Okay, folks, time for The Truth Bat. I'm frankly tired of seeing these errors crop up.
People, there is no earthly reason to add malt to your separate cereal mash.* Holding the mix at an amylase-active temperature before boiling is just as pointless.
The whole point of boiling the adjunct grain in a second vessel is because the process of boiling liberates convertible starches from the protein matrix.
In other words, there is nothing to convert until quite a lot of boiling has taken place. If you add malt and hold the cereal mash at a conversion temperature, you're wasting time, effort and barley malt. Because there's nothing to convert. Yet.
Avoid the homebrewer's temptation to overcomplicate a process!
Boil your adjunct grains for an hour. Add the entire mix to the mash tun during dough-in.
Think of it like this: You don't eat these grains until after you boil them, because the enzymes in your intestines can't get anything worthwhile out of them until they're boiled. Malt enzymes are the same way: they can't get at the starches until you boil the grains. So, if you eat these grains, all you need to do is cook it like you would to eat it. That's it! Really! The same holds true for corn/maize, quinoa, spelt, amaranth, whatever - you need to boil it to liberate starches from the protein matrix, so the enzymes can attack the starches and convert them to sugars.
Perhaps we can stop the confusion by ceasing to call it a 'cereal mash'. After all, it's cooking, not mashing.
As for conversion power, brewers of Light American Lager use 6-row malt because it has slightly more diastatic power than 2-row. Not much; 160°L vs 140°L. Still, when you're trying to convert a mash that's 50%+ unmalted adjunct, you need every bit you can get. All that is to say that, unless you're approaching 50% adjunct, plain ol' two-row has plenty of power to convert your adjunct cereals and then some.
This message brought to you by The People Who Are Stunned At How Much Extra Work Other People Make For Themselves Through Erroneous Assumptions And Who See How Silly Notions Become 'Necessary' After The Notions Go Round The Internet A Few Times.
* A bit of husk matter in the cereal might help to keep it from becoming a sticky mass of glop, but why bother? You're going to be adding it to - and presumably mixing it well with - a whacking great tub full of husk matter! You don't have to lauter the adjunct alone. If you simply must worry about stickiness, add a fistful of rice hulls or something and carry on. RDWHAHB, fer Crissakes.
as spring approaches, I'm feeling the need for nice "american pilsner" (IE: a blonde ale with real flavor)
