Thoughts on Open Fermentation

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SFC Rudy

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I was lucky enough to be stationed in Germany for nine years and I love a good German Hefe Weizen, especially when you swirl the yeast in the bottom of the bottle and pour it in…..”smack, smack mmmmmm, beer” Anyway;

Some background: I’ve brewed a few five gallon batches and fermented with Imperial Organic yeast G01 Stefon. The first one was fermented in a 7.9 gallon fermenter and it blew all the yeast out of the air lock. I essentially made a krystall weizen.

The next batch I did an open fermentation in a 10 gallon plastic wine fermenter. I put a nylon bucket cover on top then placed the (loose fitting) lid on. Good thing because the krausen actually made it to the top of the fermenter and was stopped by the nylon. Fermented for about three days then transferred to secondary then to keg. Turned out pretty good.

Brewed again yesterday, fermenting away in my chest freezer. The two issues with open fermentation are contamination and oxidation.

- My thinking is that the nylon bag and lid should stop virtually all contamination from falling in the top. I’ll skim the trub off the top of the krausen so I can retain the yeast.



- Oxidation. I know about the ideal gas law. My freezer is full of CO2; I can light my lighter and it will extinguish the flame when it reaches the lip of the freezer. Any thoughts on leaving the beer in the fermenter until packaging instead of transferring to secondary? My thinking is if I keep the freezer lid closed after fermentation slows, very little oxygen will infiltrate the freezer while waiting for fermentation to finish.



- Yes, I could use a blow off tube in my 7.9 gal fermenter, but I’ll lose most of the yeast. And I’m too lazy to install a tube big enough to accommodate the fermentation. That and I have a 10 gallon wine fermenter sitting in the corner collecting dust, why not use it.

Prost!
Rudy
 

RPh_Guy

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Seems like the point of open fermentation is increased oxygen exposure during fermentation, and bragging rights for having used a "traditional" method.

Oxygen:
I prefer non-oxidized beer, so I wouldn't ever want to do an open fermentation. I don't believe the freezer will be effectively purged, and if it does, then it's not really open fermentation, it's closed fermentation with lots of headspace.

Contamination:
Since you're covering it, contamination risk is probably fairly low. If you want an open fermentation without contamination risk, pump filtered air into the headspace.

Krausen:
I use Foam Control (AKA Fermcap-S), which helps keep krausen under control, along with underpitching and underaerating. Also I ferment in the mid 60s (WLP300). Krausen doesn't grow more than a few inches.
I bottle condition, so there's plenty of yeast in every bottle. Use low calcium water (like 30-40ppm) to minimize flocculation.
My results are fantastic for my taste, better than any commercial hefeweizen I've had except maybe weihenstephaner when I can get it fresh, rarely.
This is one of my favorite styles. I'm getting thirsty just thinking about it.
Cheers.
 

CascadesBrewer

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As far as oxidation, freezer and open fermentation goes...I can only add one anecdote.

I made 3 one gal batches of hop samplers. I have 2 small plastic fermenters and I have been playing around with fermenters made from small stainless steel pots. I was having issues with getting the lid seal on the stainless pot fermenter so I just moved forward with the lid clamped on thinking that would be good enough. After a 2 week fermentation session with all 3 sitting in my freezer (it is a very small freezer), the batch in the stainless pot came out oxidized...it is darker than the others and has a noticeable sweet/cardboard flavor I associate with oxidation.
 

ESBrewer

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I wouldn't leave it open in the freezer post fermentation. It is simple to rack from the bottom when the krausen is going down but a full layer of foam still sits on top. Leave the krausen behind then minimize the head space in closed secondary and let it finish. Bottle/keg soon when it has finished.
 
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SFC Rudy

SFC Rudy

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Last week my 10yo daughter came to me with a simple math problem. I cajoled the answer out of her. When she realized what she was doing she said "I sometimes over think things." And I told her "Yep, just like your dad."
 

deadwolfbones

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fwiw, it's not just German brewers that do open fermentation. Sierra Nevada still does it for Bigfoot and some other beers:


Have to say Bigfoot has never tasted particularly oxidized to me.
 

MakeDankBeer

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fwiw, it's not just German brewers that do open fermentation. Sierra Nevada still does it for Bigfoot and some other beers:


Have to say Bigfoot has never tasted particularly oxidized to me.
I believe the latest batch of russian rivers - "pliny the younger" was also open fermented. Which generated supposedly $3.3 million dollars.
 

