Fermenter Geometry

It's a while since I've done a post about technical beer nerdery, what with more important things getting in the way. But I think I've slowly reached an understanding about why fermenter geometry is significant so it's time for another.

It's a term used in text books, usually shortly before launching into descriptions of the various weird and wonderful types. Yorkshire Squares and Burton Unions often get a mention, and what the hell was going on Spherical fermenters? Most beer is made in cylindro-conical fermenters though nowadays.

Obviously yeast collection techniques will differ with different shaped fermenters, Ale yeast traditionally skimmed off the top, lager yeast scrapped out the bottom. With cylindro-conical fermenters the yeast sediment can be drawn off from the bottom of the cone and they are now commonly used for both ale and lager brewing. 

But that's not really what I was interested in. I wanted to know what does the fermenter shape do to the beer flavour. Having started out as a microbiologist I know that bugs don't read the text books so will at times behave strangely, but how does the shape of a fermenter affect this? It seems the main difference between different fermenter types is not so much due to the shape as due to the depth of the wort.

Traditional fermenters are quite shallow and lager maturation was carried out in horizontal tanks so not much depth of wort.

Not deep

As cylindro-conical fermenters are often big...very big (6000hl)...they can get very tall too. Up to 15m apparently (and even 40m if used for maturation/conditioning).

Deep

Greater depth means greater hydrostatic pressure which affects how the fermentation progresses. Carbon dioxide concentration increases resulting in greater mixing of wort due to gas lift. As the height to diameter ratio increases, so does natural agitation and the fermentation rate. This rapid fermentation can mean medium gravity ales can be produced with unseemly haste (30 to 49 hours). Beers made rapidly in tall fermenters with higher pressure contain less esters, as these figures for ethyl acetate show:

Ethyl acetate content of beer resulting from shallow and deep fermentation
Wort height (m) Ethyl acetate (mg/l)
3                        20
18                      12

This demonstrates how putting the same wort into different fermenters can make different beers. There are other factors that affect ester production during fermentation so things such as oxgenation rate, temperature and pressure can be adjusted to compensate.

I also recently learnt that greater surface area at the top of the fermenter means greater loss of hop volatiles if dry hopping in tank. As one of the purposes of traditional lagering is to get rid of unwanted volatiles will it also have an effect there? Certainly horizontal tanks were favoured over vertical ones. There may be more mysteries to fermenter geometry yet.

A visit to Harvey's Brewery

After the warm up at Burning Sky the main event was at Harvey's the next day. We were meeting at 11 am in the brewery tap before the BHS AGM at noon. Or at least that was the plan but a couple of leisurely pints of mild before getting down to business was not to be for me. A points failure meant my train slowly sauntered south and there was only time for a swifty before things kicked off.

Despite running late I stopped to take the obligatory photo of the brewery from the bridge in Lewes, correctly assuming that by the time I staggered back I'd completely forget about it.

Good, innit?

Though not quite up to IBD speed standards the AGM was mercifully brief. If only the committee meetings were like that.

If the BHS embraced keg beer there'd probably be more young people or something

A tour of the listed brewery followed the AGM

The extension to the tower only dates from the 80s though

We heard more from Head Brewer Miles Jenner before going inside:

He talked about when they were flooded. The tank behind him was ripped out of the concrete.

The flood level is marked by the plaque above the head of the gentleman on the right:

They still have a copper Copper, though it's relatively recent, dating from the 90s if I remember rightly. Miles was worried switching to all stainless steel might upset the yeast so replaced the old Copper with a new copper one.

They have a stainless Copper too.

and a steam engine they fire up once a year.

Old and new mash tuns too:

as well as a Sugar Dissolving Vessel with syrups and blocks of invert sugar:

This is where the sacks of malt enter the brewery:

Some of the hops come from The Hampton Estate so bear the Farnham bell.

A map on the wall from 1980 showed where hop farms were then:

Good old Bastard East Kent is there but shockingly no mention of Farnham.

This crime is then compounded by a diagram saying the Farnham bell is used for hops from Hampshire:

I believe all the hop farms in Hampshire are now gone, though the number of hop farms in the Farnham area in Surrey has recently doubled. Sadly only to two though.

