Questions about open fermentation

Hey everyone, I’ve heard of people using open fermentation for certain styles, but I’ve been learning that people are also using it for their regular “clean” ales, as well. I just read the Brewing With Wheat book and found that breweries use open fermentation for things like Hefeweizen. So now this has me wondering…

  1. Is there cause for much concern of infection?
  2. How long should you wait to close it up?
  3. What are the pros/cons?
  4. Is there some good literature to read up on regarding open fermentation?
  5. Anything you’d like to add or point out?

Thanks in advance.

Open fermentation is practiced more than I used to think. In the US I have seen it at breweries such as Anchor, Sierra Nevada, and breweries/brewpubs with the Pugsley/Austin type systems. Many German breweries use open fermentation for their Hefeweizen. Some also use it for their lagers, from smaller breweries to larger ones like Schrönram.

  1. The fermenters are in a clean room. Some might be filtering the air to remove airborn microbes.

  2. When the krauesen starts to drop.

  3. More esters with open fermentation. CO2 is dissipated over the Krauesen. The Braunhefe (dark stuff at the top) can be skimmed.

  4. Don’t know.

  5. I have done open fermentation on ales. In a bucket the lid is not snapped down. On my conical I have the lid spaced up a little with some metal rods. In a carboy use AL foil over the neck opening.

This is always fun to watch. Bigfoot fermentation.

Now that is cool!

Jeff, IIRC you’ve been to Ayinger, do they do open fermentation?

Some yeasts really benefit from open fermentation.  Some yeasts need more oxygen than can be absorbed by wort to be healthy, particularly some English yeast strains, which were traditionally open fermented.  Some yeasts are thought to be sensitive to high CO2 levels particularly DuPont saison yeasts.

Big beers can benefit from open fermentation.  Some people prefer closed fermentations and do a second injection of oxygen instead about 12-24 hours after pitching instead.

AFAIK, no one has yet determined whether Dupont yeast is sensitive to pressure or CO2.  At any rate, it does like to be open fermented.

The Hefeweizen are open. It looked like the lagers are closed in conicals, but I didn’t see the tops.

Many of the bigger German breweries use closed conicals. You can find them visible on Google maps.

The Weizens at New Glarus have their own room and I believe he was trained in Germany.

He apprenticed at Ayinger.

I haven’t been through that many British breweries, bu many are said to open.

Young’s Ram Brewery was open in big rectangular fermenters. RIP.

Fullers is closed conicals.

The Jennings Brewery had loose fitting hoods, with loose fitting doors. I think the hoods were to keep things from floating in.