I've recently had a number of questions regarding brewing. Questions about how to convert corn into sugar to be fermented (queue banjo twang). Corn IS occasionally used in beer brewing, so I've got some insights I thought I'd share.
I've been brewing for a long damned time. Since 1980 - just a few short years after Nanny graciously allowed us to convert four freely available ingredients - water, malted grain, yeast and hops - into a bubblin' brew.
I've also dabbled in wines, mostly mead (honey-based wine) and ciders.
A key difference between my style of brewing, and that of most other folks is that I don't use kits. You can find a brew store online, and get a kit with the proper amount of malted barley syrup or powder. Add water, boil, add yeast and drink after it ferments and carbonates.
I go, 'old school'. I buy my malted grains, grind them, make a mash (converting grain starches into sugars), sparge the grains (rinsing the sugars from the grains in the mash), THEN boiling and everything else.
But what if malted grains weren't available? And what the hell is malting, anyways?! And I thought this was about corn!
Hold your water, sport.
Let's take a step back and understand the science behind brewing. All grains are made up primarily of starch. We want to turn that starch into fermentable sugars.
The starches are tightly bound at the molecular level. We've got to do something to open them up so we can convert them into sugars.
We have two paths to that goal: malting and gelatinization.
With malting, you take your grain - be it barley, corn, rice, rye, etc. - and soak it in warm water. You throw them into a sack and place them in a warm, dark place.
The grain begins to sprout. As it's doing this, the kernel is producing an enzyme called amylase. Amylase enzyme is what turns the starch into sugar.
Once the grain sprouts (different lengths for different grains, but about equal to the length of the kernel), you usually halt the growth process with heat (you don't want Mother Nature to take over and consume all of the starch). You roast the grain. A shorter duration roast gets you a light malt for a light Pilsner beer, and a longer roast will get you a dark malt for a heavier Stout beer.
Now, I said 'usually'. You can also just knock off the sprouts, grind up the grain, and begin your brewing. This is what is done very often with corn, for instance.
Now that we've got our malted grain, we're now ready for the mash to allow the amylase enzyme to convert the starch to sugar (more on this later).
The other option mentioned is gelatinization. Gelatinization uses heat and loosens up those tight molecular bonds on the starch so that we can add amylase enzyme to convert that starch to sugars.
Let's say you don't have access to whole corn kernels. All you have is corn meal. Or maybe you have whole corn, but you don't want to go through the time and hassle of turning it into malt (about a week).
You take your ground, unmalted grain (say, feed corn) or corn meal, and cook it. The temperature varies by grain. For corn, it's right around 170f. You add 1 pound of ground corn (like corn meal) and add 2 quarts of water. Bring it to temperature, constantly stirring. You'll end up with a thick corn mush (not mash). Think grits or polenta.
When you get to the 170f, you need to keep it there for about a half hour. You can just turn off the heat, cover it, and go get a cold adult beverage while you wait. You now have gelatinized corn.
Now, it's time to mash. Again, mashing is the process of adding a starchy grain to water, and adding amylase enzyme to get the starch to convert into fermentable sugar.
If we're using the malted corn that's just been malted (meaning it's still moist), we pulverize the corn, and add approximately 1 1/2 quarts of water for every pound of dry corn we started with. If we dried the malted corn for future use, we add 2 quarts of water per pound.
TEMPERATURE IS KEY HERE. If we bring this corn up above 165f, we'll deactivate the amylase enzyme that's present, and not get any sugar out of it. The sweet spot is between 145f and 160f.
A trick that beer brewers employ is to bring the water all by itself (no grain present) to slightly above your sweet spot, then turn off the heat. Add your grains, and the thermal mass of the grains will bring you to your sweet spot. For corn, I'd bring the water to 160f, then slowly add your pulverized corn while constantly stirring. You'll end up with a mush.
