Open Fermentation and/or Different Fermenter Geometry.

I was going to bump this thread, but it has tangents off to wild beer and coolships, so I'll start afresh.

https://www.thehomebrewforum.co.uk/threads/open-fermentation.67153/

Lets have a positive discussion, sharing of experience and resources regarding open fermentation. Who's doing it? Who's interested in trying it?


Getting the ball rolling, John Palmer is a good place to start.



As is Russian River.



Good enough for Timothy Taylor.



And Sierra Nevada, Schneider Weisse, Pilsner Urquell, Harvey's, Anchor Brewing. Arguably some of the most iconic brewers in the world, amongst many others that open ferment.



As explained in the Russian River video, an open top is just part of the story, and having a shallower depth of wort matters. Something Brasserie De La Senne and Brasserie Dupont insist is vital to the health of their yeast and quality of their beer.

This is a good article explaining the pathway of ester production and how fermenter geometry impacts that.

https://wildflowerbeer.com/blogs/blog/process-e1-primary-fermentation-geometry



Do you need a conical FV? or a lid and airlock on your FV?

https://beerandbrewing.com/4-reasons-to-try-open-fermentation/

I have tried it, it interests me. The main problem I had was temperature control. Bunging a open FV in a closed fridge seemed to defeat the object. I've noticed you use a stainless catering tray @Sadfield - getting hold of one of those and being able to heat it somehow is on my list of things to mess about with. I did brew an absolutely banging Kentucky Common using open fermentation once.

I started with a plastic box, in the brew fridge, but moved to the stainless which wouldn't fit in. To compensate I did buy a reptile/fish tank heating mat to run off a PID. It works, but I've found as the room temperature is pretty stable, and fermentation is exothermic, it is a bit redundant. If your brew area is pretty cold, it'd work well, though. I also find that downward temp control isn't as critical as off flavours are gassed off better, and yeast is healthier. I recently fermented a lager with Saflager S-189 to push the envelope, pitched at 19c it maxed out at 22.3C and was fine, obviously not a world class example, but passable. I think with the surface area it loses more heat.

My brewery is a single skinned garage with no roof insulation so it can get nippy in the winter. But I do have a few ideas. I'm right in the middle of a huge patio / pub / outside kitchen build at the moment so it will have to wait.

I do open fermentation for beer & wine.

But are we talking completely open or covered in some way (vented lid? Shower curtain) without airlock?

Sugar concentrations, shape & volume can affect the yeast physiology too. Reducing reproduction and ultimately affecting fermentation efficiency, esters, flavours etc. Osmotic stress on yeast is a thing.

The good news is typically homebrew volumes aren't enough to create an issue.

The shape of the fermenter really does make a difference. Wider than it is deep is a good rule of thumb and avoid tall fermentators

MashBag said:

But are we talking completely open or covered in some way (vented lid? Shower curtain) without airlock?

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I think, anything that allows a two way exchange of gases. CO2 out, oxygen in. The complete absence of back pressure.

Ignoring any myths about blankets of CO2.

https://beerandgardeningjournal.com/can-co2-form-a-blanket/

Sadfield said:

Ignoring any myths about blankets of CO2.

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Are we also ignoring the myths about gas flushing?

When I toured the Czech breweries and also the pub brewers they each only fermented with open fermenters. The brewery I most wanted to see was close to the German border but it was closed. It did reopen again but has closed permanently now. The fermentation was carried out in wooden barrels but seems to have changed to stainless steel after the first closing.
https://allaboutbeer.com/secrets-czech-brewing/

https://www.facebook.com/share/r/etLDjbHJt3FfzhFe/?mibextid=UalRPS

Well there is no myth of CO2 blanket....it is real...stick your head in a fermenter post fermentation and see how long you last - actually don't obviously, but I have and was instantly unable to breath and would have been overcome in a matter of seconds if i'l left my head in there....even when the lid was left off the fermenter for 20 or 30 mins it was still deadly...it would have taken hours for air to diffuse into that space and dilute the CO2 to any levels that wasn't dangerous.

Also my time as an apprentice on an aircraft assembly line saw me scuttling through small holes inside the wings to carry out various jobs to the systems that are in there...a classic job for apprentices who are small enough to fit inside...we had to wear CO2 alarms at the lowest part of our bodys due to a build up of CO2 from breathing that lulled you into a false sense of security as it dropped to the floor , built up in concentration and eventually filled the space from the bottom to the top and without the alarm it would have been too late to get out of the space before being overcome by the gas so needed as early alarm as possible if CO2 levels became dangerous. So CO2 is very very deadly in confined spaces and it does fall to the lowest point to form the highest concentrations if in an enclosed confined space.