Inside a mash tun

More of the copper Copper

They use open fermenters. The parachute shown below is used for yeast cropping. It can be lowered into the yeast head and the yeast runs into it and then down a pipe to where it can be collected below.

The gravity is given in Pounds Per Barrel, which I think makes it 48.6 in degrees Sacch. They still use Fahrenheit too.

Here's a parachute in an empty Fermenting Vessel, with an attemperator to cool the beer on the left, and what looks like some beer stone at the back.

Lots of dipsticks:

Harvey's are the only brewery in Britain to still use returnable bottles.

The 1948 chiller on the left

The recently returned to kegging to satisfy the demand of people who prefer beer that is not the pinnacle of the brewers art. They sell around a thousand barrels of keg a year.

The filler is from Lambrechts

As all good brewery tours do we ended in the sample room, where I'm delighted to say Tom Paine was on despite the fact we'd not quite reached July. I used to have a pilgrimage to Lewes with my dad every July to drink that beer.

The winner for beer of the day was Armada in the brewery tap though, but then the magic of cask beer is not something for mortals to understand.

A visit to Burning Sky brewery

As a warm up before the Brewery History Society AGM there was a visit to Burning Sky brewery. They don't normally do tours but Miles Jenner of Harvey's Brewery is our current president and he was able to organise it.

The brewery is based in a couple of barns.

The sky certainly was burning when we visited, though the name comes from a song by The Jam, one of Woking's finest exports*. Apparently the lyrics fitted with what was going on at Dark Star brewery, Burning Sky founder Mark Tranter's former employer.

It's a 15 barrel brewery...

...though it does have a few features that set it apart from the ordinary:

There's a hop rocket for dry hopping

And the mash tun is equipped with rakes for mixing when lambic style turbid mashes are made

There are foeders for maturing beer

A coolship for making lambic style beers

And wooden barrels filled with beer slowly fermenting away.

They do cask, keg and bottled beers.

We got to try a few of the bottles and I was particularly taken with Recusant, which has more than a touch of Orval about it. I'll definitely be getting more of it next time I see it.










* Don't listen to London imperialist Des De Moor when he tries to claim Paul Weller.

Coping with the CO2 crisis

As someone who not only drinks in the ways of righteousness but has extensive stocks of beer at home I've not been worried by the current shortage of CO2 in Europe. The good lord saw fit to make the production and serving of beer perfectly possible without the use of CO2 and god's chosen representatives on earth have taken the opportunity to re-state this point.This did, perhaps predictably, lead to howls of outrage from twerps on twitter but I care not one jot.

Though in these ecumenical times the denigration of other, lesser, types of beer is now prohibited this should not prevent the veneration of the one true living beer. The shortage of CO2 provides a good opportunity to to reflect on how god intended beer to be made and remember the importance of letting real ale into your life. And mouth.

No extraneous CO2 was used in the production or serving of these beers

Finings and beer flavour

More evidence has been published showing that isinglass finings do not affect beer flavour. The paper "Assessing the Impact of Finings on the Perception of Beer" details a comparison made of a beer in fined and unfined form.

Which do you prefer?

There is an almost religious belief in the superior flavour of unfined beer amongst some beer geeks, though I've not seen any research to back up this assertion. In fact the only evidence I've seen previous does not support this claim. And now there's more evidence against it.

One hundred and seventeen people blind tasted hazy unfined beer and bright fined beer in black cups, and 118 people tasted the same beers in clear glasses. Neither group found any difference in the taste. In fact the only difference found was that in the clear glasses people preferred the appearance of the fined beer.

I would still be interested to see more research on this topic, but there are now published papers showing a trained tasting panel, and large numbers of social drinkers, not finding any difference in flavour between fined and unfined beers. Clarity is emerging from the haze.

A talk on Farmhouse brewing by Lars Garshol

The second talk I went to at the London and Southeast Homebrewing Competition was by Lars Garshol about Farmhouse brewing. I'm a big fan of his blog AND he'd helped me nurture my soul so I was really looking forward to this. It's a shame that scribbled notes make less sense when you go back to them over a week later but I'll do my best.

