Ask The Brewmasters

Could anyone speak to how oxidation and its associated flavor problems are avoided when using open fermentation vessels for primary fermentation? 

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John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
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Open fermenters are so cool!  My first paid brewing gig was at Sudwerk Privatbraueri Hübsch in Davis, CA.  One of my duties was racking beer from open fermentation to lagering, then cropping and sieving yeast, and cleaning the open fermenter by hand.  It's sad that more brewers do not have the chance to work with open fermenters because fermentation is much more spectacular when it can be seen.

When I was at Sudwerk in the early 90's, we typically moved beer when it was about 2º Plato above typical terminal.  During fermentation, carbon dioxide "spills" from the top of fermenter and creates a CO₂ enriched environment above the beer.  Oxygen that diffuses through this layer must first diffuse through the bubbly kräusen and into the beer below, which still is teaming with active yeast.  Suffice to say, fabulous lagers and ales have been produced using similar methods of a very long time.

The key to the oxidation concern likely lies in moving beer out of the open fermenter before the party is over.  My empirical research into the effects of oxygen pick-up during fermentation in open tanks, i.e., beer sensory in brewery taprooms, suggests no correlation between stale-tasting beer and open fermentation!

Sierra Nevada, New Glarus, Russian River, and Prost are examples of US breweries currently using open fermenters for some of their beers.  Up until the recent addition of some CCV capacity, Anchor exclusively used open fermenters and horizontal aging tanks for all lager and ale production.

Cheers!

------------------------------
Ashton Lewis
Manager of Training and Technical Support
BSG Craftbrewing
MBAA District Great Plains, Technical Chair
Springfield, Missouri
(417) 830-2337
------------------------------

Original Message:
Sent: 08-25-2024 17:17
From: John Kochendorfer
Subject: Open Fermentors

Could anyone speak to how oxidation and its associated flavor problems are avoided when using open fermentation vessels for primary fermentation? 

------------------------------
John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
------------------------------

Sorry I'm a little late on this, but thank you to all who responded. 

I have never used open fermentors, but I understand that many well respected breweries past and current have, and continue to use them. I think a lot of my question came from how to deal with the beer at the end of fermentation and transferring to another vessel, and I think the comments about transferring while the fermentation still has a little life in it is probably critical and makes sense. It seems obvious now that I think about it, but I was raised in a Cylindro-conical world.

Hopefully it's something I get to experiment with someday.

Thanks

------------------------------
John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
------------------------------

Original Message:
Sent: 08-26-2024 12:57
From: Ashton Lewis
Subject: Open Fermentors

Open fermenters are so cool!  My first paid brewing gig was at Sudwerk Privatbraueri Hübsch in Davis, CA.  One of my duties was racking beer from open fermentation to lagering, then cropping and sieving yeast, and cleaning the open fermenter by hand.  It's sad that more brewers do not have the chance to work with open fermenters because fermentation is much more spectacular when it can be seen.

When I was at Sudwerk in the early 90's, we typically moved beer when it was about 2º Plato above typical terminal.  During fermentation, carbon dioxide "spills" from the top of fermenter and creates a CO₂ enriched environment above the beer.  Oxygen that diffuses through this layer must first diffuse through the bubbly kräusen and into the beer below, which still is teaming with active yeast.  Suffice to say, fabulous lagers and ales have been produced using similar methods of a very long time.

The key to the oxidation concern likely lies in moving beer out of the open fermenter before the party is over.  My empirical research into the effects of oxygen pick-up during fermentation in open tanks, i.e., beer sensory in brewery taprooms, suggests no correlation between stale-tasting beer and open fermentation!

Sierra Nevada, New Glarus, Russian River, and Prost are examples of US breweries currently using open fermenters for some of their beers.  Up until the recent addition of some CCV capacity, Anchor exclusively used open fermenters and horizontal aging tanks for all lager and ale production.

Cheers!

------------------------------
Ashton Lewis
Manager of Training and Technical Support
BSG Craftbrewing
MBAA District Great Plains, Technical Chair
Springfield, Missouri
(417) 830-2337

Original Message:
Sent: 08-25-2024 17:17
From: John Kochendorfer
Subject: Open Fermentors

Could anyone speak to how oxidation and its associated flavor problems are avoided when using open fermentation vessels for primary fermentation? 

