Slayer – Leveraging Pressure for Flavor Profiling

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Jun 06, 2009

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One nice thing about building Slayers in Seattle USA is that there is no shortage of great coffee roasters willing to try out a new thing.  In fact, not surprisingly it’s primarily the most artisanal roasters of extremeness that have taken notice.

Proximity like this also means that there is no shortage of great coffee to dial in for flavor profiling.  We have tried quite a few of the local greats.  Zoka’s Paladino, Vita dal Sol, Stumptown Hairbender, and Vivace Vita & Dolce.

Each of these coffees dials in differently from the others.  An “optimal result” depends entirely on the blend. So brew pressures vary depending on what’s in there.  So far everyone has stuck with their recommended brew temperature holding this number constant.

Getting Optimal Results

When I say “optimal results”, what I mean is this.  Each of these coffees has within its blend the compressed notes of flavor and fragrance that characterize that coffee’s constituents. These notes range from floral, berry scents and flavors to chocolatety ones.  This is a little analogous to differentiating flavor in general on a range from savory to sweet.

There is obviously a lot of subtly and variety in that band , and these could be described in millions of ways, depending on experience.  In a general culinary context, pure sugar could represent the far side of sweet while salt might define the extreme opposite edge of savory.  With coffee, one end seems to be floral sweetness, and the other end chocolate beyond spiciness, low-pitched flavor notes. The SCAA posts a flavor wheel that greatly elaborates on this concept.  But hopefully you get the idea I’m trying to convey here which is that there is a band of flavors in coffee and it stretches over a range from one extreme to the other.

So, “optimal results” in the case of the Slayer means opening up the coffee to highlight a desired set of flavors to get an intended profile. Slayer enables the user to pull these flavors out individually.  By adjusting pressure during brewing, it is possible to highlight any one flavor more than the others or play them equally. At a fixed brew pressure of 9 bars you don’t have this flexibility.

Purpose blending, Purpose Brewing

Most espressos are purpose blended for an overall flavor.  To brew these, roasters call out a brew temp, assume the machine is set to 9 bars of pump pressure, and suggest a time factor for extraction, usually around 25 seconds.  However, what roasters and baristas are finding is that even existing blends have totally new horizons of possibility that we didn’t know existed before, when pressure becomes variable.  It is fun to discover these.  It is not hard to imagine that someday blends could be created purposefully to utilize Slayer’s flavor amplification potential.  Delicate single origins also play well under these conditions too.

We have been identifying our brew parameters like this:

3.5 bars -16 seconds, 9 bars -7 seconds, 3.5 bars – 4 seconds, off.

2.5 bars – 10 seconds, 10 bars-18 seconds, off.

This format represents an initial brew pressure and time, a full pressure brew and time and a return pressure and time, which includes a tailing off of pressure.  The shots pulled on Slayer tend to be longer than the prescribed 18-23 second range.   We are finding results in the 30-35 second range.

The two profile samples noted here produce significantly different results from the same coffee.  Yet either espresso would be considered excellent, though one has a more chocolatey, full body, while the other has more flower essences, and a lemon finish.

One thing to remember is that regardless of how Slayer is used to brew, it adds no new flavors to the coffee.  All flavor is in the coffee to begin with.  Slayer can only amplify the characteristics that are inherently in the beans to begin with.

Now back to building machines.

Eric Perkunder

in Seattle