Oatmeal stout: Steeping or mash?

Question

Ladies and Gentlemen of Homebrewing, I was cruising my Google+ account, and I am stalking (I mean following/stalking) Wil Wheaton, and I noticed he is a homebrewer! Tonight he posted a question. I directed him here, however I doubt that he would read my post, so perhaps you all could head over to Wil Wheaton's Google+ Profile and help him out.

He asks:

I'm making an oatmeal stout for Jaime Paglia, and I'm trying to figure out the best time to put in the oats. This will be a partial mash, using extract for the base and some steeped specialty grains.

I can't find consensus on the usual forums. Some brewers say to put the oats (about 1 pound for a 5 gallon batch) in with the steeping grains. Others say you have to mash the grains with some 2 row, but don't say how much 2 row you should use, and how to scale back the extract if you go that way. I'm not afraid to do that kind of mashing (yay! experience!), but it's easier to use extract, so that's my preference at this point in my evolution as a brewer.

So I was thinking that I'd use the basic stout recipe I have, and I'd toast a pound of quick oats in the oven first, then steep them with the specialty grains when they were all toasty and golden and good.

I'm very interested to hear opinions on this, and I thank you all in advance for sharing whatever experience you've had.

You may also want to check out some of his other homebrew related posts.

Answer 1

You may notice your malt extract say something like "non-diastatic, unhopped, pure malt extract", or something similar. Diastatic power is the ability of a malt to convert starch to sugar. In an extract, you don't need it because it's already been converted for you. However, to get starch to turn into fermentable sugar, a diastatic malt is required. The typical malt with the high diastatic power is 2-row.

Adjuncts (such as oat), on the other hand, do not have this power on their own. That said, they can piggy-back off of the enzymes in a diastatic malt such as two-row to perform the conversion and get fermentables. This is why you may have heard that you need to use 2-row along with the oats. A 1:1 ratio should suffice.

Answer 2

If you don't mash the oats, you're simply adding starch to your wort. That starch can serve as food for bacteria and encourage an infection in your beer. Bottom line...don't steep oats. Mash them with a diastatic malt.

Answer 3

I made an oatmeal porter which came out really, really nicely. The mouthfeel was smooth and silky but not overdone. The only downside was that it had next to zero head retention.

To get the "smooth" palate, you need to mash the oatmeal with your grains, but you really do not want to overdo the oats. I used 100g oats in a 15l batch (about 1/3 pound of oats in 5 gallons) which was easily enough.

I plan on repeating my recipe but need to work out how to retain that head.

Good luck on the stout.