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.

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Scales

I’ve been using scales for brewing coffee for years. My friend who owns a bakery first clued me into this way of controlling not only the amount of grounds, but also the amount of water that go into a particular brew.

At first glance, it would seem like measuring water with a scale is overkill: it’s easy to measure water with a cup measure. However, when brewing drip/pour-over with fresh coffee, the bloom of the coffee prevents you from being able to accurately measure the water going into the brewing vessel. Same deal with espresso: the crema in your shot expands the volume so that you can’t measure it effectively. So, scales to the rescue: they precisely measure the amount of water regardless of bloom or crema. 

For pour-over or french press, I’m typically brewing for just myself. For a French Press, I measure out 14g of beans and then put a scale underneath the press. I then pour in 210g of water. How did I arrive at these numbers? I started with how much coffee I like to drink in the morning: about 7-ish ounces. I then used a 15:1 brewing ratio of water to grounds and converted it all to grams. This concept of a brewing ratio is a useful one: you can use it to find what ratios you enjoy, and then scale up or down the amount of coffee you like to drink.

For espresso, I’m even a bit more obsessive than most with scales. I use them at the grinding and brewing end. For my grinder, I measure out a bit more than 18g of beans, and then after I grind it, I tare it down to 18g precisely. Why take this extra step? It’s because of my grinder: despite my best efforts, some grinds tend to get trapped, and so the amount that comes out varies a decent bit.

Then, when brewing, I put a scale underneath the cup I’m pulling the shot into, and measure the amount of espresso in the shot, which is 1.5 oz. This isn’t the usual approach: I’ve seen many coffee shops that do a very good job pull shots into a measured shot glass and measure the shot by volume. While this is a pretty good approach, it’s inaccurate because of the crema expanding the shot and making it difficult to measure. Also, it means that you have to pour the espresso from that shot glass into the drinking cup, and in that process some of the precious crema is left behind in the shot glass. Popping a scale underneath the cup, and pulling the shot right into the cup gives you both precision and collects every morsel of crema.

Is this obsession with precise measurement really necessary? That depends. For me, the precise control of the brewing process provides solid platform that greatly increases my enjoyment of quality coffee. 

Here’s how I think of it: accurate brewing measurements create a technical foundation for the artistic and culinary aspects of quality coffee. Given that solid foundation, it’s fun to explore the possibilities of different coffees and go exploring for different tastes.

Bezerra Strega

Last December, I bought a Bezerra Strega home espresso machine for my office after not having an espresso machine for a number of years. Back with Flying Five Coffee, we had a Synesso, which I consider one of the best commercial espresso machines in the world, and I just couldn’t bring myself to go backwards to older less precise machines.

The Strega has rescued me from the espresso doldrums. It’s a “prosumer” lever machine that combines the old-school lever with some new-school features that gives temperature-stable commercial machines a run for their money.

The thing I really enjoy about the Strega is that it enables you to just use the machine and enjoy the benefits of great espresso without needing to go overboard in technical details. This is something that I’m very prone to do. In just using the machine normally, you’ll be reaping the benefits of good-enough temperature stability and modern pressure-profiling of the extraction.

If you read the Strega thread on home-barista, you might be intimidated about the technical detail discussed there and think that it’s complex to learn and use. I don’t think this is the case. Even when I was just starting out with the Strega, I had immediate good results with it.

Initially, you can just turn on the Strega, let it warm up for 20-25 minutes, grind, tamp and extract. The Strega is always in the right temperature ballpark for good extraction, and just “going for it” and pulling shots works very well. You’ll have great espresso pretty much immediately.

But, as always with espresso, careful attention to detail always improves things. I’ve learned some things over the last 9 months from reading the home-barista thread and from experimenting. Here’s how I use my Strega now:

First, I turn it on just 10-15 minutes before I want some espresso: it heats up really quickly, which I absolutely love. There’s nothing that bothers me more than waiting around when I’m ready for espresso!

Once I hear a short hiss from the machine (which is the vacuum breaker sealing), I wait about a minute more and then pull about 10 seconds of water by pulling the lever down, and then I raise the lever very slightly to stop the vibe pump. I do this to hold some of the  hot water up in the piston to warm it up. This is optional, and is just a time saver: it cuts a decent bit of time off the warm-up time.

Then, I grind and tamp 18g of espresso at 35 lbs. pressure. Before I put the portafilter in, I do a very short cooling flush with the lever: just long enough to release any pressure that’s built up in the line. Then, I put the portafilter in and pull the lever all the way down.

This engages the vibration pump, which fills the piston with water and starts pre-infusion. I let this go until the sound of the vibe pump changes, or espresso starts to drip out. Then, I release the lever and let it extract.

You can steam milk at any time: the Strega is a heat-exchanger.

For me, the result is quality espresso that I really enjoy. I’ve even been having fun pulling the same espresso from the Strega that I can get at shops in Denver out of Synesso’s and comparing the taste differences. Amazingly, the Strega stays neck-and-neck with its commercial counterparts.

Bodum Pavina Glasses

I’ve been using Bodum Pavina double-walled glasses for a number of years now. Actually, we sold these way back with Flying Five Coffee, so that means I’ve been using them since at least 2007/2008. I think these glasses are great, and not just because they look cool.

They’re hand-blown double-walled borosilicate glass. The obvious advantage of the double-walled glass is that it insulates the hot coffee from your hand. While this is a fantastic feature, I think there’s another more interesting advantage to this: you can control how the coffee cools.

One of the many things I love about drinking single origin coffees is how the flavor changes as the coffee cools down. With a “normal” cup, this is a passive journey. With the double-walled glasses, you can control the cooling somewhat. What I like to do is to blow across the top to cool the coffee and taste as I go. When I find a taste that I’m particularly enjoying, I’ll stop and pause for a while, and the insulating double-walled glass lets me linger on that taste for a while. Then, I’ll go find another one.

Not to say that a passive journey in a normal cup isn’t a good thing – I enjoy that too. It’s just that it’s also fun to be able to control it and linger on interesting tastes.

Even before I found these glasses, I’ve always gone out of my way to drink coffee out of glass glasses. Call me crazy, but I just think coffee and espresso just taste better out of glass. It’s well accepted that coffee tastes better when you don’t put it in a to-go cup but drink it in a porcelain cup at the coffee shop. For me, it’s the same sort of analogy: I can’t exactly say why, but for me coffee in a glass just tastes better.

Finally, the hand-blown glass just looks and feels cool. Bodum did a really nice job with the Pavina glasses. It’s somewhat magical to see your coffee hovering above the “bottom” of the glass, and it’s always fun to watch the coffee brewing into the cup. The insulating walls make it very comfortable to grip the glasses without a handle, and the curve of the Pavina fits well in your hand.

Yes, they occasionally break: they’re glass. But, for me it’s worth it.