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Corn Conversion Experiment

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Corn Conversion Experiment

Postby Bogdan » Mon Apr 22, 2013 3:58 am

I have decided that stirring big gloopy pots of boiling corn is no fun - I have been figuring I would build a mechanical. But I was reading an article about Saki production where they only soak the rice in hot water before using a mould to convert the starch and rely on a large portion of the conversion occurring during the fermentation stage. Having thought about this I decided it was worth giving the general principal a try with Corn to see what level of conversion I could achieve.

I started by reckoning that the best thing to soak the corn in would be hot backset because the acidity would do a a good job of breaking down the cellulose in the husk and other structural parts of the grain. So I took 12L of boiling backset and threw in 350g/L of corn and then insulated the pot well and allowed it to soak until the temp dropped to 65degC. When I removed the lid after 4 hours I found that the corn had absorbed almost all the water and that the corn seemed to be well broken down and gelatinous.

I then adjusted the pH to 4.5 and added Malted barley - 30% of the weight of the corn. Once again I insulated the pot and allowed it to sit until it had cooled to 38degC which took about 13 hours.

At this point I checked the and found that I had achieved 13.1 Brix which when I made some small adjustments to the volume for the increase caused by the liquefaction of the dissolved starch I calculated that I had achieved 65% conversion of the total starch content.

I have to say that even if I did not recover any more starch I would consider this degree of recovery acceptable since it was almost effort free compared with the problems of boiling and and stirring but I am almost sure I will get further conversion during the fermentation given that the enzymes are still active and the ferment is holding the temp up above 30degC. I used a dedicated whiskey yeast and a good dose of GA so we will see when the fermentation is finished if I got more conversion.

I figure it will only take a week or so to complete the fermentation at the rate it is working so I will do a determination of alcohol by distillation in my lab still and be able to work back to see what the total conversion ended up at. Will let you know the results as soon as I know.

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Re: Corn Conversion Experiment

Postby Bass » Mon Apr 22, 2013 10:11 am

Since you know the original gravity, you can just take a gravity reading when it's done then calculate ABV.

I'm a bit confused by something though. You wrote that you added the boiling backset to the corn then let it cool to 65C. Then adjusted pH, added the malt, and let it cool again to 65C which took 13 hours. Did you heat it up a second time? What temperature did you add the malt? I ask because one of the enzymes that you want active will start to denature at 65C and the other will start to denature at 69C
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Re: Corn Conversion Experiment

Postby zedzedtop » Mon Apr 22, 2013 2:01 pm

Think you are nearer to 50% extraction at that gravity... assuming that the corn is 0.8 DBFG. Maybe it isn't that high, but could be pretty close. Had you previously calculated the potential of the corn? Was this cracked corn?

The gravity reading will be affected by both the converted sugars and unconverted starches, and I don't imagine they affect the gravity in the same way. One doesn't really get an initial gravity reading with the sake process. If you are confident of the potential of your corn, you could ferment your experiment and then monitor the initial boiling point of the wash/mash. Then you know the ethanol% and as they say, 'the proof is in the pudding.'
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Re: Corn Conversion Experiment

Postby Bogdan » Mon Apr 22, 2013 6:11 pm

Sorry Bass
I screwed up the second Temp. (have edited it) I did not re heat I just let it cool to the yeast pitching temp.
So to recap - I added Cracked corn to boiling backset then when it had cooled to 65degC I added malted barley which I had ground to a course flour then I let it further cool to 38degC and pitched the yeast.

Hi Zedzedtop
I have little grain of brewing experience because my background is from the wine and distilling industry. I realise in the brewing world you have traditional ways of working out conversion efficiencies ( ie PPG) but I did not try to use this system due to my unfamiliarity. I did this by having a quick read around and deciding that hard dent corn which I am using is generally considered to have 70% total starch content by weight and I assumed the barley to be the same since the figures for that were similar. This meant that I had a total of of 4255g of grain with a max potential extractable starch content of 2978g. At the end of the second cooling period with the barley added I had 13.1 Brix which equates to 135 g/l of sugar and as close as I could figure it out by physically measuring the the displacement of a sample batch of corn and barley in water I now had an actual liquid volume of 14L which was slightly more than my starting volume due to the dissolved starch and some washing water.
My calculation was therefore 135x14= 1890g total actual extraction so 1890 divided by 2978 gives .634 or 63.4%
If there is flaw in this line of reasoning then please tell me because it all seems fairly straight forward but I guess I could be making some obvious mistake that has escaped me.
I am interested in how you came up with a figure for conversion efficiency which is quite accurate if you use the starting vol I gave - obviously there is an easier way to do it than from first principals.
I figure the reason you came up with 50% rather than the 64% I got was you used the 12L I gave as my the initial volume not the increased volume that I mentioned but did not specify of 14L. ( The extra 2L is some dissolved starch and a bit of water I had to use to get the corn dregs out of the pot and into the fermenter)
Having said all that even if the conversion from just soaking was 50% I would have been happy (I really hate stirring) and I am still confident I will get further extraction during the ferment.
I have a laboratory set up that I use to do accurate determinations of alcohol in wine and I will run a litre when the ferment is finished and then work backwards with the calculation to see what the actual extraction was and how much extra happened during fermentation.
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Re: Corn Conversion Experiment

