I love my job. And I don't mean I love being critical. I love my job here on CoffeeGeek because I get to play around with some of the most technically advanced espresso and coffee machines on the planet, and I get to taste some absolutely brilliant coffee and espresso.
During my visit to British Columbia's Espresso Coffee Machines Co. (ECM) to test out the World Barista Championship (WBC) official espresso machine for 2009-2011, I got to do both. The Nuova Simonelli Aurelia WBC Spec machine was finally in Canada - this is literally the first one in country - and I got to spend an afternoon learning all about the machine, pulling shots on it, and testing it on the tech side.
Danny Bresciani, son of ECM co-founder Remo Bresciani was my host, and we had a great time pulling shots and putting the machine through its paces. In part one of this article, I detailed some of the technology, benefits and possible pitfalls of the machine; in this part we get into a more detailed examination of heat exchangers, some temperature testing, and what's probably most important for me - the "so how does it taste!!!" nuts and bolts.
Temperatures and Shot Tastes
All the tech talk was over - it was time to get hands on with the Aurelia. I decided to brew first, and measure temperatures later. Bresciani had a utility coffee on hand and I had also brought some of Sammy Piccolo's 2009 WBC competition blend along to see how it would fare in the machine. Piccolo pulled me shots of his coffee (on a WBC-certified, not spec'ed Aurelia) over the past few weeks, so I had in my tastebuds' memory a baseline to shoot for.
I asked Bresciani to pull me a shot with the coffee they already had in the paired grinder and without any changes (ie, just what they had as 'stock') because I had a clear idea to test how an unknown (to me) coffee could be tuned up or down by my meagre barista skills. I got my baseline shot from Bresciani, tasted a bit of roast profile (it was a fairly dark roast), some temperature bitters, and some thinness. Then it was time to go to work.
What little I know about espresso is this - if you taste bitters, one possible culprit is too-high temperatures. If you're tasting excessive roast profile (carbon, caramel), ditto, but also dose needs to be looked at. Was this Aurelia capable of overcoming some slight deficiencies in the coffee? I changed dose (down), grind (finer), asked Bresciani to dial down the pressurestat by .05 (from 1.2 to 1.15). We had to perform a big purge and flush - the HX needed to get down to the newly set pressure - but once we did that, we started pulling tuned shots of espresso.
Good news? With only three attempts, we were able to make that espresso gain a solid scoring point - maybe 1.5 points - with really mild changes to grind, dose, and machine temperatures. Even better news - every shot after the re-dial in was consistent. I pulled about 5 doubles in a row, tasting each one, and the taste baseline remained the same. I had no idea what the grouphead temperature was, but at least I had a good tasting shot, and a repeatable shot.
The bad news? Well not really bad, but it did take some time to get down to the new temperature and have it "stable". It required a substantial purge on all three groups, and running the steam wands full open for about 10-15 seconds before Bresciani was happy with the new state. On dual boiler machines, this is much less of an issue - change the PID down on a LM or Synesso and you can be at the new temperatures with maybe a 5-10 second grouphead purge, no steam purging required.
WBC calbre espresso on the Aurelia
With this first test out of the way, it was on to Sammy Piccolo's competition blend for this year's WBC. Before we switched coffees, I asked Bresciani to bring the boiler pressure back up to 1.2 bar, and we futzed around for a while, so I didn't notice a bigger negative about the machine until later in the day (I'll get to it, promise). Bottom line we had a machine running full bore at the 1.2bar pressure by the time I got around to dialing in Piccolo's blend - there was maybe a 15 minute delay between pulling the utility shots, changing the pressure, and starting to dial in the new coffee.
The first shots showed serious need for grinder adjustments which we did. But by the fourth pull, I was getting about 80% of the quality and taste I was getting from Piccolo's own-pulled shots the week before. Big grapefruit, finish of caramel, nice medium acidity, good body. The shots looked gorgeous. And most importantly, once dialed in they were consistent. At one point Bresciani and I were both pulling shots and while it was obvious that different tamping, packing, prep resulted in different tasting shots (even different volumes!) between him and I, my tastebuds said that every shot Bresciani pulled tasted almost identical, and every shot I pulled had similar consistencies.
