9 Numbers

This is now the third post in a series i’m writing about my hands-on research to develop a recipe for a coffee oatmeal stout. Here’s the first part, and the second part is here.

When i last reported on my adventures, i was preparing for an experiment to soak different amounts of coffee for different lengths of time — all at room temperature — in about 5 gallons of water to determine the ideal approach to adding the coffee to the beer. The results are in.

First, a big shout out is due to BA user jojox for suggesting that soaking coffee grounds in plain water would not be an accurate test to parallel the effects of soaking the grounds in fermented beer. I really had no idea the presence of alcohol in the solution would have an impact, and i was skeptical that a 6% ABV solution would make any difference. But it really made a huge difference. I have no way of measuring the precise extraction rate, but the liquid from the bucket of ~6% ABV water was at least 3 times darker than the liquid from the bucket of plain water, both of which soaked identical amounts of coffee for identical lengths of time (2.5 oz of coffee in 4 gallons for 24 hours). A third bucket also had 5 gallons of plain water and soaked an entire pound of coffee for just 6 hours, and it’s color was about midway between the other two.

Taste-wise, the 2.5 oz in plain water had almost no coffee flavor at all. It was incredibly weak. Unfortunately, the coffee flavor of the alcohol solution was extremely difficult to judge, as the grain alcohol gave the solution an incredibly harsh alcohol burn that predominated, even though it was highly diluted. Definitely more coffee flavor than the plain water version, as you’d expect based on the coloration.

The “1 pound in plain water for 6 hours” liquid had noticeably more coffee flavor than the 2.5 oz in plain water, but it was still awfully weak. What we really needed was a version of the 1 pound solution that had alcohol in it, but it would need to be from a liquor that isn’t as brutal and overwhelming as PGA.

Rather than continuing to spend money on liquor and going through more coffee for further experimentation, i devised a plan for the beer based on the results of the completed experiment. My intent is to add a full pound of coffee to my fermented beer at the beginning of the day on a Saturday. I will add it to a bucket with a spigot. I will then taste a small sample of the beer once every 2 hours throughout the day. At whatever point i think the coffee flavor has reached the perfect level, i’ll pull the coffee out. It was this experiment that has led me to conclude a full pound in 5 gallons for a relatively short period of time will produce the best coffee flavor. I predict 4 hours will be sufficient, but i’ll know for sure when i sample the beer…