We made a batch of bourbon with corn that wasn't ground very fine. we didn't get a very good starting gravity. how much can a finer grind affect the S.G.?
Corn doesn't release its starches very readily. you can over come this a couple of ways, finer grind is one way, the other is a longer cooking time.
but do keep in mind corn doesn't have as much starch to be converted to sugars as other grains. but the flavor is much better in my opinion and very much worth the extra effort.
Mechanical grinding is the only way you'll get a full yield. Simply boiling longer won't break down those cell walls. Even with malted barley the difference between fine grind and course grind is usually a couple of percentage points in extract, even with a decoction mash. With corn you need to rupture those cell walls mechanically.
Seems like you already know the answer to your question.....
When I grind my corn it comes out just slightly larger than corn meal. I am using a plate grinder. 250# in 20 min. Coop
I have never used corn, is it always fermented grain-in or is it lautered?
With lautering the grain bed becomes clogged if ground too fine.
I assume you usually don't lauter so what is the problem with grinding it extremely fine
I distill with the grain off, just liquid into the still. I let my fermentation tanks set an extra day after head drops and grains settle to the bottom. Coop
Am I right in assuming that if you did a very fine grind it would take too long to settle out?
Don't like dealing with corn in general, but I use a pre-ground corn with a flour like consistency. Pros: saves time in grinding, mixes in well, better gravities than when I was milling it. Cons: It's still corn. Fermenting on the grain, everything into the still, but we have an agitator.
What would happen if you scooped off the cap when its floating on top? is the cap mostly unfermentable stuff?
The smaller you grind of course the longer it will take to settle out. You will never get a clear liquid but a milky yellowish liquid that has some very small particulates in it. Scooping the cap off I would not do. It is kept on top by the gasses from the fermentation. These will settle out within a couple hours after fermentation ends. We never get everything out but as grain swells when wet and will be larger and heavier. We get about 90% to 95% of the grain to settle out. Coop
According to The Alcohol Textbook (K.A. Jacques, T.P. Lyons, D.R. Kelsall), the fineness of the grind has a significant effect in final alcohol yield (which correlates, among other factors, to starting gravity). The difference in alcohol yield can be as much as 5-10% between a fine and course grain. A finer grind exposes more surface area. More surface area means the enzymes can better penetrate the kernel and convert your starches into sugars.
Aside from the fineness of the grain, you should check the following parameters as they can also affect starch to sugar conversion during cooking/mashing.
1) Temporary Hardness: Determined by the measurement of bicarbonates. Above 100 ppm is undesirable because of its contribution to alkalinity. Alkalinity inhibits the proper pH balance necessary during mashing, resulting in inadequate conversion of starch.
2) Calcium: Calcium ions aid in protecting alpha amylase from heat inactivation. Ideal between 50 and 150 ppm.
3) pH: Ideal between 5.2 and 5.5 for enzyme conversion.
we have cooked two more mashes with very good results by both grinding finer and cooking a little longer. the difference was 5% ish. how would we measure bicarbonates?
Get a water analysis test. Culligan did ours for free. You will get a detailed analysis of primary ions, secondary ions, pH, hardness, etc.
To clarify my previous post, I forgot to mention carbonate. Carbonate is more of a concern than bicarbonate. Carbonate, like bicarbonate, contributes to alkalinity and will counteract the beneficial effects of calcium (calcium reacts with phosphates in the mash and releases hydrogen ions, thus lowering the pH of the mash). Acidification of the mash is crucial in creating an environment that is ideal for the diastases. Bicarbonate has twice the buffering capacity of carbonate, but as long as you are boiling your mash, it will precipitate out as a solid. This is why its contribution to water is called Temporary Hardness.