RPh_Guy

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Commercial open fermentation is different because the fermenter geometry radically changes. They use shallow vessels for open fermenting, which puts less pressure on the yeast.

The same doesn't apply to home brewing.
 

CascadesBrewer

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Honestly I have not quite figured out the appeal of open fermentation. I know at the homebrew level, "open fermentation" is more like "vented fermentation". It seems like you have to either cap the fermenter or move the beer into a sealed fermenter after a few days to avoid oxidation. What am I missing? I can understand the open fermenters at a place like Cantillon or how large shallow fermenters might have a positive impact...but a carboy with a piece of foil or even an open bucket?

That Sierra Nevada video is interesting, but it appears they transfer the beer just as the krausen starts to fall. I am not sure why the batch seems to rise and fall a few times...do they add more wort during fermentation?
 

Northern_Brewer

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I am not sure why the batch seems to rise and fall a few times...do they add more wort during fermentation?
I'd imagine that they're rousing, sort of like in a Yorkshire square.

The key thing for open fermentation is a proper top-cropping yeast - something like Brewlab CC is a beast. That provides a lot of your protection from nasties (both physical and oxygen) getting in. Most homebrew strains tend to come from breweries that use conicals and are adapted to that environment.

It does make a difference though with some strains - WLP037 is notoriously phenolic in traditional homebrew setups, but far less so in a homegrown "square".
 

zipfly

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Seems like the point of open fermentation is increased oxygen exposure during fermentation, and bragging rights for having used a "traditional" method.

Oxygen:
I prefer non-oxidized beer, so I wouldn't ever want to do an open fermentation. I don't believe the freezer will be effectively purged, and if it does, then it's not really open fermentation, it's closed fermentation with lots of headspace.

Contamination:
Since you're covering it, contamination risk is probably fairly low. If you want an open fermentation without contamination risk, pump filtered air into the headspace.

Krausen:
I use Foam Control (AKA Fermcap-S), which helps keep krausen under control, along with underpitching and underaerating. Also I ferment in the mid 60s (WLP300). Krausen doesn't grow more than a few inches.
I bottle condition, so there's plenty of yeast in every bottle. Use low calcium water (like 30-40ppm) to minimize flocculation.
My results are fantastic for my taste, better than any commercial hefeweizen I've had except maybe weihenstephaner when I can get it fresh, rarely.
This is one of my favorite styles. I'm getting thirsty just thinking about it.
Cheers.
Lpp
 

cire

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No brewer would desire to make oxidised beer, but some do manage.

There is nothing terrifying about beer and oxygen. I pour and drink mine in an atmosphere with 21% oxygen, just that there are some occasions when contact with it can and will lead to problems.

IMG_20180726_113229954.jpg


The above was taken at a British brewery that is known worldwide and does not make oxidised beer. The FV on the left is, obviously, at maximum krausen (maybe 4 feet deep) and likely in its 3rd day. That on the right was brewed earlier the same day I took the picture and is seen being roused, which happens every 3 hours or so which obviously increases the oxygen in the wort and improves fermentation.

I too open top ferment, but my largest FV is only 20" high (100 litre/~25 US gallon capacity) which with similar Yorkshire yeasts, regularly roused and with temperature control will retain up to ~15 gallons of wort with krausen. If a lid was fitted its capacity would be halved as the yeast would find a way out.

Rousing is stopped when fermentation begins to subside, when the lid is fitted. The yeast in the beer then quickly drops out and the krausen is harvested. My beers are usually casked within 7 days of pitching, when it still contains some yeast and fermentables to ensure any absorbed oxygen is then naturally reduced by the yeast to a few parts per billion.

Potentially, if such a beer were fermented with the same or or other yeast at lower temperature, unroused with lesser krausen to be kept under cover it would likely take another week or more to ferment and then may not retain any active yeast or sugars that would stop the beer retaining any absorbed oxygen.
 

Bassman2003

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Open fermentation is kind of an unknown for homebrewers. This would be a great Xbeeriment. Couple of things I thought about when reading this thread:

1) Oxidation. It seems to me that whole point of open fermentation is to let the active yeast interact with the atmosphere while fermenting which provides more flavors. Hence oxygen is an important part of the process. Remember, any brewery in Germany is going to be naturally carbonating (spunding etc...) which means the "open" fermentation would only last for a short time. The still fermenting beer would be moved out of the fermentation vessel for CO2 capture. Thus protecting it from oxidation.

