Mashing efficiency - Cracked corn, milled cracked corn, corn meal

[kmmuellr]

I was looking for some info the other day and couldn't find it, so I thought I'd share something to the forum instead of just asking questions! What is the difference in starting gravity using cornmeal vs cracked corn, and does milling the cracked corn make a difference?

Long story short:
Cracked corn - 15 brix (1.061sg)
Milled cracked corn - 16 brix (1.065sg)
Food grade Corn meal - 17 brix (1.070sg)

I've been homebrewing since 1996, and AG since '97 or so. I've never really been a numbers kind of brewer until I started distilling last year, so I could estimate what I should get out of the still. For Christmas I got a mill (Cereal Killer from Adventures in Homebrewing) and have been playing around with my gap trying to improve my efficiency in brewing. I've gone from 55-70% when the store milled my grain to 81-85% when I have the mill gapped at 0.029". I brew in a bag on an electric, PID controlled brewery where I recirculate the wort continuously. My mashes are 75-90 min.

My first bourbon and first cereal mash was in January and I used 60%/20%/20% corn/rye malt/barley malt, 2lb grain per gallon of water. I used cornmeal that I got from an Amish store in northern Michigan.
1. Bring 12 gal water to a boil in beer boil kettle.
2. Drain water to open keg fermenter, and mix in corn while adding water to break-up any clumps. Settled in at >185.
3. Wrap in blankets to insulate. Wait, stir, wait, stir, etc. All told I was confident the cornmeal was gelatinized after about 4 hours. I waited another hour (temp in the high 160's), cooled and added my rye and barley malts and rested at 148 for ~3hrs for conversion. No added enzymes.
4. Cool, pitch yeast and ferment on grain
5. Bucket ass press in brew bag to separate grain from beer.

Yesterday I repeated this w/ slightly longer rest times on two batches. One with with cracked corn, and one with cracked corn that I ran through my mill at around 0.032-ish (gap opened during crushing from 29 to 32 or 33.)

Cracked and milled showed an obvious difference in texture of the beer/wort after a few hours. The cracked NOT milled stayed pretty thin, where the milled appeared to start gelatinizing, but nothing like the cornmeal did. That turned to polenta in the kettle!

After an all day mash, I cooled and pitched at the gravities mentioned above.
Cornmeal at $0.50/lb
Cracked corn was $13 for a 50lb bag, so $0.26/lb. I'm sure I can get it cheaper up north at the co-op near my in-laws summer place.

Depending on how the separation of the beer goes in a week or so will determine if I continue to use cracked corn, mill it, or use cornmeal (assuming the taste is comparable). I'll also likely start doing an overnight corn cook vs starting in the morning and waiting all day. Corn meal was a bit of a pain in the ass. If the cracked corn separates significantly easier, I'll sacrifice the lower starting alcohol!

K