This was great news. One of the holy grails for espresso machines is consistency. Up until just a few short years ago, this was not really achievable by most baristas except for perhaps the most seasoned professionals. I am not anywhere near the capability or skill that a Piccolo or a Hoffman has (or for that matter the average barista at 49th Parallel cafe, or Intelligentsia), but I was able to be very consistent on a machine I had minimal experience on prior to this testing day. That in itself was a really good endorsement. My mind was reeling thinking about reasons why. I thought maybe the massive grouphead and the soft infusion system (as Nuova Simonelli calls the interior grouphead chamber) had a lot to do with it. Then I thought well, maybe temperatures are doing a major thing here.
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| Danny Setting Them Up |
Danny Bresciani setting up a double shot pull of Sammy Piccolo's 2009 WBC Competition blend on the Aurelia
| Great extraction |
In the first 10 seconds of extraction, after the soft preinfusion was done, the flow was just nice and tight.
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| 12 seconds in |
Shot at high speed, a nice extraction is caught in freeze frame, showing the gloopy high quality of the espresso pull.
| Finished puck |
We used a prototype CoffeeGeek tamper during this test, which Bresciani said improved already low instances of fractures and side channeling that the soft preinfusion usually takes care of.
Bresciani and I were both pretty much coffeed out by late in the day, so it was time to bring the Scace Device (a precise temperature measurement tool for espresso machines) into play and measure grouphead temperatures. This is where more surprises came into light, including ones that simply didn't make sense based on the drinks I was enjoying.
My first test was on the far left group (and the one furthest away from the HX's heating element). At 1.2bar boiler pressure, this group was running consistently at 201.2F (up or down .2F) for the first 20 seconds or so, then I noticed it start to slowly climb up. Running it for approximately 45 seconds showed a definite slight creep upwards, going up to a maximum of 202.4F by the time I disengaged the Scace off (indicated in the photos).
I put the Scace on the group on the far right (closest to the HX heating element) and ran the test again. 201.4F; very acceptable! But this one too started creeping up, and slightly faster than the far left group. I wish I could have run this test several more times to get more accurate results.
This test showed something good, and something not so good. Good was that the far left and far right groups had very similar temperatures - 0.2F is negligible - and after a fast rampup, held those temperatures more or less stable for the majority of the shot pull. The not so good was the temperature climb. I don't know much about espresso science but I do know that experts in the field have presented very clear cases showing that excessively high temperatures, especially toward the end of a shot are not good - they can bring out excessive bitters.
This is where I got very confused. The shots I tasted didn't seem to really exhibit this bitterness effect, except for the very first shots Bresciani gave me from the utility coffee. I watched the streams carefully from start to finish, and saw only minimal visual indicators of excessive blonding, or excessive overextraction which is endemic in prohibitively high brewing temperatures. Quite confusing. But then again, perhaps that's one factor in why I couldn't seem to get up closer to the quality of shots that Piccolo had made for me the week before with a nearly identical blend.
Nuova Simonelli and 2F temperature acceptance
In reading Nuova Simonelli's white paper on the Aurelia, one thing really stood out for me and that was their discussion on temperature stability. Their obvious bullseye target is dual boiler technology (they spend some of their text time in the white paper trashing dual boilers, saying they are "less reliable and more expensive to maintain..." as an example); on one of the first few pages they write "the temperature of the brew water of the Aurelia is stable to 0.5 to 1.0 degree Celsius (that's up to 2F at brewing temps) so there is no logical reason to add more boilers."
Well this was even more confusing! How did my initial Scace temperature tests show a stability down to 0.4F total range (or 0.2F, 0.1C up or down), when NS is proudly proclaiming 2F ranges? And what is Nuova Simonelli thinking if they believe a 2F stability range is acceptable in this day and age of machines providing 0.5F stability or even finer?
I think it comes down to maybe two things - when they first built the non PID Aurelia, 2F is what they got and what they felt was good enough. Now, with the PID controlled machine update giving 0.5F ranges, they either haven't updated the white paper, or are playing it safe with the numbers and we got a very tightly engineered machine to test on. I think the latter is the case, since I don't think the PID itself, controlling water in a 17 litre boiler, can make those kind of instant changes.
Moving on to the next test, I asked Bresciani to lower the machine pressure by .1bar (or two steps) to see what that translated to in temperature at grouphead. 1.2bar was giving 201.2F; what would 1.1bar deliver. It took some time to figure out - big grouphead purges, big steam wand purge, and then I did find out - it's roughly 4F drop - I was reading 197F on both the far left and far right groups. So this machine is adjustable (at least via the control panel) in 2F increments, give or take. It might be more finely adjusted with the flow restrictor tricks that Bresciani described to me (but I didn't see a demonstration of) for achieving different brew temperatures in each group.
