The mysterious villian known as tannin

[joelabe05]

So I've been lurking about this board for a couple years, working on making my beer, and knowledge, more refined. I've learned a lot more than I thought I would, but there has been a topic I see referred to quite a bit in several areas of this forum. It's the dreaded tannin extraction when brewing with steeping grains or mashing all grain. Everyone seems to know that tannins make your beer have the "pucker face taste," and many people have theories about pH, temperature, and bag squeezing being the cause.

I've read a little on what tannins actually are, but I've failed to find a definitive answer on how to detect them- in the home brewery environment, anyway. Has anybody looked at the science behind tannin extraction, or is everyone content with mashing at ~150F and mash out at 170F? Does measuring pH during mash out give you an indication of tannin presence? Is there another indicator?

- Background info -
I'm working on my process for BIAB and have been squeezing the @#$! out of the bag at mash out. People say that it's a bad idea, but no one can tell me why. I'm a naturally inquisitive type of person, so the "we do it this way because everyone else does it that way" doesn't really work for me. And no, I haven't encountered any bad astringent flavors in my beers with my current process...yet.

Any thoughts?

 

[Stevo2569]

I'm been wondering the same thing. I forget the thread and youtube link but there are several veterans who squezze their grain bags in BIAB and dont mention any tannin extraction. I myself have done Partial and Allgrain with squezzing or pressing with no ill efffects. The Kaiser could definitely answer the question.

 

[rycov]

i think the thought is since you're getting more liquid out of the grains than you would have normally that you could be getting liquid that you don't want. i don't think its really an issue. i don't know, i'm not a scientist, but wtf? why would that extract tannins? i have never done a BIAB, but when i was doing extract with steeping, i squeezed my bag... er, i mean grain bag, and never got any tannins.

 

[BigEd]

The extraction of unwanted tannins from grain requires two conditions: high pH (6+) and high temperature (+180F). They will not be in solution otherwise. Squeezing a grain bag isn't going to release excessive tannins unless those two conditions have been met. However, that doesn't mean it's a good idea as you are going to squeeze out additional compounds (gums, proteins, particulate matter, etc) that would ordinarily be left in the grain that you really don't want in the beer.

 

[rycov]

However, that doesn't mean it's a good idea as you are going to squeeze out additional compounds (gums, proteins, particulate matter, etc) that would ordinarily be left in the grain and you really don't want in the beer.

this seems like a better argument for why not to squeeze. again, i don't know anything about it, but its much more logically pleasing.

 

[Yooper]

The extraction of unwanted tannins from grain requires two conditions: high pH (6+) and high temperature (+180F). They will not be in solution otherwise. Squeezing a grain bag isn't going to release excessive tannins unless those two conditions have been met. However, that doesn't mean it's a good idea as you are going to squeeze out additional compounds (gums, proteins, particulate matter, etc) that would ordinarily be left in the grain and you really don't want in the beer.

I agree. Also, consider that there is some tannin already in the beer, but it's not an "unwanted tannin" level. If you make beer, you should have some tannins in the beer from both the malt and the hops. It's the "excess" tannins that you don't want to extract!

 

[Malticulous]

I've found that it has much more to do with pH than anything else.

 

[BigEd]

I've found that it has much more to do with pH than anything else.

Probably true. When I have tasted beer that was tannic it was typically in a brewpub where I suspected the ownership trying to make 7 BBL of beer with 6 BBL worth of ingredients and making up the volume by oversparging.

 

[ajdelange]

http://www.beerandloafing.org/hbd/fetch.php?id=40273 should get you started. Steve also wrote an excellent article on the subject for Brewing Techniques. It's not on their website but if you can find a copy of the particular issue it will be worth your while.

There is a simple test for phenols in which they are complexed with ferric ions to give a red color. This is usually read in a photometer for a quantitative determination but I suppose you could use it without to get a qualitative answer the questions like "does squeezing the bag make extraction worse?"

 

[mabrungard]

I know of some commercial breweries that have a mashing system that actually compresses the grist at the end of sparging. So, I don't think that squeezing the grist is a strong cause of tannin extraction. I lean toward temperature, pH, and oversparging as the primary causes.

 

[wildwest450]

If excess temperature causes tannins to be extracted, please explain why decoctions work? I was under the impression it was ph related (above 6) as well.

I have also sparged well past the holy grail of .010 (.006) and not experienced tannins, my ph remained well within specs.

_

 

[ajdelange]

There are a couple of considerations here. First, the pH of decoction will be lower than the feared 6.0. Second, as the beer is decocted it is likely to be lagered. One of the main reasons for lagering is to give polyphenols opportunity to coalesce and precipitate out. OTOH wheat beers are (or were tradionally) not lagered and yet one doesn't experience the problems in flavor/mouthfeel associated with tanins. If you look at the URL I posted in #9 you'll see that Steve addresses this very question. It is, according to him, one of the mysteries of brewing science.

 

[coryforsenate]

pH is the main culprit behind tannin extraction. That's why beer that's been decoction mashed doesn't make you pucker up like eating an unripe blackberry.

When you oversparge, you'll dilute the ions in the mash tun and the pH will go above 6, hence the general rule of when the gravity of your runnings gets low you stop collecting. Of course, this also depends on your water's mineral content too, which is why some people can sparge to lower running gravities than others.

 

[audger]

If excess temperature causes tannins to be extracted, please explain why decoctions work?

to add to the above reason- you arent heating the grain, only the wort. the grain is where the tannins live. if, when you add the decoction back in, it brings the whole mash temperature above 180, you will extract tannins just like any other way.

