Grinding Finer / CBrC 2017

This past Sunday I participated in the Canadian Brewers’ Cup in Calgary. There were some exceptional coffees being brewed, some fascinating brew methods, and a solid group of competitors. In the end I ended up placing third, which is incredibly exciting for me, especially as it was my first time competing.

Overall it was a great event. It was amazing to meet such passionate coffee professionals from around Canada.

I got to brew the Kieni from the Nyeri region in Kenya, roasted by The Coffee Collective in Copenhagen. I’m really proud of my routine and recipe, and especially proud to serve such a delicious and well-roasted coffee.

My presentation was about finding what makes specialty coffee special, but more specifically how to do this. My answer, as you may have guessed, was quality at origin, transparency in roasting, and evenness in brewing. But I approached brewing evenness in a slightly unconventional way, on top of the usual stuff.

I’d like to break this down a bit.

My routine was primarily inspired by recent analyses of coffee grinding from Matt Perger and Maxwell Colonna-Dashwood. They, with others, recently published a paper analyzing how the origin and temperature of a coffee bean affects the way it grinds. They learned some very interesting things in their research, primarily the effect of origin on grinding (negligible), but there were also implications about the effect of bean temperature on grind distribution and the amount of surface area created by fines. (Let’s define fines as being 0-80 microns in size, as per the paper and this separate post from Maxwell.)

In recent days there has been hype about freezing coffee beans (as there should be), which helps increase the evenness of a grind distribution. From the discussion I’ve seen on the Internet, it seems this has been the biggest practical takeaway from the paper. However, it seems as though the bit about the amount of surface area created by fines was eclipsed by freezing coffee beans. I think that these findings about surface area have big implications.

In short, after laser diffraction particle size analysis, they found that a large majority of the surface area in a grind distribution comes from fines. With their given grind setting on the EK43, fines made up approximately 70% of the total surface area.

Now, I imagine that this number would shift, depending on your grind setting and grinder, but it also makes a lot of sense that most grinders would produce a significant amount of surface area with fines. Actually, the fewer fines a grinder creates, the more of a problem it will be, so working with the EK43 results will be a near best-case approximation, as it has been proven to create lots of fines, and the principles we discuss will be even more important when applied to grinders that produce fewer fines and less even grind distributions.

Okay, so fines make up a lot of the surface area in a grind size distribution. What does this mean?

Well, if 70% of a grind distribution’s surface area is made of fines, then a huge portion of a coffee’s flavour comes from fines. Then another portion comes from the outsides of large grinds, then an even smaller portion comes from the insides of all of the grinds. The more large grinds we have, the less flavour we have access to. It makes a lot of sense, then, that the grinder known for producing the tastiest brews (i.e. the EK43) also produces a relatively high amount of fines, as well as its tight, unimodal grind distribution.

This drives home an important point: contrary to typical understanding, an overwhelming portion of the flavour in any brewed coffee comes from the finest grinds. As Perger states in his aforementioned analysis, “Fines are our friends!” He goes on to say:

“…it becomes increasingly obvious that fines aren’t the villain; otherwise every coffee ever made would be horribly over-extracted.”

Now, if 70% of the surface area in a grind distribution comes from fines, we’ve got 30% of the surface area made up of the outside of coarse grinds.

What about all the other solubles buried inside the large grinds? They make up 0% of the surface area, but contain some large percentage of the solubles. We have plenty of solubles hidden inside large grinds — potential surface area — not immediately accessible to water¹.

This means that we begin extracting the outsides of large grinds much sooner than the insides. The further inside the grind, the harder it is for water to extract, and the less even our extraction becomes. Every individual micro-extraction would become less even the larger a coffee grind becomes, as we hide more and more solubles, or potential surface area, deeper within the grind. Imagine how much more we hide in a grinder that produces even fewer fines and more large grinds than the EK43. More large grinds mean more hidden solubles, which means less even extraction.

Maybe it doesn’t seem like a lot on an individual scale, but when you think about the number of coarse grinds, and the amount of surface area that could be created by breaking them into the size of fines, it seems a little daunting. Or for a funnier contrast, imagine brewing 20g of unground beans vs. finely ground beans. The middle of the unground beans would be pretty dry and the resulting brew would certainly lack depth of flavour.

I am convinced that large grinds inherently cause unevenness, and conversely, grinding finer increases evenness.

And this is the idea I built my Brewers’ Cup routine on.

The way I applied this idea was pretty simple: grind finer. If you grind finer, you produce fewer large grinds, you decrease the size of the modal particle in your distribution, and you produce more fines.

However, when brewing finer grinds, there is another important thing to consider: over-extraction.

