Bottling and Enjoying Oatmeal-Coffee Stout

After ten days in the fermenter, my Oatmeal Stout was ready to bottle. I made it to be intentionally light on alcohol but heavy on flavor. As such, my final gravity (sugar level or density) was quite high for a regular beer, 1.018. This calculated to a final alcohol by volume of just under 3 percent. No problem, I was shooting for a more sessionable beer, or beer than can be consumed in a session without falling off the chair.

I had planned to add one more breakfasty addition to the beer just before bottling- coffee. Yes, that's right, coffee and beer. Stout has more in common with coffee than most people think. Much of the flavor that we associate with coffee comes from the roasting rather than the bean itself. Stout is made with dark-roasted barley, cooked with dry heat until it reaches the desired level of caramelization. The same chemical reactions happen in both barley grains and coffee beans, so the two share many common flavor elements.

I saved a cup of coffee from our morning pot to add to the fermenter with the priming sugar before bottling. To ensure no coffee grounds got into the mix, I strained the coffee through a muslin sheet to catch and floating bitter grains. I made sure to heat the coffee back to boiling for just a few seconds to sanitize it before mixing it in with the priming sugar to make a steaming, shiny, sugary sludge. In it went to prepare for bottling.

Priming Sugar, Coffee, and Muslin Strainer

25 Liters from Greatness

Just as a further note, the coffee was added after fermentation to preserve as much coffee flavor as possible. The fermentation process is pretty rough on delicate flavor compounds, and the bubbling action actually scrubs flavor and aroma molecules out of suspension in the beer and into the air. That's why fermenting beer smells like malt and hops, that smell is literally flavor and aroma leaving your beer and drifting into the air. 

Adding coffee (or additional hops, or fruit, or other flavor additives) after fermentation preserves more of these precious compounds. If adding something sweet like fruit, be aware that the yeast will attack this additional sugar and begin fermenting again! Calculate carefully and check your procedure.

I cleaned out and sanitized 25 liters of bottling capacity, and bottling went as smoothly as my bottling days ever go. My cupboard under the sink was again full of fresh, delicious beer.

Finished Bottling

Update: After a week, the bottles were carbonated and ready to be chilled and enjoyed. We noticed right away that the coffee flavor wasn't going to hide in this beer. The bright coffee taste seemed to be amplified by the roasty flavors of the stout itself. It's not quite in the realm of too much, but when I make this again, I will certainly back off just a weensy-bit on the coffee. It is surprising how one cup of coffee diluted in 25 liters can be so strong. 

The oatmeal gives the stout a nice thick mouthfeel without a starchy oatmeal taste or the need for excessive malt and alcohol. Even with the strong taste of coffee, a nice beer to be enjoyed one after another.

Final Numbers

Brew No. 044

- Brown sugar yeast starter (Cooper's yeast 17613 15- 7g)

- 1 cup oatmeal extracted at 168F

- "Sparged" (rinsed the oats) with warm water

- Boiled 5 minutes

- Mixed 1.7kg Cooper's Stout, 1.5kg Light malt extract

- Topped off to 25L at 68F

- Bottling gravity 1.018

- 1 cup (350 mL) brewed, filtered coffee, 3/4 cup unrefined sugar for priming

Good beer, good night!