 

[GuitarLord5000]

to add to the above reason- you arent heating the grain, only the wort. the grain is where the tannins live. if, when you add the decoction back in, it brings the whole mash temperature above 180, you will extract tannins just like any other way.

Just sayin is all, but every decoction I've ever heard of (with the exception of the mashout DC) is pulled from the thickest part of the mash. I.E. - The grain. So yes, the grain IS being heated to a boil.

 

[dan0804smith]

ah, tannins.

tannins are a base. have you ever over steeped tea? the reason why it is bitter is because tannins are released at high tempuraters.i think your best bet is to compensate for them. tannins are a base and are thus bitter. you can compensate for this bitterness by adding less hops. also try steeping at a lower temperature, or perhaps have a shorter final boil. you may also want to look into charcoal filtration as a way to remove some of the tannins. if worst comes to worst you could always neutralize the tannins (base) by useing a simple acid.

 

[Nateo]

I know of some commercial breweries that have a mashing system that actually compresses the grist at the end of sparging. So, I don't think that squeezing the grist is a strong cause of tannin extraction. I lean toward temperature, pH, and oversparging as the primary causes.

I agree that squeezing by itself is not the culprit, but it's important to note that breweries that squeeze their grains have pre-boil wort filtration systems.

I had a run of what seemed like tannic beers with the BIAB method after switching from a pretty fine cheesecloth to a paint strainer. The wort was heavily clouded. I was getting a good two inches of draff in the bottom of my kettle.

I switched to just lautering in the bag and vorlaufing, and it got rid of most of the cloudiness, draff, and bad flavor. Whether or not that was actually tannins is hard to say, but it sure tasted astringent.

 

[ajdelange]

ah, tannins.

tannins are a base.

Tannins are polyphenols and the mother of all phenols is phenol (C6H5OH) which is commonly known as carbolic acid. Polyphenols are just phenol groups linked one to another but what makes them phenols is that they have hydroxyl groups tied to aromatic rings. The hydrogens in those hydroxyl groups are loose, but not terribly loose (pKa 9.95 in phenol). The generic polyphenol we often speak of is tannin, also known as tannic acid.

tannins are a base and are thus bitter. you can compensate for this bitterness by adding less hops.

Don't think they are acidic and as they tend to complex out in lagering I wouldn't worry too much about extracting them. Hops and phenol bitterness are entirely different animals. Trying to offset any bitterness from them by reducing the hops charge doesn't seem like a very good idea to me. The best way to manage them is to lager and, if you want to decrease lagering time, keep runoff pH below 6.

if worst comes to worst you could always neutralize the tannins (base) by useing a simple acid.

Assuming that the hydrogens bound to polyphenols have approximately the same pK's as the parent phenol, nearly all the hydrogens are going to be bound at beer pH (i.e. 4.5 vs a pK of 10) and adding acid would only bind the few remaining free ones.


???

 

[Yooper]

to add to the above reason- you arent heating the grain, only the wort. the grain is where the tannins live. if, when you add the decoction back in, it brings the whole mash temperature above 180, you will extract tannins just like any other way.

It's exactly the opposite, actually. You are pulling the thickest part of the mash, and boiling the grain, not the wort. That's because a thick mash will have the pH of the mash- generally far below 6- and not extract tannins. The only time you would pull a thin mash would be to hit mash out temps.

 

[rayg]

Some random info on tannins for your enlightenment and edification:

From: "Effects of Protein-Polyphenol Interactions on Beverage Haze,
Stabilization, and Analysis" Siebert, K.J.
J. Agric. Food Chem., Vol. 47, 1999 353-362


"Protein-polyphenol interaction is important not just
in beverage haze. Dietary tannins (defined as water
soluble plant phenolic materials with molecular weight
>500 Daltons and the ability to precipitate
gelatin and other proteins from aqueous solution) have
an antinutritional effect (Mehansho et al., 1987; Baxter
et al., 1997). Tannins depress the growth rate of rodents
and chicks and decrease protein utilization in humans.
Hamsters are particularly sensitive to tannins, which
can be lethal to them in as little as 3 days."

So tannins aren't just polyphenols, they are large polyphenols.

From: "Polyphenols, Astringency and Proline-Rich Proteins
Luck, G. et. al. Phytochemistry 1994, 37, 357-371.

"Polyphenols (tannins) have a harsh astringent taste and
produce in the palate a feeling of roughness, dryness and
constriction [l]. According to Bate-Smith, and later
Swain and others [2,3] the primary reaction whereby
astringency develops is via precipitation of proteins and
mucopolysaccharides in the mucous secretions. Following
the classic experiments of Feeny [4,5] on the deleterious
effects of dietary tannins on the feeding of the larvae
of the winter moth (Operophtera brumatn) on oak the view
was formulated that tannins are uniquely a quantitative
defence. They repel predators by virtue of their strongly
astringent taste and because of their anti-nutritional
characteristics once ingested. Bate-Smith
[6] elegantly summarized their role in plant chemical
defence: “From the biological point of view the importance
of tannins in plants lies in their effectiveness as
repellents to predators, whether animal or microbial. In
either case the relevant property is astringency rendering
the tissues unpalatable by precipitating proteins or by
immobilizing enzymes, impeding invasion of the host by
the parasite.”

This paper also details the mode of binding of tannins to
proteins if you are interested.

Ray

 

[Saccharomyces]

One related side note -- if you happen to end up with a beer with tannins in it, fining it with PolyClar and racking after a few days will remove the tannins.

 

[Cellarbrau]

Your decoction close to the 1.010 range? I don't think so.