Like pebbles in a creek: parallels between Coffee and Mashing

Welcome to ye,

On top of this dreadful hobby of mine, brewing, I’m also (perhaps predictably) something of a coffee person, which is to say that I happen to brew frufru (read: single origin, preferably east African) pour-over coffees virtually every morning. And in brewing these coffees, and thinking about the other methods, like espresso and the classic french press, and their minutiae, I’ve come to notice some interesting parallels between brewing coffee and mashing grain.

The Basics

Perhaps the existence of such parallels should come as no surprise - both processes involve passing water through milled or ground corns (read: small hard things, thanks Alton Brown for that lesson) in order to extract water-soluble compounds. In fact, let’s take a second to briefly summarize each process, before looking at the details.

Coffee Brewing involves grinding roasted coffee beans to a size befitting the method (so, roughly course sand to powder), adding hot water (shots fired) for a set amount of time, and then extracting the resulting liquid, continuously or basically all at once (like in immersion methods, like the French Press).

Mashing is similar, but there’s a key difference - you mill the grains with a similar goal of exposing a maximum of interior without hurting your drainage characteristics (husks here being desirable, whereas chaff in ground coffee is, to my understanding, basically useless, if not quite deleterious), but then you add water at specific temperatures to activate enzymes dormant in the malt, after which you drain your solution, often adding secondary water to improve efficiency.

Wow, what poetry! Who needs Wordsworth?

The Parallels

Okay sure, buddy, we get it - hot water, small things. Wow. Striking insight.

Pump the brakes there, pal. Obviously that’s obvious - what really strikes me is how little the lessons of brewing have migrated into the coffee brewing world. While not all lessons apply, it’s a bit like two different sets of primitive peoples inventing wheels independently (and spoiler alert: the brewers came first, although malt roasting technology was copy-and-pasted from the coffee world - but that’s another post). 

First of all, there’s a reportedly lively debate in the pourover world about whether or not to stir at various stages, particularly during the bloom (the first step, where you add the water to coffee and let it sit to drive off CO2, evening out and improving extraction and thus improving flavor), but that issue is textbook brewing - you always stir when you’re mashing in, with really rare exceptions (*cough* underletting and mash rakes and some other things too *cough*) to avoid dough balls (literally, balls of grain that are hydrated enough to stick, but aren’t exposed to the solvent, i.e. water), and thus you should probably always stir your bloom to ensure even wetting - I do.

Then there’s the efficiency question - the folks at the (now mildly disgraced) Barista Hustle once wrote a post that I won’t bother looking up, that made the straightforward case that immersion coffee as a “house coffee” was an iffy idea, since filter coffee is more efficient, but if the coffee world were populated by homebrewers (I shudder at the thought), that’d be a waste of 0s and 1s; obviously Brew in a Bag (BIAB) is less efficient than batch sparging, which is less efficient than fly- or continuous-sparging, essentially because the last bit of liquid left in the kettle for each progressively better method is closer to water and further from malt syrup (again, if that’s not obvious, take my word for it).

But does this arrow also point backwards? Are there insights from the coffee world that are somewhat unexplored in brewing?

The Turtle and the highly-caffeinated Hare

The big difference between the two, fairly obviously, is the role enzymes play in brewing, but the consequence is perhaps more subtle: brewing coffee is way faster as a direct result of this. And thus, coffee brewers deal with another element of chemical extraction than brewers do, namely time and extraction rate (two sides of the same coin, mind you). These become much more crucial variables in the production of a quality product in the coffee setting.

(Disclaimer: these naturally matter to the commercial brewer as well; sparging is largely limited by the rising pH and lowering sugar content of wort, and its efficiency is determined, all else constant, by the length in time of the sparge)

Where does this play out? In French Press brewing, it’s the steep time, which isn’t super sensitive, and in pour-overs, it’s basically the timing of water addition, which is more sensitive but not hair-trigger; and then there’s Espresso. Espresso is hyper-sensitive to changes in extraction time, a function (largely) of water pressure and grind size, to the point where 5 second or 5 gram swings from a target profile are pretty big. That’s a big part of the reason that great espresso is tough to brew at home, and that great espresso grinders are generally way more expensive than great pour-over grinders - the need for high precision.

Specifically, since there is no valve on coffee brewers most of the time, the only way to regulate flow rate/brew time is, you guessed it, grind size, making that part of the process arguably the most important part, and why brew methods like French Press are so bulletproof - when the quality of your coffee is independent of grind size, more or less, then you’re more likely to nail it even though you suck at brewing coffee (I hope that hurt your feelings - not one person I know who brews French Press has any idea what they’re brewing, and it infuriates me. GOOGLE IT and that’s two links btw). Oh, and why does grind size affect flow rate? My guess is a combination of the higher friction afforded by the higher surface area to volume ratio of finely ground coffee, with probably one or two more effects tossed in, like Stokes’ Law. Anyone else able to parse that? Just me? Okay.

And while stuck mashes do exist as a problem in brewing (where the flow rate plummets due to a compacted grain bed), the use of valves as flow regulators basically sidesteps this sensitivity to grind size.

Oh, so is there any usefulness in this for brewers? Of course not. I mean, for me, the first rule of coffee club is...buy the best coffee you can, and as freshly roasted as possible (with, say, a 3 day minimum - google that too! “CO2 fresh coffee three days,” I may not always be there to shower you with links). And that carries over to brewing too, naturally, but the obsession over grind size is fixed by, you know, a handful of rice hulls and a ball valve.

Conclusion

The optimization of passing a liquid solvent through a solute trapped in granules is bound to be a crackable nut if the industries that require the knowledge to do so have revenues in the billions, as the beer and coffee industries do; it just surprises me somewhat that the two biggest such industries don’t really, you know, talk. 

And if, after reading this, you have a hankering for a roasty beer, well, we’re about to can a sick Cherry Porter (Flynn the Crow), and there’s a barrel-aging beer that’ll probably slake your thirst as well coming relatively soon (February, I believe), so get pumped for the roasty goodness

Cheers,

Adrian “has a lot of pent up feelings about coffee” Febre