Saturday, May 14, 2011

Gas, and Hot Air

Our copy of "Beer" - the CAMRA magazine arrived today. It's so absorbent, it's always on our coffee table.

Anyhoo, onto the Cask v. Real Ale argument (It's quite clear-cut, surely, Real Ale is "matured by secondary fermentation in the container from which it is dispensed". And normally sucked rather than blown out like "keg" would be)

But, in an effort to clarify the situation, we asked our expert Professor Branestawm to explain the concept of "vols" of CO2 for us.

"Consider if you will Stringers", He began, "A pint of liquid which contains 1 vol of a gas dissolved in it. If we magically removed the liquid, we'd be left with the pint full of the gas."

OK, Professor, we've got that, but how does this help us understand the carbonation and maturation "histories" of the typical Cask v. the lovely Real Ale.

"It's simple", he exclaimed, and continued "Please note - what I say here is illustrative and assumes a few things (open fermenters for one), i.e. I've made these numbers up, so you'll have to take my word for it that they are about right!"

We'll take your word Professor, please, continue.

The professor pulled a scrap of paper from his pocket and flourished a curious and elaborate fountain pen. "My own design." he said, before rapidly drawing up the following table:
Vols CO2 in:
                         Cask           Real Ale
Start Fermentation         0              0      
End of Fermentation      ~0.8           ~0.8
Post Chill               ~0.5           ~0.5
Post tank conditioning    1.4             -
Into Cask                 1.4           ~0.5   
Out the door              1.4            1.4
On stillage (in pub)      1.5            1.5
On service (post venting) 1.1            1.1

"Which is to say", he went on, "Real develops at least two thirds of its condition (spending at least a week) in the container from which it's dispensed. i.e. it's predominantly Cask Conditioned, whereas Cask might pick up ten times less in cask. i.e. it's predominantly Tank Conditioned. i.e. Pretty much all of the secondary fermentation occurs in tank - not in the cask!"

Before we could say anything, he added, "Of course there's room for brewers to work in-between these extremes, tank conditioning up to, perhaps, 1 vol and finishing conditioning in cask."

But Professor, what's the problem with good beer being conditioned in tank, provided it's getting an appropriate period of maturation on its own yeast? Surely this is the key thing? And if tank conditioning makes this easier, why not?

"Well you see" said the Prof, leaning in conspiratorially, "this illuminates an issue with CAMRA's definition of Real Ale: Much of what is held to be the kind of beer that CAMRA is in favour of can only be called cask conditioned in a very narrow sense - some small amount of conditioning (secondary fermentation) in the cask is unavoidable when we're dealing with live yeast, but it's not an significant part of the production process."

We see Professor, but surely, brewers wouldn't call their beer Real Ale if it wasn't?

"Precisely!", cried the professor, "Only CAMRA ever called these things Real, the producers always called them Cask Ales, which they indisputably are, being ale and in cask!"

He smiled and shook his head. "They're not bloody stupid you know, these brewers!"

Many apologies to (the estate of the late) Norman Hunter.

7 comments:

Ed said...

I still haven't got my copy of Beer :-(

I'm not so bothered about whether the CO2 comes from a CT or cask, I want to know who's using filters and/or centrifuges for their cask beer.

HardKnott Dave said...

Mind you, if you can allow me to drop my vexatious litigant persona for a moment and instead be slightly contrary, there is still quite a lot of beer that does go through conditioning tanks that will still undergo some significant fermentation in cask.

I'd like to think my beer is in that category, although I worry it sometimes isn't.

StringersBeer said...

Ed, I don't know really - and I don't suppose it's the kind of thing most brewers would shout about. Although Fullers aren't so shy "After fermentation, all Fuller's beers are centrifuged to remove any excess yeast.", but what that means in terms of cell counts... You'd have to ask them.

Stuart Howe is on record as saying "Some of the larger regionals centrifuge [...] none render it bright."

Personally, I'm not that bothered. I don't believe it's any kind of fraud. I'm sure there are some lovely beers racked at 40 thousand cells/ml and some stinkers with 2 million.

StringersBeer said...

Dave, there's plenty of room (as the Professor says) between the extremes.

Birkonian said...

I'm not a brewer. To my surprise I got Grade 1 CSE in Chemistry. However, what I do know is that I prefer the taste of real ale to filtered/pasteurised beers.

StringersBeer said...

But Birko, things aren't so black and white. That's the point. Indeed, what you've set out there is a good example of the black-and-white fallacy.

The choice is not between Real Ale and "filtered/pasteurised". (Unless you're saying that all beer that isn't filtered/pasteurised is real ale, that's a false dilemma.) In reality, there are other sorts of beer, including rather-less-real "Cask" and the so-called "Craft Keg"

Some people like to think that CAMRA's definition of real ale is simple and clear cut. And perhaps it is, on paper. But, as applied, as the professor shows, it's not as simple as that.

Neil, Eating isn't Cheating said...

I've got nothing to add apart from to say this is an excellent blog post!

Very interesting stuff.

(thanks to Hardknott Dave for the link to this)