2) If the OP is having explosive fermentations then you are probably fermenting the beer at too high of a temperature. Aim for pitching at 59f and holding at 62f for the rest of fermentation to keep the yeast a little more controlled. At these temps hefe yeast is not as explosive in my experience.

3) Specific character from a location. Does an open fermentation in Germany create a different tasting beer than an open fermentation in Mongolia? If everything was kept the same outside of location would there be a difference? There seems to be for Belgian beers. Topic for conversation.
 

Bassman2003

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On another note, when I visited the Pilsner Urquel brewery in Pilsn, the old brewery under the ground still was fermenting the famous lager beer in open fermenters. So it is not just for goofy ale types of beer.
IMG_0308.jpg
Picture 095.jpg
Picture 097.jpg
 

CascadesBrewer

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On another note, when I visited the Pilsner Urquel brewery in Pilsn, the old brewery under the ground still was fermenting the famous lager beer in open fermenters. So it is not just for goofy ale types of beer.
It is an interesting picture, but I will go out on a limb and state that Pilsner Urquell ferments in vessels MUCH larger than those wooden casks! I am curious if those are some special limited batch, or something they do just as part of the tour.

I am not anti-open fermentation...just ignorant on the topic.
 

Bassman2003

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This is an interesting part of the brewery. They keep two versions of the brewery going, old and new. The new version is modern and above ground. The old brewery is directly below and naturally cool. They still brew in the old method as a control to make sure the new brew does not wander from the taste. At this point I am sure they know if it wanders or not but it is nice to keep traditions alive. Here is one from the next stage where they give you samples straight from the old wooden huge barrels.

Picture 103.jpg
 

CascadesBrewer

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This is an interesting part of the brewery. They keep two versions of the brewery going, old and new. The new version is modern and above ground. The old brewery is directly below and naturally cool. They still brew in the old method as a control to make sure the new brew does not wander from the taste. At this point I am sure they know if it wanders or not but it is nice to keep traditions alive. Here is one from the next stage where they give you samples straight from the old wooden huge barrels.]
Wow! Great pic. While we are chatting about traditional breweries and open fermentation...

The open fermenters at Cantillon (I was there in July and I think they only brew during the winter months)...

2014-07-23 @07-04-38.jpg



Me hanging out in their barrel aging room...they had a LOT of barrels!
2014-07-23 @07-09-40.jpg
 

RPh_Guy

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I believe the first pic is a coolship, not a fermenter.

I'm jealous; I'd love to go there!
 

Bassman2003

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If I remember, although it looks like a coolship it is where they get their wild yeast to start. I think they can open up the slats at let the air in.
 

RPh_Guy

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You're describing a coolship (koelschip) as it's used for traditional sour brewing. ;)
 
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Vale71

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Open fermentation is kind of an unknown for homebrewers. This would be a great Xbeeriment. Couple of things I thought about when reading this thread:

1) Oxidation. It seems to me that whole point of open fermentation is to let the active yeast interact with the atmosphere while fermenting which provides more flavors. Hence oxygen is an important part of the process. Remember, any brewery in Germany is going to be naturally carbonating (spunding etc...) which means the "open" fermentation would only last for a short time. The still fermenting beer would be moved out of the fermentation vessel for CO2 capture. Thus protecting it from oxidation.
It's already been done by the Brülosophy guy, as usual with zero understanding of what he was actually doing. He basically used two identical kegs as fermenters and put the lid and a blow-off on one and no lid on the other. Needless to say the two resulting beers tested identical, which is what was to be expected.

Open fermentation is actually a misnomer, it's really not about the vessel being "open" as any vessel that vents CO2 immediately and thus mantains ambient pressure is "open", regardless of whether it's completely open or simply vents through a small hole in the top. The only thing that does make a difference is fermenter geometry. Oxygen plays no part in the process, if properly coducted an open fermentation will not lead to oxidation of the beer which would only cause off flavors. The beer must be protected at all times by the kräusen and then transferred in a timely fashion to a closed vessel for carbonation and maturation.
 