My last test was asking Bresciani to put the machine back up to 1.2bar and to see if the machine would be back at 201.2F at the far left and right groupheads. Here's where the HX technology seems to really break down. It took over 10 minutes to achieve this change - here's what happened.
We changed the pressurestat PID setting to 1.2bar then ran a fair amount of water through the groups (which was a mistake - taxed the HX even more by doing that). I put the Scace on, and it was reading 197F (the same temps at 1.1bar!). Bresciani suggested we let the machine rest and get up to temp. I did so, trying again in about 3 minutes; still under 199F. More wait. Test again, and around 199.1F; I was flummoxed. About 10 minutes after changing the pressurestat PID controller, I was finally getting 201F range temperatures again on the grouphead.
| At 1.2bar |
Temperatures held steady going back and forth between the far left and far right group; but you can see in the "max" reading (smaller reading below main temp) it had climbed to 202.4 during the previous test.
| at 1.1bar |
This s a 4F drop for .1 bar difference on the pressurestat. Since you can adjust by .05bar and no finer, the temperature adjustments one can make just via the panel are approximately 2F up or down minimum. There may be other ways to more finely tune the temperature.
| Getting back up to 1.2bar |
This is about 5 minutes into trying to get the machine back to 1.2bar, 201.2 temperatures, from the 1.1bar, 197F temperatures. It took us about 10 minutes, but to be fair, I did purge some water through the heat exchanger thinking it might get things "flowing". and back up to temperature; a holdover from my LM days.
This is not so good. I obviously prolonged things by doing a flush on one of the groups for at least 10 seconds or longer (as an aside, there's an impromptu test of recovery, discussed later in this article). Even with that operator-induced hindrance, the fact is this machine takes a long time to get up to higher temperatures if your coffee necessitates that kind of change.
To me, this is one of those clear areas where a dual boiler setup champs out on a HX machine. A PID'ed dual boiler machine takes some time to get up 1F, 2F in temperatures, but not 10 minutes or more - they usually take only a minute or two max, even with 3 litre brew water boilers (dual boiler machines usually have massive steam boilers but relatively small brewing boilers). A HX machine like the Aurelia with a 17 litre boiler needs a lot more time, especially since we're dealing with pressurized water in temperatures far above boiling. Looking back, I shouldn't have been surprised by the time it took.
Was this a game breaker? Honestly I don't know. How often will baristas need to make their brew water 4F hotter? Is having to wait even 3 or 4 minutes for a rising temperature adjustment acceptable? With HX technology, there are going to be serious drawbacks that those using PID controlled dual boiler setups don't have to worry about. There's another common flaw with HX machines that I didn't get a chance to test on the Aurelia, and I wish I had because it'd be interesting to see how Nuova Simonelli tackled a very common HX problem: recovery time.
Recovery time is the achiles heel of a HX system in high volume cafes. Heat exchanging tubes or systems draw heat energy from the main volume of water in the steam boiler - that, after all is how water that enters at room temperature gets flash heated up to brew temperatures as it passes through the relatively small tubes. The more you do this, the more temperatures in the main water fall. In a high volume cafe, pulling a double every 45 seconds and steaming large volumes of milk is going to tax the heat energy and recovery time for HX boiler systems. Pulling one or two doubles every three or four minutes like we were doing won't show this problem, but, I've yet to meet a commercial HX machine that doesn't need some severe resting times after pulling 4, 6 8 shots in a row + steaming.
An amazing barista, one that has my deepest respect as a skilled technician, chatted with me about heat exchangers and brought up some similar thoughts. He presented a scenario - what if you've just gotten an order to make four large lattes, and you plow through these as quick as you can. The heating element inside any 17litre boiler machine is going to struggle producing all that steam, and all those quad shots. Then in walks one of your most serious, critical customers, ordering an espresso. Is that large grouphead counteracting the problem enough? Is the heat exchanger able to deliver the dialed in 200F shots at that moment? Or are you going to be forced to go with quality, and tell that demanding customer, sorry, we'll have to wait a bit.
