Education time! Tannins - what even are they?

[TimT]

For today's exercise in raising consciousness, attaining a higher state of being, and becoming one with the universal all, I thought I'd find out a little bit about tannins, a frequent ingredient in wine, cider, and sometimes beer . It's about time really because I've often advised others starting out in cider or meads "you'll need to get tannins in that" or "tannins will provide some balance". Without ever really knowing 100 per cent what the damn things are.

So, I took myself off to that fount of all wisdom and knowledge and benevolence, Wikipedia. It has this to say:

A tannin ... is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.

The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather. However, the term "tannin" by extension is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with various macromolecules.

Righto! So that clears that up then! Now that I know that, I just need to find out what "polyphenolic compounds", "proteins", "amino acids", "hydroxyls", "carboxyls" and "strong complexes with various macromolecules" are. Actually, I didn't have time to look all that up, but I did look up what seemed to me to be the most important terms: "polyphenolic"...

Polyphenols.... a structural class of... organic chemicals.... of large multiples of phenol structural units.

Well wank you very much, Dikypedia. So a phenol is....

Phenol, also known as carbolic acid, is an aromatic organic compound with the molecular formula C6H5OH.

A carboxyl.... well, we get redirected here:

A carboxylic acid /ˌkɑrbɒkˈsɪlɪk/ is an organic compound that contains a carboxyl group (CO2H).

A hydroxyl:

A hydroxyl is a chemical functional group containing an oxygen atom connected by a covalent bond to a hydrogen atom, a pairing that can be simply understood as a substructure of the water molecule.

Er.... and I'm not even drunk.

And as for "strong complexes with various macromolecules", I'm not even going to go there, as I'm a happily married man.

So there you go folks. That's what tannins are. So know that I know what they are, I still don't know what they are.

(Cross-posted at my blawg)

 

[Kudzu]

All I know (think I know) is that tannins are an organic compound that make a lot of river water in Tasmania brown. Helpful I know.

Speaking of which does anyone know the potential pitfalls of brewing with unfiltered tannin stained water? Hope that's not too off topic TimT.

 

[Airgead]

Yeah... the chemistry really doesn't matter too much. tannins are a class of polyphenol. Poly meaning many phenol being a class of chemical compounds with a particular structure. A polyphenol is a bunch of phenols stuck together.

The chemistry is really, really, super complex. I mean, seriously, PHd level organic chemistry if you get right into it. Don't go there

What is important is their impact of the wine. There are many polyphenols present but the tannins are the ones that give astringency (plus some other stuff). They provide some balance and complexity and also contribute to mouth feel.

The other important thing about tannins (and polyphenols in general) is that they are reactive so they will combine, split and recombine over and over in the wine depending on the conditions. Each time they react, they produce something new that changes the flavour of the wine. This leads to all sorts of interesting flavour changes. Astringent tannins will bond with other compounds to form large chunks that will then settle out and smooth the wine. Others will bond to form aromatics like vanilla and a bunch of other flavours associated with aged wine.

 

[TimT]

Speaking of which does anyone know the potential pitfalls of brewing with unfiltered tannin stained water?

I don't know about this; I'm sure you could give it a go and get some sort of a brew out of it. It depends a bit what you want to brew too; according to half-arsed half-minute of research on Wikipedia, tannins are often considered a fault in beer, with the exception of some styles such as the (sour, non-Saccharomyces Cerevisa-brewed Flanders Red). I occasionally try to impart tannins to my brews, especially when I think they can hold the astringent flavours: higher alcohol brews like stouts and porters, I think, would hold the tannins nicely.

 

[Kudzu]

The reason I ask is because the water at our new place is stained with what I'm pretty sure are tannins. Water is slightly brownish and doesn't seem to settle out if you leave to sit. I've brewed a bunch of batches since we moved (all pale beers) but none are ready yet. Haven't noticed anything off in fermenter samples.

 

[Mardoo]

Apparently one of the functions tannins play in plants which have them is to act as antioxidants, hence why they're so reactive (Briggs, "Malts and Malting"). And apparently I've been known to turn into an antioxidant when I'm drunk (My friends, December 26, 2008)

 

[TimT]

What have you got against oxidants? That's racist!

 

[Greg.L]

A couple of points.

