Oatmeal Stout IBU's (Jamil Zainasheff's Recipe)

After listening to the Jamil Show on Oatmeal Stouts, I've decided to give Jamil's recipe a shot. I entered it into BeerSmith and noticed my IBU level is very low (28 IBU) compared to what it "should" be (36 IBU). Here is the recipe:

Batch Size: 6.00 gal
Boil Size: 8.71 gal
Boil Time: 90 min
Equipment: Brew Pot (7.5 gal) and Igloo Cooler (10 Gal)

Ingredients

Amount Item Type % or IBU
9 lbs 6.4 oz Pale Malt (2 Row) UK (3.0 SRM) Grain 72.87 %
1 lbs Oats, Flaked (2.0 SRM) Grain 7.75 %
12.0 oz Chocolate Malt (350.0 SRM) Grain 5.81 %
12.0 oz Victory Malt (28.0 SRM) Grain 5.81 %
8.0 oz Caramel/Crystal Malt - 80L (80.0 SRM) Grain 3.88 %
8.0 oz Roasted Barley (500.0 SRM) Grain 3.88 %
1.80 oz Goldings, East Kent [5.00 %] (60 min) Hops 28.1 IBU
1 Pkgs English Ale (White Labs #WLP002) Yeast-Ale

Beer Profile

Est Original Gravity: 1.055 SG
Est Final Gravity: 1.018 SG
Estimated Alcohol by Vol: 4.81 %
Actual Alcohol by Vol: 5.08 %
Bitterness: 28.1 IBU
Est Color: 35.3 SRM

I know Jamil uses ProMash and there's usually some variance, but the difference is huge and I can't figure out why. I don't want to over hop this beer because my BeerSmith measurements were way off. Any thoughts?

The differences wouldn't be that much. Are your hops the same AAU%? If not, you need to up the hops a little. Also, in an oatmeal stout, you probably won't notice a difference of 8 IBU's.

The AAU% are the same (5%) as Jamil's recipe. I'm sure the beer will be fine even at 28% IBU, but I'm just curious as to why my recipe is that far off.

There are several different algorithms for estimating IBUs. BeerSmith allows you to choose between the Rager, Tinseth, and Garetz methods. Try switching these under Tools --> Options --> Bitterness and you'll see how much they can vary. It is likely that the method BeerSmith is currently set to is different from the one Jamil used in his.

I also discovered this when crafting my oatmeal stout - depending on which formula I used, the IBUs varied between 27 and 46. This prompted a whole thread on the subject that might help you understand the dilemma - https://www.homebrewtalk.com/f39/beer-smith-overhopping-103930/. I now keep BeerSmith set to Rager since it seems to correspond best to my interpretation of bitterness.

Boil time in the book is 60 minutes also, you have 90 entered. that could make a difference.

I'll definitely check on what method my BeerSmith is set on.

As far as the boil time, it's at 90 minutes with a 60 minute hop addition based on the Jamil Show. I actually thought about bumping the hop addition up to 90 minutes with the start of the boil to increase the IBUs a little, but will probably keep it at 60.

EDIT: Rager method bumped the IBUs up to 33.6, so it looks like this was the main difference. Thanks for the advice.

Your batch size is 6 gallons.

Oddly enough that's the batch size he gives. I was going to scale it down to 5 gallons once I figured out the IBU situation, but I don't know why Jamil sometimes provides recipes for 6 gallons. I figured he'd either do it for a 5 or 10 gallon batch, but I guess it's not a big deal to just scale it back for 5.

I think he plans for 6 gallons so 5.5 make it into the fermenter and then there is 5 gallons after trub.

Yes, that is the reason. All of the information on formulas, volumes, etc is in the book around page 40 or so in the section, how to brew these recipes.

BeerPressure said:

I think he plans for 6 gallons so 5.5 make it into the fermenter and then there is 5 gallons after trub.

Click to expand...

so what volume do you use to estimate IBUs - volume of the boil, volume into the fermenter, or volume out of the fermenter (i.e. 6, 5.5, or 5 gal)?

Good to see you pop in again, Jamil. Don't be a stranger.

Thanks for the responses. I actually just ordered Brewing Classic Styles and Designing Great Beers so I'll be sure to check out page 40 once it arrives (and maybe I'll take a look at the other pages while I'm at it).

Shortly after I started brewing I had to take about a 9 month hiatus due to moving and starting a new job. Now that things have settled down and I've had a chance to get back into it, I found the Brewing Network and realized that there's so much that I don't know. I'm going back and reading The Joy of Homebrewing and How to Brew like I should have done in the first place, and hopefully the new literary additions will help round out my understanding of brewing and the different methods used for each style.

Thanks for the help on this one!

piperbrew said:

Thanks for the responses. I actually just ordered Brewing Classic Styles and Designing Great Beers so I'll be sure to check out page 40 once it arrives (and maybe I'll take a look at the other pages while I'm at it).

Shortly after I started brewing I had to take about a 9 month hiatus due to moving and starting a new job. Now that things have settled down and I've had a chance to get back into it, I found the Brewing Network and realized that there's so much that I don't know. I'm going back and reading The Joy of Homebrewing and How to Brew like I should have done in the first place, and hopefully the new literary additions will help round out my understanding of brewing and the different methods used for each style.

Thanks for the help on this one!

Click to expand...

Designing Great Beers is an excellent book. Lots of useless info about the history of beer styles, but great for putting together your recipes based on style.

When calculating IBUs you always use the amount at the end of the boil.

I'm pretty sure Jamil uses Promash and it defaults to Rager for calculating IBU.
I think Beersmith defaults to Tinseth so there is your difference.