So again, is this all a game breaker? Truth be told, I wasn't able to test for recovery, and I should have. We plowed through a lot of shots, Bresciani and I, and the machine seemed to keep up. But we didn't throw a Caffe Artigiano Hornby location 8:30am out the door lineup of shots at the test machine. At the end of the day, I can only truly evaluate and disseminate what I tested, and I kept going back to several things about the Nuova Simonelli WBC-Spec Aurelia that were just top of class, and taste was the most important factor.
So How Does it Taste?
There are three things I learned about the Aurelia that were exceedingly positive and game winners. First was taste. Shot quality was seriously good. With very little familiarity on blend, grinder and machine I was able to get 4, 4.5 point (out of 6) espresso shots; I'm pretty judgmental and harsh on taste tests, so this is a very high score for Piccolo's blend on the Aurelia.
Second was consistency. I marvelled at how, shot after shot after shot I pulled, the taste was almost identical. Part of that is thanks to the use of Nuova Simonelli's new digital doserless timer grinder which did a fantastic job of repeatable doses, but a lot had to do with the machine and its temperature stability on low-volume use. I don't know if banging out double after double after double for three minutes would have resulted in something different.
Consistency showed itself in two forms. At one point both Bresciani and were pulling shots at the same time. Bresciani's shots had a distinctly different 'tone' than my own just enough that I could identify different nuances. But while his prep style made for a slightly different tasting shot, I also noticed that every shot he pulled was consistent as well. That again speaks to the machine's ability to produce extremely consistent results.
Third thing I really enjoyed about the machine was usability. Steaming was nice. Ergonomics were fantastic. Controls were easy to use. I really liked the 'visibility' of the machine - shots weren't hidden, there's no massive overhang of solid metal hiding the tray. The lighting package makes visual inspection of the shots a breeze. I liked the soft feel of the control buttons, and assume they are silicone. Even the hot water dispensing (a mix system that can be dialed to different temperatures) was a well designed system. Nuova Simonelli won a usability award for this machine and it's easy to see why.
| Leather wrapped portafilter |
Seen at the WBC and here in white (waiting for barista's grimy hands to give it a patina), the portafilters just feel... perfect.
All that said, the Aurelia is not without flaws. In this day and age of temperature minutia in espresso technology, not having accurate readouts of grouphead temperatures on the front LCD panel puts it behind other machines in this class. I almost imagine this could be fixed by sticking a K-probe right inside of that preinfusion chamber in the 8kg grouphead, feeding internally to a temperature reading brainbox.
I spent some of this evening reading a 21 page white paper that Nuova Simonelli wrote on the Aurelia. It's obvious that a massive amount of science, research and engineering went into the design of this machine. It's also obvious that in some areas, they are playing safe with their numbers - claiming a 2F stability when I tested a .4F stability - what this says to me is that this machine is extremely well tuned. It's pretty safe to say Nuova Simonelli is probably the industry leader in terms of heat exchanger and grouphead engineering in espresso machines.
The thing is, it also seems as if Nuova Simonelli has reached the pinnacle, the absolute maximum performance that the heat exchanger design is capable of - a technology invented in 1961 for espresso machines. Compared to where technology in espresso is going today - individual group-cap boilers for each group (Dalla Corte), dual boiler, dual PID, heat exchanger pre-heating the brew boiler water (La Marzocco, others) and mix-valve fine tuning individual on the fly grouphead temperature controls (Synesso) - the heat exchange boiler/brew system is possibly at the limit of its capabilities and risks being left behind by these newer technologies. I saw the deficiency in changing temperatures upward, and believe there is possibly a recovery problem in high volume use, only because its a problem with pretty much every HX-based espresso system.
Don't even get me started on where I think the next holy grail for espresso is - temperature profiling.
The Nuova Simonelli Aurelia, WBC-spec or WBC-certified for that matter, is a brilliant piece of engineering technology and in many ways, a usable art form. Both classes are capable of producing absolutely stellar espresso shots. Both are capable of consistent, repeatable results. I tasted some amazing shots during my visit, and some world-beating shots produced on a WBC-certified machine when I judged Sammy Piccolo during his practise run for the 2009 WBC.
What will be really interesting is when we see what Nuova Simonelli has next up their sleeve. If they've learned this much about heat exchanger technology, I can't wait to see what they do with brand new paradigm technologies in espresso equipment and take a real stab at pressure profiling and temperature profiling as the next decade begins.