------------------------------
John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
------------------------------

All the modern breweries I know that use open fermenters would transfer beer into closed fermenters before krausen crashes. I think one of the reasons is avoiding oxidation, the other is that fermenting in an open vessel can not really benefit beer after krausen stage. Those traditional breweries that leave beer in open fermenters longer should theoretically still have a layer of CO2 to protect beer but there could be more reasons and purples beyond that. 

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Asher Sun
Brewer
Pfriem Family Brewers
Hood River OR
------------------------------

Original Message:
Sent: 08-25-2024 17:17
From: John Kochendorfer
Subject: Open Fermentors

Could anyone speak to how oxidation and its associated flavor problems are avoided when using open fermentation vessels for primary fermentation? 

------------------------------
John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
------------------------------

Lets look at the process of fermentation and just touch on the basics of CO2 production and the fact that it is heavier than air and Krausen / Foam makes  wonderful layers of protection from dust and oxygen . Hence no oxidation or infections from debris 

Thanks 

WSP

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W. Scott Pyatt
Consultant
Founder /Former COO Catawba Brewing Co / Palmetto Brewing Co
Glen Alpine NC
(828) 527-8097
------------------------------

Original Message:
Sent: 08-25-2024 17:17
From: John Kochendorfer
Subject: Open Fermentors

Could anyone speak to how oxidation and its associated flavor problems are avoided when using open fermentation vessels for primary fermentation? 

------------------------------
John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
------------------------------

Hi John,

Some random thoughts on Open Fermentation:

Certainly, beautiful beers are made in Unitanks, but open fermentation, for me at least, is wonderful to have in your too belt.

We use open fermenters to benefit some brands. Great for skimming top fermenting yeast or skimming harsh hop drive/brandhefe off highly hopped Pils, for example.

There's no concern with oxidation as the beer is only in open tanks during primary. Yeast activity keeps the beer in a reduced state. Similar to wort aerate.

As long as the open fermenters are not placed near malt dust generation and the like, contamination is also not a concern in a clean brewery. Any bad experience I've had with microbes are from biofilms that develop in hidden dark spaces in tanks, pipes and fillers.

Benefits of Open Fermentation?

Old time brewers lament modern practices - brewing in closed systems via computer without the touch of the brewer. When I was a apprentices, the old brewmaster knew exactly when it was time for me to move beer to the lager cellar without needing a microscope or spindle – he simply blew on the Kräusen, if the ferment did not immediately cover the open spot and if the beer under the foam was brown not milky white, he knew the cell count and gravity were right for move to the Lager Cellar.

One gains advantage, for example, by observing open fermenter appearance and aroma. This is lost in Unitanks. 

Skimming benefits bitterness quality. 

Top cropping yeast can yield superior quality. You often hear UK brewers brag about the many thousands of generations they get out of their yeast. This is because they top crop beautiful, heathy yeast – some ale or Weiss yeast do not respond well to cone harvest thus require frequent repropagation.

Of course, gains in flavor harmony and yeast quality come at a cost - increased labor and CIP expense. Plus, you have to be ready to move to lager cellar when the beer demands. And collection of CO2 is difficult.

By the way, about esters. Esters are volatile and when fermentation is vigorous, as in a tall CCT, much of the esters are scrubbed with vigorous CO2 evolution. A shallow tank, whether open or closed, has less severe convection so more esters are retained.

Happy Brewing,

Daniel Carey

New Glarus Brewing Company

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Daniel Carey
Brewmaster
New Glarus Brewing Company
New Glarus WI
(608) 527-5850
------------------------------

Original Message:
Sent: 08-25-2024 17:17
From: John Kochendorfer
Subject: Open Fermentors

Could anyone speak to how oxidation and its associated flavor problems are avoided when using open fermentation vessels for primary fermentation? 

------------------------------
John Kochendorfer
Head Brewer
District Brewing Company
Mount Vernon WA
------------------------------