I assume that you mean breakfast cereal? I don't know what cereal you might have in mind, so I can't guess what flavor you're looking for to be able to give you a yuck or yay. I don't see any harm in experimenting, but sugary cereals will cause additional fermentation that you'll need to be concerned about. Maybe someone else in this forum has tried it and can give advice on how much to use if you want to identify your cereal choice.
I personally have never added breakfast cereal to a secondary (I would never even conceive of this). My worry is that you will be adding starches to the beer that the yeast cannot metabolize but other unwanted microorganisms (that are present in every homebrewed beer) will be able to metabolize these starches (which can result in off-flavors). Cheers!
I recommend adding 4 cups cocoa puffs, 2 cup whole milk and 2 whole banana sliced per 5 gallons. This makes for a complex, multi-dimensional beer.
As JackHorzempa said, you'd be increasing the risk of infection. I could see putting it in the mash though.
I was looking for a peanut butter flavor and considering peanut butter capt n crunch. I've seen the powdered PB2 used before and turned out great. I was just trying to try something different. I considered using it in the mash but figured I'd boil off some of the flavor in the process.
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Put it in the mash. There have been competitions where the special ingredient is cereal. Captain Crunch Stout is one I remember.
I don't recommend it at all, but if you are determined to try it, do it in a small batch. Maybe do a 6 gallon batch of stout or whatever and keg 5 gallons of it, and put the remained in small jug. If you bottle, expect gushers at the minimum, and bottle bombs at the worst.
Under no circumstances should you add cereal to your secondary. If you feel like dry-pancaking your batch though, that's a whole other story...
I get a lot of weird looks when I ask peoples` mothers that question. How much Bisquick should I add to secondary, and for how long? I see this needing another thread.
How the hell did WB/Evil Twin do that imperial donut stout? Didn't they actually mash in glazed donuts? Why didn't the grease mess it all up?
Ballast Point adds Captain Crunch to the finished product to make Victory at Cereal which smells exactly like Captain Crunch. Add until it smells right (~4 days) then rack off. Source: Brewer at Ballast Point who I emailed.
Based on the murky color and the goopy sludge found in Kuhnhenn's Cocoa Puffs stout, I would imagine they are using the cereal in secondary. I have no idea what proportions though. I've thought about racking a gallon of stout on to some just to see what happens.