Also another snippet of evidence..I recall seeing a BBC documentary on dinosaurs many years ago investigating a unique and unusual site of a whole herd of dinosaurs of all ages who all appeared to have died at exactly the same time....the primary hypothesis was that a nearby volcano vent was expressing CO2 which lay on the bottom of the ground and washed over the ground like water flooding a plain for several miles in all directions and a nearby herd of hebivour dinosaurs were grazing and dipping their heads into the couple of feet deep 'pool' of CO2 lying on the ground and they were all overcome, collapsed and asphyxiated to death. So another example of a CO2 blanket and this time in open space literally behaving like a blanket.

I visited a friend of a friends up in Yorkshire who had his own brewery for a tour and was using open top fermenters...his first job every morning was to climb up a ladder and scoop out the dead flies floating on top of the Krausen that has become overcome by CO2 flying over the top of the open fermenters. So if you're going to do it then make sure its in a nice semi-sterile environment...not sure my garage would be a suitable place.

So if you have yeast off gassing CO2 into a confined space it wont take long before air is purged out of that headspace and the concentrations of air will drop to very very low levels measured in the parts per billion or even less...to all intents and purposes pure CO2.

Think this issue about open fermenters and oxygen exposure is a myth - even with open fermentation keeping air away from the beer is important...there are a series of short Timothy Taylors videos on YouTube documenting their process of brewing and they use open fermenters...they specifically mention the krausen protecting the beer underneath from air and they drain off the beer from underneath before the krausen fully subsides to avoid any contact with air and fermentation is finished in enclosed vessels or barrels.

But its a traditional method and I like tradition...I reamain to be convinced it actually impacts flavour or any detectable aspect of the beer, but hard to get a back to back of the same beer brewed in parallel in different fermentation vessels. Recently Molson Coors, formerly Bass, ditched their famous Burton Union system that was supposed to impart a unique flavour to the beer, for more modern and efficient (and cheaper) fermenting process and the old fellas down my local who've been drinking Bass for 40 years and wont let a drop of sub standard Bass pass their lips don't seem to have batted an eyelid. So I remain suspicions that the actual vessel beer is fermented in impacts flavour so long as the yeast is happy and has plenty of nutrient available, and air is kept well away post fermentation. But I also remain curious and ready to be convinced. I mean there are plenty of people who've fermented beer in plastic buckets and transitioned to stainless vessels and if the vessel had a significant impact then it would be widely accepted and known by now.

Anyway I'm planning a trip down to the Thornbridge tap room soon. Thornbridge have recently bought a Burton Union set from Molson Coors to save it from being scrapped and preserving a small slice of British beer brewing heritage, so hopefully will be able to try Jaipur brewed on the Burton Union system against the normal Jaipur brewed in modern conical fermenters to see if there is any difference. They say its exactly the same recipe so any difference should be down to the fermentation method.

hoppyscotty said:

the old fellas down my local who've been drinking Bass for 40 years and wont let a drop of sub standard Bass pass their lips don't seem to have batted an eyelid.

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So they didn't notice the change when Molson Coors let the Bass yeast strain die out then? At least according to a friend who works for them.
Bass was the beer of choice for us (and pedigree) back in the seventies and when kept and served correctly was a brilliant pint, there is still the odd pub that keeps a barrel (in the back) with a tap to directly fill the glass. No crappy sparklet, no head just pure Draught Bass.

hoppyscotty said:

Anyway I'm planning a trip down to the Thornbridge tap room soon.

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I live very close to Thornbridge and yet to have a drink there, I must visit once the Burton Union set goes in, they have gone up in my estimation since saving that.

hoppyscotty said:

So I remain suspicions that the actual vessel beer is fermented in impacts flavour so long as the yeast is happy and has plenty of nutrient available, and air is kept well away post fermentation.

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Here's a famous example.

"By fairly reliable accounts, the beer hasn’t changed much over the nearly 90 years since it was first brewed. One of the largest changes came in 2007, when Orval expanded and renovated the brewery and replaced open fermenters—oh hey, that’s classically British as well—with cylindro-conicals. It took them three years, starting in 2004, to figure out how to use those tanks without losing the character the open fermenters gave."

https://www.beervanablog.com/beervana/2020/4/27/making-of-a-classic-orval

Another example is Duponts famous stalling yeast. Their FV are one meter deep, yet other brewers struggle with it.

Then there's Sierra Nevada and Russian River that operate both Open and CCF in newly built breweries.

