I am going to make a coffee lager. Batch size is 15 gallons but I only want to make the coffee one 5 gallons. My thoughts are to rack the finished beer onto the roughly cracked beans and leave in contact for the entire conditioning/lagering period of 4-6 weeks. After such time I will rack into a new keg.
Questions are, How long is too long to keep the beans in contact with the beer? Should I incorporate brewed coffee along with the beans? And finally, how much beans would I use for 5 gallons?
Sounds like an interesting beer. Wish I had any experience whatsoever with what you are trying to do. 
So, these are just guesses.
Terrible answers, I know. Good luck though!
My experience is that a few days is plenty.
I am planning to brew a Coffee Amber Ale in Dec. I plan to ‘dry bean’ at ~90% attenuation which should be about three days before xfer to keg (10% + D Rest). I like to dry hop during active fermentation so the CO2 produced flushes the O2. I’m planning to use the same technique for the coffee.
I would have guessed at least a few weeks. I was going to the beans lager with the finished beer. Glad I asked
Let me ask you Dwain, what is your batch size and how much bean to batch size ratio?
3-5 days has been plenty for me. About 5 oz coarsely cracked for 5 gal.
Thanks Denny!!
FWIW, I never crack the beans. I add them whole and leave them for 3-5 days tasting the beer during that time to get the coffee flavor I want. By not cracking the beans, you will get the coffee flavor from the beans and extract very little if any caffeine from the beans. I have been doing this for years with my coffee porter and the beer always comes out really good.
Good to know, Goose! I never gave it any thought about extracting caffeine but I will consider it an added bonus to get some extra caffeine in me!!
I didn’t notice any caffeine from cracking them
I brew 4 and 2 gal in the fermenter for 3.5 and 1.5 into the keg. In this 4 gal batch I am planning to hang .5 oz per gal so 2 oz total in a bag: 2/3 whole beans and 1/3 ground. Steeping the coffee 3 days at end of fermentation.
disclaimer: I’ve never done it this way. I usually add brewed coffee after fermentation direct to the keg. But this time I am planning to source some gourmet medium roast coffee at one of the local shops. Maybe Guatemalan or something.
In How to Brew pg 199-200, Palmer recommends “a cpl oz up to .5 lb per 5 gal batch” and he warns against green pepper or mashed green peas aroma that can come from coffee beers. He suggests drinking them fresh due to oil content of the coffee that can easily oxidize. He also recommends Radical Brewing and Experimental Homebrewing for some ideas on qty of spices.
In his Mocha Stout recipe he uses .5 lb course ground espresso along with cocoa and cinnamon in a 5 gal kegged batch.
Much appreciated! I actually just finished kegging some beer. There is always a few quarts left over to enjoy…tank beer, sort of? But anyway I am going to do a bench trial in 1 quart. I will figure out the ratio of beans to beer based on some of the replies.
Ok, I put 7gr. of whole Yirgacheffe beans into 1 liter of beer and will let sit for 3 days. That’s a start to see how much to dose a 5 gallon keg when its time.
I think Dwain and Denny are right on the money. I’ve done coffee porters and a Vienna coffee lager, and two days with 5 oz (about 1 oz per gallon) gives a great coffee flavor without overpowering the style or coming up short. I coarse grind the beans like a French press, and in my coffee porter, I’ll also add about 2 oz of whole beans to a 10-gallon batch. This will help with aroma and if i remember it can add a softer chocolaty note.
I’ve added this in the secondary and I have also split the beer and added it to my keg for the two days so I can get two versions of the beer.
Hope this helps! Cheers!
Just a small but possibly impactful suggestion: unless you’re looking for a massive coffee element to your lager, you don’t necessarily need to coarsely grind the beans. I add them to a muslin bag and throw them in secondary. Cold brew will have a different impact but with beans, leaving them whole is best. That way you don’t have to worry about little pieces floating around and getting into spaces where they don’t belong. As for soaking duration, three to four days is typically a good time for beans. But if you have a wine thief you can taste as you go. Hope this helps.
I’ve had success with a tincture-like method where I steep coarsely ground beans (maybe 6 oz?) in a gallon of the finished beer. Then I measure out dosages of this concentrated tincture in 2 oz. tasters to see what I like, then scale up the addition to the whole batch size. I suppose with 15 gallons of this beer you can always dilute in the glass or keg if your method comes out too strong.
Ok, beans on beer for 2-1/2 days. Tastes pretty good. Very good aroma. Good taste for the bean choice. Made the beer taste drier that it is. Somewhat happy with it at this point.