Cold-Brewed Coffee Stout

20 Nov 2016

I attended a talk by Dan Beis at the last National Homebrewers Conference on “cold mashing”. Today I had a chance to put it to work.

The idea with cold mashing is to “mash” some of the malt at a cold temperature (below room temperature). This extracts just about everything you could want from a grain, except the starch – and obviously, very little conversion occurs. Dan talked about using this technique to pack flavor into low-alcohol beers, among other weird techniques.

I set about making a coffee stout, and I had a bunch of high-roast malts to include. I put two pounds of those grains into cold water (at the rate of 3lb of water to 1lb of grain) and stuck it in the brew fridge overnight. In the morning, I “lautered” the grains using a kitchen strainer, pouring about half again as much warm tap water (so, 1.5lb per rlb of grain) over to help rinse the grains.

Steeping Jar

The grains smell and taste pretty interesting. They are not sweet, since most of the carbohydrates remain in long-chain form. They do extract some of the bitterness of highly-roasted grains – I wasn’t expecting that. But otherwise, I noted all of the normal flavors: chocolate, fig, coffee, and so on. All without any heat, and with very little sugar (Dan says to expect about 25% of the usual extract).

Steeped Grains

Dan suggests a few options for bundling the result into the beer. I chose a relatively simple option: use the result as part of the mash liquor. To do so, I heated the steeping liquid (which left most of the starch in the grain) to mashing temperature, then pitched it into the mash. The heated pot resembled a 2-gallon pot of espresso:

Steeping Liquor

From there, I brewed as usual: mash, sparge, boil, etc. To add additional coffee flavor, I ground enough coffee to make a pot, and drew off enough boiling wort to fill a french press. I let this sit for the standard four minutes, then pressed the strainer down and poured the result back into the kettle.

French Press

Of course, I tasted a bit, and it reminded me of nothing more than a redeye – the coffee’s acidity plus the bitterness of espresso.

The beer has just gone into the fermenter, so no word yet on how it will turn out. If it’s OK, I’ll have the recipe up on the site!