Espresso Pressure Profiling and the Bezzera Strega

In the last 4-6 years, pressure profiling of espresso has been a cutting-edge technique to extract different interesting tastes out of espresso. The latest crop of the best commercial espresso machines all have pressure profiling capabilities: the Synesso Hydra, the La Marzocco Strada, the Slayer and others. These machines have high-tech approaches to change the pressure electronically during the shot. So, what is pressure profiling, and what does it accomplish?

Pressure profiling is the ability to vary the extraction pressure over time during an espresso shot. Typical pump-driven espresso machines extract at a constant 9 bars of water pressure during a shot. With pressure profiling, the pressure can be changed at will during the shot from 0-9 bars.

I haven’t had the opportunity to work with these machines myself, but the consensus that I’ve heard is that pressure profiling undoubtedly changes the taste of a shot. However, that change can be better or worse depending on what you do with the profile and the particular espresso blend you’re working with.

The only consensus that I’ve heard is that a gradual pre-infusion ramp to 9 bars almost always is a good thing, and then a declining pressure curve from 9 bars to a lower number at the end of the shot also generally improves a shot.

The funny thing to me about this consensus is that older lever machines have had both these characteristics for a very long time. Spring-driven levers inherently have a declining pressure curve: they typically have a peak of 9 bars and then decline to 4-5 at the end of the shot. Also, levers are usually plumbed in, and their design results in an initial pre-infusion at the water pressure of the line.

I’d worked with a Synesso Cyncra for years with Flying Five Coffee, and after Flying Five closed, I didn’t have an espresso machine for a few years while I tried to figure out a home machine that could measure up. After a two different Denver coffee shops switched away from their lever machines to Hydra’s and Strada’s, I was nostalgic for the lever taste that I had been enjoying. 

After lots of research and hand-wringing, I came across the Bezzera Strega, a “prosumer” lever machine. I’ve really enjoyed this machine, and I think the engineers at Bezzera are telling us something with its design.

Two features of the Bezzera in my opinion bring the Strega into the modern age and produce shots that vie with commercial pressure-profiled shots. First, they added a group-head heater to keep the temperature of the shot within about 5 degrees. This isn’t Hydra or Strada accuracy, but it is in the right neighborhood, and the results are great. With my old Synesso, I could taste differences as low as 2 degrees, and I can taste differences now with my Strega, so better temperature control would be a nice thing. But, what they’ve accomplished now is definitely good enough.

The second feature is a built-in vibration pump. Ostensibly, this pump allows the machine not to have to be plumbed in, but rather pull water from its built-in reservoir. But, in making the pump a 9 bar pump instead of putting in a 3 bar pump to mimic a typical water line pressure, I think the engineers at Strega are taking a cue from the pressure profiling world. The vibe pump creates a nice pre-infusion to 9 bars, which then switches over to the spring in the lever, starting at the same 9 bar pressure. The result is a nice continuous pressure curve that appears to match up with the pressure profiling consensus.

In a sense, with pressure profiling, we’ve learned some reasons why lever machines still have such a fanatical following today. It’s poetic that after some high tech development, the pressure profiling consensus found its way back to where espresso was born. The first espresso with crema was produced by Achille Gaggia with a lever in the 1940’s. 

Everything old is new again.

Advertisements

One thought on “Espresso Pressure Profiling and the Bezzera Strega

  1. I’ve handled la marzocco, synesso and slayer pressure profiling espresso machines.

    As well as the Bezzera Strega you had mentioned and I am really impressed with it.

    I’m glad that the writer is neutral and experience enough to be able to share the same observations I have as a real user.

    For users who can’t follow, please do a check on the popular pressure profiling settings.
    The pressure follows a pattern of low progressive pressure, reach a peak before declining.

    That’s actually a mimic of how lever machines work without the bell and whistles.
    Thus the PP machines are a reinvention on something already invented.

    There are still some differences in how they work.

    Pressure profiling machines are easier to work.
    Pulling down the lever takes some strength, compare to sliding the paddles.
    However that will also mean that such PP machines are more exorbitantly expensive.

    As the mechanisms have to change from a simple spring system to a pump that works artificially to mimic the same pressure movement.

    Imagine how a spring works.
    Now imagine a pump trying to mimic how the spring bounce back.

    In PP machines valves, pumps and gaskets work harder and wear faster due to changes in the pump movement.
    That’s like a gearbox in a car.

    For that it’s almost certain that spring lever machines are the hardiest genre of espresso machines.
    There’s no pump, it relies on the line of pressure from the water network in most cases.

    For the Bezzera Strega, it needs a pump to refill the boiler and it works for a mere 10 seconds.
    Even if it has a pump, the pump works only 1/3 of a regular cycle comparing any other machines.
    Meaning it naturally has a much longer longevity.

    Back to the cost, lever machines cost about 1/3 the price of a PP machine.
    Lever machines can last for an extremely long time and cost of its components are equally cheap.
    Compare replacing the spring with replacing the pump and controls.

    The cost of PP components are incredibly expensive as they are proprietary to their model.
    Due to its dynamics in how they work, it is almost a must to schedule for regular maintenance.

    Hope this sheds some light to any new owners.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s