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KevinM 04-23-2011 08:46 PM

Sorghum Astringency & Tannin removal
Correct me if I'm wrong, becuase I haven't managed to see the thread that had info.

I've been digging up things in the past few months about lowering tannin astringency when sorghum is used as a foodsource (or in our case brewsource). Pre-malt, there was some papers (which I can't seem to locate) that indicated a reduction in tannin when sorghum was soaked in a bicarbonate solution prior to sprouting.

Afterbrew, there are indications that some clarifiers which interact with tannin (gelatin/gelatine, egg white and Isinglass) will reduce tannin content in the wine/beer as well as clarifying.

I've done some searches in here on that as well, and pulled up things on improved clarity with some references to less "sorghum twang".

Has anyone been able to do any tests with something like this?

Nateo 04-24-2011 03:34 AM

Brew science is an incredibly lacking discipline. There hasn't even been much research done on hop isomerization and bittering, let alone more esoteric questions like sorghum astringency. Sounds like a good opportunity to do some research on your own.

You've mentioned the traditional ways of reducing astringency already. Are you having specific astringency problems with your sorghum brews? I've found that simple cold-conditioning helps reduce astringency.

KevinM 04-26-2011 03:10 AM

Both an artform and a science with a bit more weight on the art side, eh? There are quite a few papers on sorghum tannin content and the reduction methods outside of brewing. (I just wish I saved the pdfs somewhere.)

It does appear that there's been research on certain hop compounds that break down during the aging period at least. Perhaps sometime there will be more research on sorghum, however, in the meantime there's us.

I don't believe that I'm having any more of an astringency problem than anyone else actually. (And I'll be honest, there's some sort of obsessive tic I have about figuring things out. I'm not even that much of a beer drinker compared to wine & hard liquor).

But after digging through papers, I've been wondering about any potential link between the astringency we often speak of and the tannin content, as well as the composition of the actual tannins. There's papers that talk about differences in tannin structure, but nothing ever definitely saying anything that I could access.

I'll certainly be trying things out when I can, but I just don't have the situation where I can do the repeated comparative tests that I'd prefer between testing out
1) The malting methods were an alkali solution is used to soak the sorghum first to decrease resulting tannin and polyphenols.
2) The tannin reduction methods using
a) gelatin
b) egg white
c) isinglass
3) cold crash
As well as intermixed methods. I rather expect that the alkali solution would be the first process, followed by the addition of a subsequent fining agent.

I've found that cold conditioning has helped a bit as well, and others have mentioned some of the fining agents and there's info out there that says that it does react with the tannin, but I just can't find if any of us have tested anything and what their results were.

Nateo 04-26-2011 04:05 AM

Tannins aren't all bad. Some tannins provide body and "structure" and complexity to brew. For instance, when you oak age something, you're introducing good tannins. Astringency is just one side-effect of some tannins.

KevinM 04-26-2011 04:27 AM

That's true. That's the downside of too much tannin removal. Not to mention, what we call tannins appears to be a rather generic term for quite a few polyphenolic compounds and we can't just say "Hey you, the tannin on the left. Get out of here." While keeping the others that we do want in order to get some sort of tannin balance.

If I recall correctly, there were twice the number of reported flavanoids in sorghum but I actually want to say the overall tannin content was actually less than barley. It could be a juggling act of sorts, remove one group of tannins and replace it with a different set. I'm not a chemist, I'm kinda hoping one of you is.

All I can do is suggest and try it out myself and we can compare different results.

dorklord 04-26-2011 01:19 PM

Well, it seems to me that if you want to do a test, the easiest way would be to do make a batch, let it ferment out, then split it into 2 secondaries, and one secondary, just let it sit, on the other, use gelatin, then cold crash.

Bottle 'em up, and see what you have. You should have all of the other variables fixed as well as possible, since every other step of the process is the same, and both batches will have been aged the same time and exposed to the same environment (up to the point where you cold-crash).

The problem then would be that you'd need to do some blind taste-testing on the final product. At this point, it would be helpful to know a beer tasting judge or some such...

KevinM 04-26-2011 06:35 PM

Yeah, I can set up multitudes of tests, but it would really help if someone who knew what they were doing and what taste was actually being acheived did this. As well as the room and temperature to be able to keep control sets vs variable sets.

I just don't have the room, or the temperature control right now. Preferably I'd have a lab with plenty of room to do 5 gallons in single gallon bottles but to keep the same process for those 5, and then compare it to a separate 5.

Anyone doing any research papers have access to a laboratory and need a topic? :D

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