9 Numbers

Following up on this post, the tasting of hopped coffee-infused oatmeal stout is complete.

Five people participated. I am the only hardcore beer geek out of the group, the other four are all baristas. We tried three samples of oatmeal stout, each sample featuring a different hopped coffee. The hop/coffee combinations were 1) Kent Goldings and Ethiopian Harrar, 2) Saaz and Brazil Daterra Reserve, and 3) Willamette and Peru Norte.

The Kent/Ethiopian sample was very interesting. A bit tart and fruity, mainly from the coffee. While i liked it, we all agreed it was not the best choice. I believe a beer brewed with that would be “love it or hate it” without much middle ground. The Saaz/Brazil sample was pretty good, but there was something just a little off with it. I suspect that although the Saaz went well with that particular coffee, once you added the flavors from the beer’s roasted malts it just didn’t fit. I don’t know if there are any coffee oatmeal stouts hopped with Saaz, but i suspect not. It’s just not very well suited to the style. The Willamette/Peru sample was very nice. We found a winner. You got a little of the hops, a little of the coffee (very smooth), and a little of the stout. Nothing dominated; it all blended and complimented.

So that’s my final answer. My coffee oatmeal stout will feature late additions of Willamette hops and Primavera Peru Norte coffee. But one question is not yet laid to rest: how to add the coffee?

I was leaning towards the Spike Buckowski (of Terrapin fame) method discussed in this Brewing Network program. The coffee talk starts around the 1:36:00 mark. The gist of it is that he uses 1 pound of coffee per barrel of beer. Coffee coarsely ground in a mesh bag put in the secondary fermenter and left overnight — he cites a max of 48 hours. That would only be around 3 oz of coffee in a 5 gallon batch and for anyone who’s ever had Terrapin’s Wake ‘n Bake, you know that has a strong coffee flavor to it.

Naturally, i discussed the nuts and bolts of how to add the coffee with Brett, since he knows way more about the science of brewing coffee than i do. His first reaction was to recoil at the suggestion that it would be ok to leave the coffee in contact with the beer for as long as 48 hours. (Since Spike says he only leaves it overnight, i’m not sure why he extended that and said “not more than 48 hours”.) Brett told me something i didn’t know — you only want to extract about 20% of what’s in the coffee beans. Anything beyond that primarily leeches out harshly bitter, acrid, generally unpleasant stuff. Thus his philosophy is use more coffee over shorter periods of time when brewing; it’s better to get 20% of the flavor from a lot of coffee than 40% of the flavor from a little coffee. Very useful info.

Next we discussed amounts. He was very surprised at the proposal of 3 oz in a 5 gallon batch. He was skeptical that would bring out much coffee flavor in a stout. So he made a kind offer: if i bring him a couple 5 gallon buckets, he’ll fill them with water and let 3 oz of coffee soak in one for 24 hours and let a pound of coffee soak in another for 6 hours. There’s that whole “more coffee over less time” philosophy getting tested. That would be about 6 pounds per barrel of beer if scaled up!

So we’ll start the 24 hour soak tomorrow evening and start the 6 hour soak late Saturday morning, then do a tasting of both Saturday evening. I can then use the results of that to guide me on how much coffee to add to my beer’s secondary fermentation and how long to let it soak. Exciting stuff.

Update: BeerAdvocate user jojox has suggested that the presence of alcohol affects the extraction of flavor from coffee beans, and thus our proposed experiment with plain water will not be an accurate test. I don’t really know anything about the science behind his assertion, but it’s worth trying to control for this. So Brett and i have agreed to include a third bucket of water in our test, one dosed with grain alcohol to create 6% ABV water (i am planning on the final stout being 6% ABV). We can add 3 oz of coffee to that bucket and soak it for 24 hours as well. That will allow us to see what effect that concentration of alcohol has on the extraction of coffee flavor.