Monday, 23 February 2009

Cellar Practice


Having deliberately set out to be controversial in the last post, perhaps it's time to reassert my belief in real ale. I expected some comments to my questions about cask breathers and I really enjoyed the considered responses. I probably expected more agitated comments but in reality it was a good debate.

Unfortunately my followers dropped from 18 to 17 today. I wonder if someone got upset. Well tough really, as Tandleman points out it's a difficult subject but one we should not shy away from.

Let me show you my little world where some of the magic happens. It's not that pretty but it's special, it's my cellar. This is where we really do cask condition our beers. I thought I might take the reader through some of my thoughts on cask conditioning without cask breathers.

Now, this is a special treat for my blog readers. I know it needs a coat of paint. You are my guests in here, just be nice boys and girls and don't pick fault.

The key secret to keeping cask ale good is reducing the amount of bacteria and oxygen getting to the beer and maintaining CO2 levels in the beer.

Firstly lets consider bacteria. Air contains bacteria, quite a lot actually. Letting air into the cask and coming into contact with the beer is bad news. As Ted and others said in the comments on my previous post there are filters that prevent any bacteria from coming into contact with the beer. We have one such filter, which we normally put on what we expect to be the slowest moving beer. We really need to buy more and put them on every cask.

The second enemy of cask beer is oxygen. Now there is some disagreement about the merits of oxidisation of beer. There is a school of thought that says oxidisation can improve certain beers. It certainly changes the characteristics of beers. Some beer drinkers detect oxidisation as a significant off flavour.

Oxidisation aside, most spoilage bacteria need oxygen to multiply. In the absence of oxygen they can't do a great deal of harm in the short period a cask is on sale. If we limit the amount of oxygen and bacteria getting at the beer then the beer will last longer before detectable off flavours occur.

Finally though, CO2 is the friend of cask beer. But if we concede that we are not going to add any by artificial means what can we do to ensure there is enough? In cask conditioned beer the residual fermentable sugars left over from primary fermentation are digested by yeast. Rather handily the yeast also uses up any oxygen that might be hanging around. This is good as we don't want any in our beer. So, during cask conditioning we eliminate oxygen and increase CO2. The level of CO2 we refer to as the level of condition. Sometimes people talk about volumes CO2 which effectively is a measure of fizziness. Too much fizziness in cask beer makes it difficult to dispense. Especially if you prefer the correct northern methods of dispense using a sparkler. Most cask beer is vented and allowed to gas off before dispense; Hard pegging the vent hole, to retain the valuable gas, once the correct level of carbonation is achieved.

On dispense of course this vent hole is opened to allow air into the cask. If we didn't do this the beer would end up under vacuum resulting in flat or under conditioned beer. If we are clever, and I admit sometimes I'm not, we replace the hard peg back in the vent hole when we are not serving beer to retain CO2 and prevent air entering the cask. If we are really clever, which clearly I am not, we buy race spiles or something similar. These are a one way valve that prevents CO2 escaping. Eventually too much air and bacteria get in and the beer spoils and CO2 escapes. The result is flat vinegar. The beer should be removed from sale long before this happens.

What perhaps disappointed me about the comments to my post was that no one picked up on the fact that much of the beer that is dispensed from casks is in fact not cask conditioned. To quote the CAMRA web site:
"Real ale is a beer brewed from traditional ingredients (malted barley, hops, water and yeast), matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide."
I repeat that much cask ale has very little secondary fermentation occurring in the cask. There is simply next to no yeast left in the beer. This is done to ensure the brewery has as fast a turn around on casks as possible by ensuring the beer does not need to be in the casks for long.

Perhaps this is not a problem. By this definition, providing some fermentation occurs in the cask then perhaps it's OK, but in reality most of this secondary fermentation happens in conditioning tanks in the brewery and not in the container from which it is dispensed. Moreover, it occurs under artificially added CO2

Beer that is racked straight from the fermenter, as is the case with my beer, has a good supply of yeast. Secondary fermentation does indeed happen in the cask and the beer is in the cask for at least a week and normally more than two weeks. The yeast uses up oxygen that helps prevent spoilage bacteria from growing. When all the oxygen is used up the secondary fermentation slows significantly as yeast cannot digest maltose easily in the absence of oxygen.

Once the cask is vented and the oxygen starts to come into contact with the beer the oxygen is used up in further fermentation maintaining condition in the beer. This also helps to inhibit oxidisation and bacteria growth by continuing to produce a natural blanket of CO2.

As a result, I find it is the beers that are not produced using conditioning tanks that keep better. The beers that have sufficient yeast and residual maltose tend to stay good for longer after the cask is vented. If we are to frown on the use of extraneous CO2 in our casks I think we should consider that perhaps conditioning tanks are not good either.

OK, that was a lot of technical stuff. I considered cutting it down but then thought damn it, there doesn't seem to be much on the interweb about cellar practice. If this is some help to someone then it's worth publishing the lot. If the reader disagrees with my points then feel free to comment, that's what it's all about. For the know-it-alls who have just had their intelligence insulted, I apologise.

