Brew Colloids and Fine French Press Flavor: Part 2 of 2

Brew Colloids and Fine French Press Flavor: Part 2 of 2

by Nate Jones
(Read Part 1 of 2)

Last week's tech-a-thon was all about how brew colloids, tiny masses of fine coffee and oils, trap flavor solids. The post concluded with the suggestion that the Coffee Catcher may allow active colloid management for the first time. First off, this article should be taken as an invitation to explore further - not the definitive truth on the Coffee Catcher's role in French press brewing. After six months of daily brewing, I've developed enough ideas to lay out some questions I'd like to discuss further, and this seems like a good time to invite the coffee community to weigh in.

One of the most consistent test results we've had with the Coffee Catcher has been apparent direct filtration of a significant % of brew colloids, with colloids separated from the brewing area and the cup by the stainless Coffee Catcher disc in the carafe. Coffees have tasted cleaner and flavor profiles have held up longer. At first, my assumption was that the key variables in this filtration process were the size of the mesh and the strength of the pressure wave generated by depressing the plunger in the French press. However, Sam Lewontin (@coffeeandbikes) pointed out that Scott Rao has argued that cleaner flavor comes not from a finer filter that traps more colloids but from the physical arrangement of the brewing system itself that either naturally separates heavier colloids or does not. 

Thinking in terms of brewing systems rather than mesh size, I now suspect that most of the filtration occurs in the first few seconds of the brew, as water is being poured over the bed of coffee on top of the Coffee Catcher. The turbulence and downward pressure generated by hot, falling water generates an initial mixture of coffee and water, and I think that that heavier colloids may naturally separate so that colloids are pushed beneath the disc by water pressure and turbulence during these first few seconds. Colloids would then be kept from brewing with the coffee from the start of the brew. In that situation, the cake of grounds atop the disc would effectively plug the press and keep filtered colloids from entering the cup when the press is emptied.

So here's the question: I've been able to achieve "full" filtration using the Coffee Catcher disc with a regular pour of hot water. I've also achieved apparent zero filtration multiple times by deliberately pouring very gently and slowly directly over the Coffee Catcher. So if no filtration and "full" filtration are possible, would it be possible to vary the pour pressure to achieve different levels of filtration? Think Hario pour overs, but for French press.

Another potential brewing system tweak introduced by the Coffee Catcher is a more effective French pull, a technique referenced in a thread over at Home-Barista.com. During a marathon brew session a few weeks ago, Alex Negranza (@Barista_Alex) and I experimented with bottom filtration of the press - pulling the Coffee Catcher immediately after the brew cycle was complete.* To our palates, the results were distinctive and intriguing, including a softer mouth feel and a seemingly rounder flavor profile with more fruit. In system terms, pulling the Coffee Catcher seems to filter very fine coffee solids in the foam and the brew, but doesn't seem to remove brew colloids filtered beneath the disc.

So here's the question: does the Coffee Catcher indeed produce a French pull with a distinct flavor profile relatively easily? If so, how and why is this making a difference relative to traditional French press techniques?

Finally, Alex has written an interesting post over here about siphon filtration using a modded Coffee Catcher. The common theme with the French pull above is vacuum, or bottom filtration of some sort. I'm all questions on this one. What exactly makes bottom filtration distinctive? Is it only that filtering from the bottom keeps fines at the top of the brew from coming through, as Rao has suggested? Is a relatively mild vacuum beneficial in flavor extraction terms? Can bottom filtration be tweaked (either by modifying pressure or mesh size) to extract a more desirable flavor profile? 

So, that's where I'm at. The Coffee Catcher will soon be in the public domain, and I hope sharper minds than mine will tackle some of these Q's - brewing up delicious coffee along the way!

* Please Note: this involves getting fingers close to hot coffee, and you could be burned. Try at your own risk! In practice, it seems the surface of the coffee cools extremely rapidly, and I've yet to burn myself touching the surface of the coffee during a pull - even immediately after brewing. Nevertheless, you should use your own judgment and proceed with caution as you try this.