Cover your pot, wrap it in towels, and set your timer for 30 minutes. At that time, open the pot, give everything a nice stir, and cover it up again for another 30 minutes. You'll notice that the mush has gotten VERY soupy. That's the enzyme liquefying those long starch molecules into short, fermentable sugars.
If we're using gelatinized corn, we need to introduce the amylase enzyme. Two ways to do that: First, you can just buy the enzyme from virtually any homebrew store. Since we're goin' Old School, we're going to add a bit of malted grain (barley) to the gelatinized corn, and let nature do its biz.
So, our corn mush, looks like this after it's been gelatinized -
Think corn mush, polenta or grits. We need to add malted grain equal to between 25% and 30% of the original weight of the corn. BUT we need to bring the temperature down to 160f first (remember, we had this at 170f to gelatinize it). Take the lid off, stir every 10 minutes, and in a half hour, you should be down to 160f.
The grain you use needs to be cracked -
You can buy it just like this from a homebrew store. Since I brew a lot, I buy it in 25lb bags, uncracked (it lasts longer this way).
In this case, I started with 3lbs of corn meal, so I added 3/4 of a pound of 2-row pale malt barley (tip: If you only buy grain to do this, buy 6-row, as it has more amylase present, and will get you more sugar).
Cover this bad-boy up, wrap it in towels and set the time for a half hour -
After a half hour, give it a stir, then cover it up again for another half hour. Just like with the all-malted corn mash, you'll notice the mash has gotten very soupy. Nature!
After your hour mash, if you try and scoop up your stuff, this is what you'll get (compare this to the previous picture with the mush pre-mash) -
I'm going to use these corn squeezin's in an American Lager beer. Light body, low hops, high alcohol content.
Advanced, mind numbing stuff follows. Even some math. Proceed at your own peril.
Every grain has a given sugar potential. It's expressed as PPG - Points per Pound per Gallon. For instance, 1 pound of white sugar in 1 gallon of water has 46 points. On a beer hydrometer (a tool that measures the amount of sugar in your mash results), you'd see this as 1.046
It's a linear scale. Add two pounds of sugar to one gallon, and you'd have 92 points (46 x 2). This is important, as you want to know how much alcohol your brew is going to produce. The higher the points, the higher the alcohol content.
With grains, there is a little detour. Corn, for instance, has a PPG of 39. BUT, unlike already processed white sugar, it's virtually impossible to get every molecule of sugar out of the kernel. On average, you can expect to get about 75% efficiency from your mash. So, I'd expect to get only 29.25 PPG from my corn (39 x 75%).
So, in my example, I used 3 pounds of corn meal with 6 quarts (1.5 gallons) in my gelatinization. If I take my expected PPG (29.25) and multiply that by the 3 pounds of grain used, I get 87.75 points. Since I used 1 1/2 gallons of water, I need to divide this number by 1.5. That gives me 58.5 points.
If I take my mash results (called a wash or wort), I should see a reading right around that on my hydrometer. Well, well, well, lookee here!
If you do your mash in the low 150f range, and use 6-row malt, you could easily hit 80% or 85% efficiency.
Oh, and I heard once somewhere on the Interwebs that the grain bill for corn whiskey is 60% corn, 40% barley, or close enough to that.
One last thing: If you're going to use rice as your fermentable grain, its gelatinization needs to be at 195f. There are charts all over the Internet for the gelatinization temperatures of most grains. Corn and rice are both used in lots of commercial American lagers (Bud, Miller, et al) because they're cheaper than barley, and pack quite the punch per pound.
One more one last thing: If you're a wimp and don't want to gelatinize your own corn meal (hey, learn a skill, will ya?!), you can buy flaked maize from homebrew stores. It's corn that's already been gelatinized, and is just waiting for the addition of the amylase enzyme. At two bucks a pound, it's much more expensive than corn meal from the bulk section of your store, or feed corn from the feed store (make sure your feed corn is hormone- and pesticide-free).
As noted before, this corn juice is going into an American Light Lager. I'll let you know how it turns out.... in about 4 months! Cooler weather is lagering weather!
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