Low pressure on Black Eagle

The most exciting thing in coffee at the moment is lowering pump pressure. The very act is no big science. But the research conducted by several professionals makes it science-backed.

Mat North, Michael Cameron, Matt Perger have inspired baristas all over the world. Including me. I wanted to give it a try.

But I work on Victoria Arduino Black Eagle. The machine with difficult access to its inside. The interactive menu allows you to change the pressure of the steam wand, but not the pump. Manual provides you with instruction to make a cappuccino, but there's nothing about the pump.

An insight

Black Eagle is the perfect choice for playing with variables. Pump pressure, temperature or extraction yield can be changed so easily it's a shame not to do it.

Benefits

Tastier espresso, higher consistency and respect from fellow baristas. And that's it.

Dialling in is about finding balance. You can find balance in uneven extraction. To exemplify, hitting 20% extraction with 9 bar pressure. But you will hate your espresso after a few times.

I got a coffee described as very sweet, with notes of lemon, peach, jasmine and caramel finish. The problem is, for 3 months of working with this coffee I never went past lemon and jasmine. I was dealing with an astringent, harsh, bitter and overwhelming aftertaste, doing my best to get the lemony one. "Has some sweetness" meant balanced extraction. The body was watery.

Until the day I lowered the pressure to 7 bars. Lemony start, followed by jasmine and sweet mango with a syrupy finish. The mouthfeel is round and creamy. The new espresso cuts through milk much better too.

In terms of consistency, I waste much fewer shots. Channelling still occurs but it's pretty rare. Making workflow on busy morning smoother.

Lower pressure helps especially with a guest coffee ground in EK43. No matter how tasty shots you can pull on EK, the grinder is not designed for espresso during busy times.


Photo - Niall Kennedy

Ethiopia Duromina

Today I cupped away from home. Nothing new. But the first time I'm going to write about that cupping. Reason for that being I was alone.

Duromina is a relatively new thing. A cooperative of over 100 farmers to make better coffee. Jimma Zone has perfect climate for growing coffee, but it's always been low quality.

Now, as they've switched to washed processing due to Technoserve financing, their coffee is easily scoring over 90. Complex, clean and with a depth of flavours, it gets the best prices in Africa. The mill investment was repaid in only a year, instead of planned 4.

Details:

Origin: Ethiopia, Jimma Zone, Oromia
Varietal: Heirloom
Process: Washed, dried on African beds
Altitude: 1900-2000 masl
Roaster: Taylor Street Baristas
Score: 90.75

Cupping:


Fragrance: floral, lily, unusual for Ethiopia (maybe that how washed Ethiopia should smell)
Aroma: Very floral, with a distinct note of rose, not entirely uniform in terms of aroma

Flavour is like another level of Yirgacheffe. More delicate, no big flavours, but definitely big coffee. The depth and complexity got me lost. I have no reference for violet, but it seems to play a big role. Floral over fruity, but more interesting than jasmine and hibiscus.
However still fruity. Apricot, wild rose fruit, orange. Or maybe orange blossom. 65/35 for floral.

Acidity is beautiful. Generous but delicate. Not overpowering flavours and sweetness. Though again, not uniform from cup to cup.

Balanced like greatest Panamas, full-bodied like buttery Brazilians. Round, pleasant, silky, smooth. Yummy!

This coffee was scored at 90.75. I scored 90.5. It lost points mainly in aftertaste and uniformity. Probably some of these delicate flavours would linger a bit in the filter. But it shows the risk of flat espresso.
As far as I'm concerned cooperatives are not a great source of uniformity. Keep in mind over 100 farmers.

As for that, I cannot praise roaster enough. It would be a shame to hit another lemon/ginger/jasmine Geisha-like flavour profile as many roast Duromina that way. Frankly, I would use this coffee in the Brewers Cup.

Why 9?

Lower pump pressure means 3 interesting things. More gentle water flow - less chance for channelling. More even saturation of the grounds. And less fines migration.

Considering the arguments above, how on earth everybody got stuck on 9 bars for so long?

History

The first coffee machines made "espresso" more like filter coffee. Successively the pressure was higher and higher. Which allowed for about 30s extraction of concentrated beverage known as espresso.

It's clear, that taste wasn't the critical factor. So, let's say the goal was to extract more. Understandable, but extraction percentage in relation to pump pressure is Gauss's graph. Therefore, as you increase pressure, you get higher extraction, but only to some point. After that, increasing pressure lowers extraction.

The reason for that is uneven extraction. The peak point of the graph depends on coffee used, grinder, baskets, distribution, tamping and hundreds other factors. The thing is, usually the peak point is around 8 bar with perfect technique (the one you do competing).

Café environment

Pulling 100 shots per hour, for 10 h on shift is a different case. You have to be consistent. And consistency derives from minimising unpredictability. Pump pressure is one of them.

Let's assume you have a decent tamp - firm, level and consistent. But everyone makes little mistakes from time to time. The tamp no. 793 of the day might be of lower quality. Lighter and not perfectly level. 9 bars would cruelly channel it into 22s shot (everyone is weighing shots, right?). Not acceptable. But 6 bars would gently go through the puck extracting servable coffee. The shot would not be perfect, but you wouldn't tell the difference by watching the shot.

The example above shows how lowering the pump pressure minimises an obstacle in achieving even extraction. Mitigating negative factors is a key to consistency. It also allows you to focus on different factors. Such as temperature or distribution.

Extraction

The ultimate factor is taste. Always. Taste is correlated more to evenness of extraction that extraction. The question is, can you taste uneven extraction?
Tasting this is like a reawakening. Once you get used to 6-7 bar pressure, pull a shot on 9-10 bar. Even if the shot doesn't seem to be channelled it's gonna be hell in your mouth.

Some critics may say, that getting used to 6 bars worsens your technique. Just like getting used to gravimetrics or volumetrics deteriorate to stop your shots manually. There's a hint of truth in that. However, stopping your shots manually has never been the best option (unless you really weigh the shot) - click here. Same with lower pressure. Getting ZERO chanelled shots is worth the game. We've gone far from tamping as hard as possible a while ago. Consistency is a major factor. And actually, you CAN tamp too hard - click here.