We’ve had our Vesuvius Espresso Machine for a few weeks now, and have really enjoyed getting to know it. We covered its key attributes in a previous post. Now it’s time to get into the nitty-gritty of Vesuvius’ main game: pressure profiling.
While the machine has the capability to program up to seven steps in a profile, in this early stage of experimentation we thought it best to keep it to a maximum of five. We set up 5 profiles that would best demonstrate the effects of pressure variation on the in-cup flavour.
As a point of reference, the first profile was set to a standard 9-bar pressure extraction throughout the entire shot. The machine’s gear pump is similar to a vibratory pump in that it slowly ramps up to the required pressure.
The resulting shot from our Lovejoy Espresso blend was balanced with medium acidity and a lingering aftertaste. Running our single origin Brazil Minas Gerais beans through this profile brought out rich nutty and bittersweet chocolate notes, while Ethiopian Yirgacheffe was fruity with sharp lemon acidity.
For Profile Number 2 we mimicked line pressure pre-infusion by setting the pressure to just 2 bars for the first 6 seconds of extraction. The rest of the shot was extracted at 9 bars. The coffees all had the same basic flavor profile but with a little more crema, increased acidity and pronounced bitterness in the aftertaste.
Our third profile consisted of 20 seconds extracting at 9 bars and followed by a reduced pressure of 6 bars for the remainder of the shot. For Lovejoy, the overall flavor was smooth and sweeter, but there was some astringency in the aftertaste. For the single origin beans this profile brought more balance to the cup by rounding out the acidity.
Next we took the previous two profiles and combined them to produce a profile that both pre-infuses and reduces pressure at the end of the shot. This certainly increased the complexity of the shots, but they tasted a little under-extracted. As the overall pressure of the shot was lower than usual it would have been more beneficial to extend the extraction time past 30 seconds to extract maximum goodness out of the beans.
For our last profile we gradually stepped the pressure up during the course of the shot, all the way up to 10 bars before easing off at the very end. The actual pressure briefly went above 11 bars, as the Vesuvius tends to briefly overshoot the set pressure before hitting the right spot.
The resulting espresso shots were darker in color with more crema and increased flavor intensity. For the Lovejoy, it was just a little too much. It killed the sweetness and brought a rough bitterness to the cup. On the other hand for the Brazil and Ethiopian single origins this profile brought out more complexity and gave us a well rounded espresso.
The moral of the story is that no single pressure profile is right for every roast. What works for one bean may not bring out the best of another. Through experimentation and with a touch of creativity you will soon find the sweet spot of each and every roast.