Tannins react with the saliva in your mouth to give that furry mouthfeel we call astringency.

Polyphenols start as small units and join together over time to make larger units. Generally the smaller units are more bitter, the larger units more astringent so as wine or cider ages it gets less bitter. Young red wines can be quite bitter, good quality reds don't get released before 3 or 4 years of age. The larger units will eventually get so big they precipitate out, so good aged reds will have some deposit in the bottle.

 

[TimT]

The question that occurred to me was 'why are tannins typically associated with that astringent/mouth-puckering dry sensation'? I guess - though I could be wrong - it is because they tend to precipitate amino acids and alkaloids and/or the acids in their make up and/or something else entirely. Well! That's another question answered then hoorah!

 

[Mardoo]

I've been wondering lately what role tannins play in beer aging. There's a clear relationship in wine aging between tannins and fruit flavors. Big fruit flavors, no tannin, it won't age well. Big tannins, delicate fruit flavors, it won't age well. It's not a matter of simple 50/50 balance, but it's impossible to miss if you taste a lot of wine over time. (Taste, not drink )

So observing this got me wondering whether beers would age better with a bit more tannin in them. Would there be an advantage in mashing out at 90 degrees to increase tannin extraction if you wanted a beer to age a long time? Granted anthocyanins play a much greater role as antioxidants in wine. According to Briggs there are certain barleys that have been largely excluded from malting due to their anthocyanin level, but would they make beers that age better?

TimT and GregL, the point GL made about tannins is interesting as the mouthfeel of a wine's tannins changes with age. There are numerous descriptors in the wine world to describe the mouthfeel of tannins (chalky, over-extracted, powdery, drying, harsh all come to mind) which apply to specific feelings in the mouth.

 

[TimT]

I wasn't even aware 90 degrees is good for tannin extraction - it may be! There must have been a variety of old mashing techniques, and indeed ales that were drunk very fresh and ales that were aged over months or even years. But many traditional ales must have contained tannins - if for no other reason than that they were usually aged in oak barrels! (Indeed I think Saccharomyces Cerevisae finds one of its natural homes in oak).

 

[DJ_L3ThAL]

Mardoo you're blowing your n00b cover.

 

[TimT]

I usually try and get tannins in by chucking in cinnamon or oak chips or some such.

 

[Mutaneer]

^^ Great discussion,
and with some knowledge of complex organic chemistry from an engineering course a few years ago, I'm enlightened!!

Now to get onto pressing the 10kg of grapes a friendly local vintner has gifted me..

 

[DJ_L3ThAL]

If you BIAB, I've heard squeezing the grains can extract tannins held by the husks? If 90 degC extracts tannins, is this BIAB claim a myth or miscategorisation of tannins?

 

[TimT]

Hops have tannins too, they seem to be a pretty ubiquitous component of plants.

 

[MastersBrewery]

This leads to the question; what factor did tannins play in beer prior to steel and plastic as mashing and fermentation would have taken place in timber vessels, and most likely oak, and this is prior to any aging as such. So anyone care to build an oak mash tun? I think the results would be very interesting.

 

[Airgead]

Unless you are using new oak each time, the amount of tannin extraction will decrease with each batch you put through. Not just tannin of course... its all the other stuff in oak as well. Too much new oak can get a bit much (think horrible over oaked chardonnay) so winemakers tend to use a mix of old and new oak to get a balance. Or they go modern and use dominos/cubes/whatever

I suspect the amount of tannins from the oak would be less than the amount you get from the grains and hops. Especially if you use some dark roasted hops. Could be wrong though.

Cheers
Dave

 

[TimT]

Dunno about an oak mash tun - you'd have to put it on an open flame, yes?

Wouldn't oak barrels, at least for wine, tend to absorb tannins from the wine too? So in one sense their flavour would get sharper?

 

[Airgead]

Dunno about an oak mash tun - you'd have to put it on an open flame, yes?

Wouldn't oak barrels, at least for wine, tend to absorb tannins from the wine too? So in one sense their flavour would get sharper?

I don't put my plastic esky over an open flame...

Not sure about oak absorbing flavours from the wine. I'm sure it does but not sure how much of a factor it is. I suspect its minor as the alcohol in the wine will act as a solvent and draw stuff out of the wood but I could be wrong. I'll happily defer to the experts on that one.