French Press Throwdown Details

For those readers interested in competing in the Kaffeologie French Press Throwdown on June 18th (which coincides with the Coffee Catcher Launch Event), here are the competition details: *

1. Coffee: bring your own, but we will have some of our personal favorites if you forget yours.
2. Equipment: Grinders, timers, cups and water provided. Bring your own press and any technique-specific equipment. We will have extra presses if you forget yours.
3. Start: A little after 7 PM (party starts at 6).
4. Prizes: If it's ready, 1st prize receives the very first Kaffeologie French press! Otherwise, a set of Coffee Catchers (medium and large). Prizes will also include coffee and swag from sponsors. Second and third prizes will be awarded.
5. Time: 15 minutes to dial in, brew and serve your coffee. To keep things moving, you'll warm up as the person ahead of you is brewing and serving.
6. Structure: high score over the evening wins.
7. Cup Criteria: each factor to be assessed on a 1-5 scale, giving 20 points per judge, or 60 points overall.
      A. Clarity - a coffee's ability to hold multiple distinct flavors
      B. Roundness - the opposite of a sharp flavor
      C. Mouth feel - a coffee's feel in the mouth apart from flavor
      D. Audacity - points for bravery in technique or coffee choice
   

* Thanks to Throwdown Judge, Sam Lewontin (@coffeeandbikes) for helping lay out the competition criteria. The rest of the judging panel to be announced shortly.

Brew Colloids and Fine French Press Flavor : Part 1 of 2

Brew Colloids and Fine French Press Flavor : Part 1 of 2

by Nate Jones

(What a title!)

First off, hat tip to Sam Lewontin of Why Not? Coffee for the conversation that started this and to Scott Rao, who helped me understand the relationship between colloids and coffee body/flavor in Everything but Espresso and The Professional Barista's Handbook (TPBH).  (Head to home-barista.com for a handy quick reference quote from TPBH on brew elements. )

Jumping in, the non-water part of coffee is a mixture of dissolvable coffee solids and gases (the stuff that gives flavor and aroma, respectively) and non-dissolvable solids. These (relatively) large non-dissolvables form colloids as they spread evenly through water during brewing, bonding with tiny oil droplets and trapping dissolvable solids before they can dissolve. Another way to put it: suspended masses of particles, oil and dissolvable solids are known as brew colloids.

Brew colloids affect coffee in two key ways. First, these relatively large masses of coffee stuff contribute to the coffee's perceived weight in our mouths (body) and to mouth feel (a looser definition that encompasses body, but also texture, consistency and anything else your mouth feels apart from taste). More colloids in coffee = greater body, and of course traditionally brewed French press coffee is loaded with colloids and renowned for its heavy body. The down-side of all this body is a muddy, blurred flavor profile. In traditionally-brewed French press coffee, there are so many brew colloids that a significant percentage of available dissolved solids are mopped up before they can dissolve and lend their specially tasty chemicals to the brew. So instead of tasting the full orchestra of flavors, the tongue tastes available flavors plus colloids, which are perceived as both/either heavy body and syrupy mouth feel and/or a muddy, or silty mouth feel that screens flavor.

No surprise, one key to good French press coffee is balancing the number of colloids formed in the brew for an optimal body - taste experience. Previously, the only way to influence the number of colloids in the brew was to prevent them getting into the carafe in the first place - in other words, to employ a high quality grinder that produces grinds of a consistent size with a low percentage of relatively tiny colloid-forming coffee solids. I think there is now a second way to manage the body - taste balance: the Coffee Catcher.* I've conducted daily (tasty) brewing experiments for six months, and I think the Coffee Catcher can consistently remove colloid-forming solids from the grind mixture at the start of the pour, before many oily, flavor-trapping colloid masses can form. The result is a lighter-bodied French press brew, with significantly improved flavor clarity and extended coffee life-time. It may be that the latter occurs because there are fewer colloids in the cup, and therefore undesirable flavor extraction at cooler temps is minimized (solids that dissolve at cooler temps tend to release undesirable, bitter flavors into the cup).

But what's really tantalizing is the potential to actively manage colloid presence within the carafe for the first time. More testing is needed, but it's possible that certain brew conditions can be deliberately tweaked to influence the colloid transparency of the Coffee Catcher mesh - thus potentially allowing French press users to actively tweak the number of colloids in the brew, tailoring the body-taste balance to a particular coffee or brew parameter. I'll lay out my thoughts on this more fully in Part 2, due out next week...

*Legal Stuff: The Coffee Catcher is a patent pending product of Kaffeologie (TM), all rights reserved.