Postby zedzedtop » Mon Apr 22, 2013 6:48 pm

I pulled the chart from

http://braukaiser.com/wiki/index.php?ti ... Efficiency

which accounts for expansion from the sugar. You just need to know the initial water and grain quantities. The chart assumes 100% conversion, 0.8DBFG (37ppg), and I believe 4% moisture in the grain.

The ebulliometer ethanol % technique assumes that you are pretty close to dry, as in dry wine dry. Most of my grain washes drop to 0 on the hydrometer or a bit below, so I assume the method is valid.

I hear you - it's no fun stirring a huge pot of polenta! Haven't done corn in some time.
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Re: Corn Conversion Experiment

Postby Bogdan » Tue Apr 23, 2013 12:29 am

Thanks Zedzed.
I will read through that.
I am sure it will be useful to me.
Now I just need to finish the oil jacket on my boiler so I can distill on the grain and and life will be simple.
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Re: Corn Conversion Experiment

Postby jake_leg » Tue Apr 23, 2013 11:32 am

Did you account for the sugars in the malt in your calculations? I think that is how ZZT arrived at ~50%.

It could be lower than that, I think you could have converted say 80% of the malt and 40% of the corn.

But if you could get 50% conversion by this method I would think it pretty useful. Corn is cheap after all. Lactic souring is another way to get the initial pH down and it definitely helps break up the kernels. But the problem with lactic souring is that cold wet soured grain does not reach as high a temperature as dry grain when you add boiling water. So I have to steam it. And even then my efficiency has been low.

At least there is not much stirring with the steaming. I just hit it with a paint stirrer every now and then.
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Re: Corn Conversion Experiment

Postby Bogdan » Tue Apr 23, 2013 4:02 pm

Hi Jake. I made the assumption that the malt had the same percentage by weight of starch as Corn. I know this is not correct, corn is 65-76% and barley is 55-74% but the difference i not statistically significant. Clearly I have no way of knowing if I have preferentially converted more from the barley than the corn but in the bigger picture it is not important. I have a good record of how much alcohol I could get from a given amount of corn using the boiling method and when the ferment is complete I will find out how this method compares for alcohol produced per kg of corn. If I can achieve something like 75% of the amount I got by boiling then I would change to using this method since the loss of a small amount of corn is less important than the aggravation and time involved in boiling.
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Re: Corn Conversion Experiment

Postby jake_leg » Tue Apr 23, 2013 5:45 pm

I'm not arguing. Anything that makes corn easier is good with me.
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Re: Corn Conversion Experiment

Postby punkin » Tue Apr 23, 2013 9:18 pm

Down load Brewmate. It's free and will work out all your efficiencies for you.
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Re: Corn Conversion Experiment

Postby Bogdan » Tue Apr 23, 2013 9:49 pm

Thanks Punkin - Tried that but there is not a Mac version so it will not run on my computer. Bit of a pain since it seems like a good thing.
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Re: Corn Conversion Experiment

Postby Bass » Tue Apr 23, 2013 11:42 pm

Good luck not getting any lactic souring. I'm guessing its a typical part of whiskey washes since we do lower temp rests with no boil to keep enzymes active. 65c isn't enough to completely kill off lacto. It went nuts on the bourbon mash I've got going. No funk at all, but bitingly sour.
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Re: Corn Conversion Experiment

Postby Bogdan » Wed Apr 24, 2013 2:23 am

Hi Bass - A bit of Lactic would be fine with me and its bound to happen since I used some of my UJ grain bed as a starter culture.
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Re: Corn Conversion Experiment

Postby punkin » Wed Apr 24, 2013 3:51 pm

Bogdan wrote:Thanks Punkin - Tried that but there is not a Mac version so it will not run on my computer. Bit of a pain since it seems like a good thing.


That's a shame. Did you try emailing the author from his website? I've found he is a pretty helpfull, commuicative guy. He's active on the beer forum where i hang out and still updates the program. He may have a mac version in beta, or at the very least if he gets people requesting it, it may fire him up to do one.
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Re: Corn Conversion Experiment

Postby zedzedtop » Wed Apr 24, 2013 4:15 pm

Brewersfriend has several good calculators. It's an online thing so even works w/Linux.
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