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.