Thanks must be extended to all my brewing mentors for this information. In particular Stuart at Foxfield and Mike Parker of Hesket Newmarket and Cask Marque.

12 comments:

Velky Al said...

A fascinating article and a nice insight into how a cellar should be run, much appreciated.

On a side note, my followers also dropped by one overnight, I wonder if it was the same person?

Ron Pattinson said...

I was interested in the bit about brewery conditioning tanks. Any idea when this practice started? It would explain the blandness of some Bitters.

Can anyone remember the Hull Brewery? They used to have ceramic cellar tanks in most of their pubs. There was quite a fuss about whether that counted as cask or not.

Conditioning at the brewery in tanks and racking beer that it is just about bright into casks and no secondary fermentation to speak of. This doesn't sound far away from the bright beer of the 1970's. That was brewery conditioned, filtered, but unpasteurised.

Jeff Pickthall said...

"the correct northern methods of dispense using a sparkler".

Surely that should read "the incorrect northern methods of dispense using a sparkler"

...ducks for cover...

Tandleman said...

Ron I'm pretty sure that CAMRA have a definition of what constitutes cask ale defined as live yeast cell count. This is an extract from the policy, though it doesn't drill down far enough. "CAMRA believes that the practice of filtering beer and then re-seeding it and selling it as cask-conditioned real ale is unacceptable unless there is sufficient live yeast and fermentable material in the cask to ensure a satisfactory secondary fermentation."

Beer from conditioning tanks should have no real problem meeting this criteria as long as it isn't filtered, but beer that has been tampered with might do.

Tandleman said...

PS Added CO2 before packaging is common in keg production. It wouldn't in my opinion be common in cask production, as the usual point to do so is at the stage when the beer has been filtered and is transferring to the bright beer tank for packaging.

Cask shouldn't be filtered in this way, but that's where we came in. What the likes of John Smith or Coors do for their limited (against total volume) cask production, I wouldn't like to say, but I'd reckon too, some rough filtering might take place in other cases otherwise it is hard to explain the lack of "bottoms" in some cask products. Of course they could just be leaving it in the conditioning tank longer, allowing more trub to drop out. A grey area in some cases, with no consistent practice happening I fear.

Woolpack Dave said...

"...it is hard to explain the lack of "bottoms" in some cask products. Of course they could just be leaving it in the conditioning tank longer, allowing more trub to drop out."

I think you just explained it. Bright beer, brewery conditioned. It doesn't have to be filtered.

Tim said...

What is the general opinion on fining in teh conditioning tank with isinglass or gelatine? usually settles out most trub to give a brightish beer withing 48 hours.

Woolpack Dave said...

Tim an interesting question. I don't know when finings are added when conditioning tanks are used. It has been suggested to me that I could add finings to the beer en mass in a separate tank before casking. It would improve consistency.

All beer will drop bright without finings if it is left long enough.

Brewers Union Local 180 said...

Thanks for the treatise. I wish I had had more time to learn about the cellaring issues the last few times I was over there. Where do you find time to write all this stuff - aren't you supposed to be running an inn?

I seem to have brought home workable knowledge of the art of getting the conditioning (mostly) right. But having the brewery onsite, I find that this takes place more in the back of the house, rather than the front, at the moment I decide to turn on the chiller in the fermenter after giving the fermenting beer a knowing look. We have had a few casks come out a little on the lively side, but that's nothing that a period of venting doesn't cure.

Regarding a little bit of oxidization [sic], I enjoy the subtle changes from day to day. My patrons, with their nascent appreciation of real ale, are beginning to notice "peak days", when their favorite pint is just right. I had a cask of bitter that was just starting to turn a couple of days ago, fortunately with only a few pints left in its belly, and we had an educational moment demonstrating to the willing exactly what that starts to taste like.

Andy said...

One of the reasons for the increased use of conditioning tanks is simply that they use up less space than the equivalent number of casks.

In addition if you do rack straight from primary fermentation you potentially have a problem where the initial casks may have too much yeast while casks near the end of the racking process may have too little yeast. Use of conditioning tanks can make this process easier as has been suggested to you Dave.

Auxiliary finings are ok in the conditioning tanks to help remove protein but Isinglass (which remove yeast) should only be used in the cask.

Woolpack Dave said...

Ted, I don't really know where I find the time. I haven't really got it.

Andy, thanks for the information.

I haven't found any problem with excess yeast in the cask. Mind you, I stillage the casks, or rather Alan my barman does, in plenty of time.

Surely too little yeast is going to be more of a problem with conditioning tanks?

Andy said...

Surely too little yeast is going to be more of a problem with conditioning tanks?

Yes your right Dave, thats why you would not want to use Isinglass in the conditioning tank.

If you rack direct from the fermenter you will probably find higher yeast counts in the first few casks and fewer in the end casks unless for example you half fill casks and then top them up in reverse order.
Using conditioning tanks should even this process out more naturaly when it comes time to rack to cask

Having said all that if racking straight from fermenter to cask works well for you then you probably have better things to do than fix something that ain't broken! If you were planning to increase capacity you may find conditoning tanks useful.