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ÜBER GRINDING


The Uberproject has been keen to play with grinders and grind profiles since its inception. I did postearlier on this topic in April 2009. At Caffe Culture in London in May while working on the Uber Bar, I met with Luca Caneve from Ditting, which is where the 805( aka Mahlkoning Tanzania) is built, with Georg Lauridsen from Mahlkönig and James from Square Mile. My idea was to get the grinder gurus and the coffee guru and the nerdy middleman (me) to facilitate a research session where we could start to learn more about the perfect grind profile and how to achieve it. But where to start?

Mojo Grind profiles and Coffee - Away we go!
Mojo Grind profiles and Coffee - Away we go!
     

We eventually decided to begin with French Press and put together a program where we would take the best off-the shelf burrs in the Tanzania/805, which had already been mechanically modified for Caffe Culture (the first Über Grinder).

We compared those profiles available and I was surprised to see the so-called ‘Turkish disc’ grind profile came out as the best available, as it yields the closest to a single peak particle distribution at the particle size where FP lives.

 

standard Ditting 805 turkish disc at FP 'coarseness'
standard Ditting 805 turkish disc at FP 'coarseness'
       

From here, I set a pretty rigid framework for the day, Essentially, we designed grind profiles using sieves to fix the profile. We then brewed, measured and cupped them, with details below.

BREWING

We used Bodum insulated French press, varying only the grind with these brewing constants:

Coffee                          - Colonia San Juan 8 Estrellas from Square Mile

Water                          - 140ppm (8 degrees German Hardness)

Coffee to water           - 60g/L

Temperature                - 93.5ºC

Contact Time              - 4 minutes (see below)

MEASURING

We used the Extract Mojo to chart each extraction. Therefore all brews were filtered through oxygen bleached filters (using a Chemex) immediately after plunging, to ensure accurate TDS readings.

8 Estrellas single peak 93.5C FP
8 Estrellas single peak 93.5C FP
       

 CUPPING

We had Joseph Smith, Marco’s Sales Manager and WBC judge with David Walsh (theotherblackstuff and coach to 4thin the world barista Colin Harmon) along with representatives of Mahlkönig and Ditting with myself. We didn’t use any scoring paraphernalia, rather fixed on comparing the balance of each cup and using comparative notes on which achieve the best result – i.e. the brew with no unwanted bitterness and all the sweetness and character the bean promised, without skimping on body (I believe a current trend exhibits a fear of the balanced cup, preferring the easy hit of thin sweetbombs of coffee).

 

Sieves were used to deliver these chosen grind profiles for test
Sieves were used to deliver these chosen grind profiles for test
       

CONSTANTS

Before we cupped any of the brews, we chose what we wanted to compare.

We ‘designed’ grind profiles using the sieves and compared them against the standard grind. We then ensured we were achieving as close to 19% extraction as possible by allowing ourselves to play with the contact time.

 

Ultimately, I wanted us to compare the same coffee with the same roast profile extracted to the same percentage where the grind was the only differing factor to change the taste.

The result – a ‘single peak’ profile between 600 and 710µm as per below, as subsequently profiled in Ditting.

 

 

Is this the perfect profile for French Press Brewing>
Is this the perfect profile for French Press Brewing>

THE PERFECT PROFILE?

We reran the tests with an Indonesian Aceh, again from Square Mile, to find the same result i.e. this profile delivered the most balanced cup.

     

We will now attempt to emulate this profile in a new burr cut specifically for the Über Grinder. We will see how close current grinding technology can come to minimising fines while controlling the peak desired.

I know there are a ridiculously wide number of variables outside of those we fixed which influence coffee extraction, but hey, you gotta start somewhere!

 


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