Beer = Grain + Work

Farmhouse brewing goes back thousands of years and wherever people grow grains (rice, maize, barley...) they make beer.

So all of northern Europe should have farmhouse brewing traditions. Farmhouse ales would be found everywhere (except where wine can be made!).

It wasn't commercial brewing as everyone made it. Hops are a preservative so helped commercial beer to spread.

Craft, Industrial and Home brewing are one branch of beer history that is distinct from farm ales. The only technological advances in farm brewing have been metal vessels and hose pipes.

Four and a half years ago 

Kaupanger is in remote Norway.

The brewer was taught how to make traditional beer for his wedding in 1992. Norwegian farmhouse breweries are generally based on 150 litres as barrels were 144.

A fire is started to heat water to 80°C and make juniper tea. They split the branches lengthwise.

They mash at 72°C for two hours.

Wort separation is problematic so he puts a wire mesh on top of the branches and runs off slowly (25hl/hr)

He doesn't know what hops he uses.

The beer has no hop character anyway.

Juniper is the spice, not hops, so the beer has lots of juniper flavour and bitterness from the juniper.

The beer has a smoky, banana flavour, is 8-9% ABV and only 7 or so IBU.

Voss is 1000 km south.

It is not near the sea so was very isolated until the 1950s.

The wort is boiled for six hours, giving 50% evaporation. The wort darkens considerably!

Insects leave branches one or two days after they're picked.

The beer tastes of yeast and like and explosion in a marmalade factory!

The yeast is stored in the fridge for four to six months. It can generally be traced back to grandpa at best.

The yeast used to be dried on wooden rings for storage. Fermentation still starts in four hours!

The fermenter is insulated. They yeast is pitched at 39°C and rises to 43°C.

 This is typical in farm brewing.

Sigmund's yeast is three strains, all Saccharomyces cerevisiae.

Hornindal is also isolated, this time by a glacier.

The yeast is dried in flakes and bacteria are present, but the species is unknown.

The beer is not sour. It has flavour of tropical fruit, milky, mushroom and caramel.

They good flavour came when the yeast and bacteria were used.

They mash at 74°C and don't boil the wort.

The yeast is pitched at 30°C.

It gets going quickly as the brew is made on Saturday and a party is held on Monday evening!

No boil so no protein coagulation and no hops either. This give it a characteristic flavour.

I once made a 'malta' (unfermented beer) without boiling and when it went for testing Lactobacillus were found in it, so it's certainly possible for microorganisms to survive mashing.

Can't remember what was going on here

Next stop was Lithuania. Farmhouse brewers in Northern Lithuania mash with water not juniper infusion. 

They mash at 67°C, adding boiling water and grain until the mash paddle can't stand up.

After an hour the mash is put in an oven for three hours, where it boils and the sugar caramelises (tastes like honey!). 

It's filtered with wooden chips and straw. 100% pale malt but the beer is dark. It's fermented with baker's yeast.

Until 1850 you had to have your own yeast, mostly S.cerevisae, although one farm brewery used Brettanomyces. All are multi-strain. 

Kveik is very distinct from commercial yeast, and kveiks are split between those used in boiled and raw ales.

Kveik is domesticated. It is very thermotolerant and can be dried. The tropical fruit flavours they make can mean it tastes like you're drinking something made with American hops.

In Chuvashia (I think!) they call the yeast Gong, but sadly they don't brew in flying teapots.

The yeast is mixed with wort, sugar and white flour. They ferment at 39°C.

Kveiks are not POF+ (i.e. they don't produce phenolic flavour), other strange yeasts are. In North Lithuania where they brew more often than in Norway the yeasts are not drying resistant.

Farm brewing was carried out in Suffolk up until the 1950s.

Hot water was added in steps, which is a safer way to get the temperature right when you don't have a thermometer.

Yeast was shared around the village in a chain, like a ginger beer plant.

Farmhouse ales are the bigger half of brewing, in every details except volume!

It's a simple process that anyone can do, farmhouse brewers are not worried about details.

My notes end on "boiled wort came with metal kettles", which presumably was an answer to a question. And that ends my write up of Lars' excellent talk, which given the topic I can just squeeze into The Session #136, as the topic fits and I've been told I can get away with being a few days late.