A blog on how geometry matters.

https://edsbeer.blogspot.com/2018/07/fermenter-geometry.html?m=1

From that I asked Ed on twitter if applied at a homebrew scale (the deleted tweet, from quiting X), the brief exchange got an interesting reply from one of Heriot Watts professors.

hoppyscotty said:
the old fellas down my local who've been drinking Bass for 40 years and wont let a drop of sub standard Bass pass their lips don't seem to have batted an eyelid.

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I would bleddy hope so with a lab the size of their's.

Fermenter geometry is studied.
The world ferments 100's of billions liters.

Do we really think industry is not investing in and investigating it, but rather just leaving it to chance?

Geometry matters.

Like @marshbrewer I've tried it, I'm interested.

I've fermented a couple of Hefeweizen's open with WY3068 - unfortunately the second one I left open too long and it oxidised, losing the balance of flavours.

More recently I fermented a porter open with WY1968 - it was good though I don't have any kind of comparison that tells me how it compares with a closed fermentation. WY1968 ferments fast, though to be fair I probably chickened out and put the lid on a day or so earlier than I maybe needed to.

Maybe it's just me but I was surprised to find references to open fermentation in German brewing - a (translated!) German article I found on Hefeweizens suggested open fermentation and Jamil Zainasheff will literally bang on for hours about open fermenting Dusseldorf Altbiers to get the right flavour profile.

Speaking of which, I'm planning in the autumn to have a go at a Dusseldorf Altbier which I'll try fermenting open with K-97.

One area where I have a concern is around oxidation - I don't think I'm in a rush to open ferment a heavily dry-hopped IPA, but all beers are susceptible to oxidation to some degree. I'm curious @Sadfield , how do you guard against oxidation if you're fermenting, say, a bitter in your stainless catering bins?

Up to now I think I've just fermented with the FV lid (I use plastic buckets) displaced, ready to snap it shut tight when I think the time is right - I leave it in the brew fridge with the door shut (pic of the porter here)

The flip side is I get the impression that to some degree in an old fashioned (?) setup like double drop or a Burton union they'd open ferment but then move to a closed (?) vessel (brite tank? straight to wooden casks???) where there was enough residual yeast to carry on cleaning up off flavours and scavenge any oxygen pcked up (I may be totally wrong about this!).

I have no problem with the idea of fermenting in shallow (or not) catering bins, I quite like the simplicity of it, I'm just not clear how you go from there to some intermediate secondary/brite tank vessel (if that's even needed) to packaged beer in a keg.

Most of the time once there's sign that the krausen is about to drop, rack the beer into a purged corny keg via a tap on the bottom of the FV. Letting it ferment out. Occasionally, I'll just put the stainless lid on.

I could also drop after 16 hrs and replicate another method of British brewing, the Double Drop system, used by Brakspear.

I can see the point of this if you want to encourage some wild fermentation (eg open bucket of wort under fruit trees) but can’t think why I would want to do it for my regular beers - my closed fermenter works fine (if it ain’t broke…).

hoppyscotty said:

Well there is no myth of CO2 blanket....it is real...stick your head in a fermenter post fermentation and see how long you last

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Absolutely agree, but you do seem to have gone a bit ott. If you don't mind me saying so.

CO2 isn't intrinsically poisonous.
It's heavier than air. And replaces the oxygen you need for respiration.

It normally makes you cough first.
Also consider that the yeast produce the same amount of CO2 even with an airlock, so your exposure is the same.

And at 23l batch size, it is defo worth understanding, but not a vast amount.

Just adding a little balance, not disagreeing with you.

OTT and wrong. If CO2 is dispersing into the air, then by the same argument air must be dispersing into the CO2 above the wort. The yeast can scavenge that oxygen.

MashBag said:

CO2 isn't intrinsically poisonous.
It's heavier than air. And replaces the oxygen you need for respiration.

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If CO2 formed a blanket due to being heavier than oxygen, sunbathers would suffocate on beaches. It's a myth. What does happen with open fermentation is there's upward off gassing of CO2 that is slowly dispersing into the atmosphere.

Here's the article again.

https://beerandgardeningjournal.com/can-co2-form-a-blanket/

I’d do it (although if I fermented in the brew shed I’d have to have a cloth over it to prevent the robin that frequents from polluting it). Back bedroom I’d just do it. I’d probably let it ferment out too and bottle straight from it. Happy to report back.

Sadfield said:

OTT and wrong. If CO2 is dispersing into the air, then by the same argument air must be dispersing into the CO2 above the wort. The yeast can scavenge that oxygen.

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Nah..
What you speaking of is the confinement not the gas. Or gas flushing.

But Co2 is being produced by the yeast and sits (heavily) on top. End.

Due to containment and volume it will escape /overflow. Through the airlock, over the side through vents in lids.