Perger sums this up perfectly:

“The upper limit of tasty extraction is decided by the most-extracted particle. This is always the smallest particle. So it’s up to you to make sure no portion of the grinds ever get over-extracted”

Now, fines don’t intrinsically cause over-extraction. But they do slow flow rate in drip brewing, and they do increase evenness. If grinding finer leads to over-extraction, then perhaps it’s actually brew time, or temperature² causing over-extraction to take place. Or perhaps the coffee was already being partially over-extracted, but increased evenness has amplified these flavours.

The best solution seemed to be shortening brew time without coarsening the grind. If the grind is fine and the brew time is too long, then we have a wonderfully even and obviously over-extracted brew. Flow rate control, then, is incredibly important. I had to figure out how to speed up my flow rate.

One thing we often overlook when thinking about drip brewing flow rate is flow rate from the kettle. It is common to “pulse” the brew. The more pulses we use, the longer a brew takes. The more time passes, the more we extract. If we shorten the time it takes us to pour water, then we shorten the time it takes to pass through the grinds. I shortened my pre-saturation by 15s and poured all my water by 45s, as opposed to a typical³ final pour at ~2+ minutes. This shaved ~2.5 minutes off of my brew time, which is the difference between a delicious 4-minute brew, and a flat 6.5-minute brew.

The other variable to play with was temperature. I knew that higher temperatures could speed up flow rate, so I decided to try 212F/100C instead of my typical 204F/95.6C. This shaved about a minute off of my brew time, and I actually ended up making my grind even finer to fix my brew time at 4 minutes.

Using hotter water and pouring quickly, I was able to grind significantly finer within my target brew time.

I also want to note that my brew water composition seemed to affect flow rate. My experience was that when bicarbonate outweighed magnesium (I didn’t use any calcium), my flow rate slowed drastically. I have not done any controlled experiments with this, so take this observation with a grain of salt, perhaps Epsom.

I also used stirring during the pre-saturation to wet all grinds as close together in time as I could. I find that with the Kalita and other drip brewers if you don’t do this, then a very large portion of grinds stay dry until the end of the pre-saturation, or even later, which is a huge blow to evenness. On top of this, I poured water along the sides of the filter (*gasp*) to knock high-and-drys down, stirred above the grinds and vertically tapped the Kalita to knock them into the brew, and then stirred the grinds and again above the grinds again followed by one more tap to create a flat bed and eliminate channeling. Yes, lots of agitation.

Grinding finer and stirring helped me to increase evenness, pouring quickly and hot water helped me gain control of my brew time, and within 4 minutes I had tasty extractions, as high as 22.33% with my Porlex. My recipe was 14g coffee to 210g water with a target beverage size of 172g in a 4 minute brew time. My water had 54ppm Mg to aid in extracting complex acidic compounds and 50ppm HCO3 to help with balance. My water temperature was 98C/208.4F because that was where my kettle’s temperature maxed out in Calgary, presumably due to the high elevation causing a lower boiling point than home. I actually ended up using my Porlex for the competition because in a fixed amount of time it was able to give me notably higher extraction yields compared to the other grinders I had access to, indicating evenness.

This is how I came to my recipe. I was very happy with how the Kieni tasted, and felt my brews were very transparent. The resulting cup was tasting incredibly complex and nuanced, and the finish was clean and lingering, which I usually take as an indication of a good recipe.

I really do believe that grinding finer (and freezing beans⁴) will lead to better filter coffee. We just have to figure out ways to accommodate this in our brewing. This was one of my first attempts to do so, and surely won’t be my last. I am already thinking about next year’s routine.

If only there were machines that would pump water through very finely ground coffee at high pressures with excellent temperature stability.

Thanks once again to the organizers and sponsors of the Canadian Brewers’ Cup, congratulations to Javaid and Ben on getting first and second place, and props to everyone who competed. It was really great to meet such creative coffee professionals from around the country. I am looking forward to the future of competitive coffee in Canada.

Thanks to The Coffee Collective for supplying me with such an incredible coffee.


¹Maybe the exact amount of potential surface area could be derived by comparing the size of the smallest grinds to that of a coarse grind. We could compare how much larger a coarse grind is than a fine to figure out how much of this coarse grind would be exposed in surface area if it were broken into grinds the same size as a fine. If we subtract actual surface area of the coarse grind, we would know how much potential surface area is being hidden inside the coarse grind. I might take a stab at the math myself, but if somebody out there beats me to it, or if I’m thinking about this all wrong, I’d love to hear about it.

²Or maybe flavours we associate with over-extraction are a problem created by undiagnosed roasting flaws — but let’s stay focused on brewing for now.

³Think of a typical 30s pre-saturation, followed by pouring 1/4 of the remaining brew water every 30s.

⁴Unfortunately, I did not end up freezing my coffee before grinding, simply due to the logistics involved, although it would have helped my take evenness to another level, and is something to consider for next year.


One thought on “Grinding Finer / CBrC 2017

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s