CascadesBrewer

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If I remember, although it looks like a coolship it is where they get their wild yeast to start. I think they can open up the slats at let the air in.
Yeah...I am not exactly sure what they ferment in. I did not see anything in my pictures that looked like a fermenter and a Google search did not turn up much other than some barrels overflowing.

This tour video shows a shallow vessel (about 3-4 ft deep) that is in the room next to the open coolship where they might ferment (the guy in the video calls it a coolship). (the time stamp link does not seem to work, but it is at 17:22)

 

Vale71

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Yeah...I am not exactly sure what they ferment in. I did not see anything in my pictures that looked like a fermenter and a Google search did not turn up much other than some barrels overflowing.

This tour video shows a shallow vessel (about 3-4 ft deep) that is in the room next to the open coolship where they might ferment (the guy in the video calls it a coolship). (the time stamp link does not seem to work, but it is at 17:22)
It's a bit too deep to actually be a coolship. It's also partly covered which doesn't make sense for a coolship as it would slow down cooling. That's probably a "primary fermentation vessel" although with spontaneous fermentations the most interesting part of fermentation obviously takes place in the barrels.
 

RPh_Guy

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I am not exactly sure what they ferment in
Barrels!

Once it runs through the coolship it goes into the larger vessel (I'm guessing the larger stainless vessel there that you mentioned) to be mixed together and then it goes into barrels.

In that video they show the coolship at 18:15.

Cheers
 

Bassman2003

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Thanks for posting the video. I did not remember the fermenters that they passed on the way to the coolship!

Vale, if interaction with the atmosphere does not play a part in "open fermentations", would you say that a low profile fermenter design with an airlock right next a low profile fermenter that was open would yield the same results?
 

Vale71

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Vale, if interaction with the atmosphere does not play a part in "open fermentations", would you say that a low profile fermenter design with an airlock right next a low profile fermenter that was open would yield the same results?
Exactly. Many traditional breweries have had to refurbish their "open fermenters" to comply with current healht and safety regulations. They've kept the same geometry but the tanks are now lined with stainless and capped, allowing CO2 to be vented to the outside and protecting the wort from falling debris. Basically the only difference to a modern conical is they cannot withstand any positive pressure and hence don't allow spunding.
 

Bassman2003

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Can I ask how you know this? And do these breweries think the beer turns out the same as before the forced retrofit?
 

cire

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IMG_20170221_114508743.jpg



Handrails and wire mesh would seem sufficient to comply with health and safety regulations at this brewery and forced ventilation removes excess CO2. I would have though beer would not be the only food to be made uncovered. As far as I am aware, this brewery doesn't make lager or use bottom fermenting yeast and has no conical. The picture I posted previously is of a brewery that uses a bottom fermenting yeast to make a lager in a conical, although I've not seen it, only a written hop schedule for that conical.
 

Vale71

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Can I ask how you know this? And do these breweries think the beer turns out the same as before the forced retrofit?
It was part of my training. Commercial breweries don't just think the beer stays the same, they actually test for consistency. Good breweries manage to achieve it too.
 
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Vale71

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This is an interesting part of the brewery. They keep two versions of the brewery going, old and new. The new version is modern and above ground. The old brewery is directly below and naturally cool. They still brew in the old method as a control to make sure the new brew does not wander from the taste. At this point I am sure they know if it wanders or not but it is nice to keep traditions alive. Here is one from the next stage where they give you samples straight from the old wooden huge barrels.

View attachment 626679
There weren't as many barrels (actually just a couple) when I visited but it was high summer so I imagine turnover was at its highest level.
As for the open fermentation and the wooden casks, Urquell makes a sort of "limited edition" beer that is sold unfiltered in small wooden casks and that's only available locally for events. I had a chance to try it at an event in Munich and it tastes more like a homebrewed version of Urquell and less like the commercial version, exactly like the one I got to taste from the huge barrels when I later visited the brewery in Plzen. I guess what you saw down there was production of this limited edition beer. Again, when I visited we didn't get to see that so it's probably a seasonal or otherwise sporadic thing too. The modern brewery (which I gather you visited as well) is all shiny stainless steel now.
 

Bassman2003

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Thanks for your reply. So much to learn about fermentation... I thought I read that open fermentation is the easiest way to harvest yeast from the top cropper's. So maybe that is why the practice hangs around instead of flavor contribution.

Sounds like we were lucky to see the beer production when we visited the brewery.
 
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