes the evaluation personal. That said, to list the main features that a coffee machine must have to extract any type of coffee in the best way possible, we must first see what does an espresso machine bring into the cup.

Unlike other extraction systems, espresso machines apply thermal energy and mechanical energy to the water. To ensure the best extraction, machines must have thermal flexibility to adapt to any type of coffee and roasting on the market. The higher the temperature, the more soluble parts of the coffee are released into the water. Once we’ve found the right point of extraction - that is, the right point of coffee solubility proportional to the amount of water - this variable must be consistent. It seems like word play, but if we want this result to be repeatable hundreds of times throughout the day, the temperature must be as steady as possible, otherwise we risk not having the same result any given cup. And once the barista finds his perfect cup, he wants this perfection to be repeatable.

The second energy we apply is water pressure. Every time we brew coffee, we operate a motor pump that generates pressure. It’s been found that the ideal pressure to extract an espresso lies between 8.5 and 9.5 bar. We can almost say that espresso isn’t a proper drink, it's the elixir of an emulsion.

These are the foundations of a coffee machine, but experience and evolution has highlighted another important variable - pre-infusion. A feature already known in the 1960s and then underestimated for several decades. Only recently, with the coming of digital and manual flow regulators, has this phase been re-evaluated as an additional variable that can be set for espresso extraction. At the same temperature and pressure, pre-infusion allows you to explore in more detail all the organoleptic properties of a single origin or a blend.

This phase is fundamental, as it prepares coffee for the actual extraction: depending on the water flow we are going to apply, pre-infusion allows us to wet the puck faster or slower and apply pressure for a longer or shorter amount of time. If done correctly, we can achieve different aroma intensity and body. And like all variables, once the correct setting has been found there has to be the possibility of repeating it over time. "

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Paolo Dalla Corte tells us his point of view on espresso machines