Open Fermenters

jacksonbrown

Who uses them and why?

I guess most of us started out brewing normal beers so it was air locks all the way but is it really necessary.
Lambics etc ferment open and so do a lot of wines.
Quite a few whiskeys do too, Woodfords Reserve comes to mind but my understanding is it was the norm back in the day.
How does it effect consistency, quality and yield vs running CO2 top pressure?
Obviously the savings in set up cost are appealing but CIP gets a bit tricky.

So whats the whole story?

Kapea

I use "open" fermentors for fruit ferments. They are not truly open. They are 10 gallon SS Volrath stock pots that I no longer use as wort kettles. I lay a loose fitting lid on them during fermentation. That makes it easy to punch down the cap. And saves an explosive buildup of carbon dioxide pressure from forming when a piece of fruit plugs up the airlock.

There is a saying amongst my homebrewing friends, "You're not a true homebrewer if you've never mopped the ceiling!"

A friend of mine used to brew professionally for Shipyard Brewery in Orlando. They were very tradional English style ales fermented in open top fermenters. If you pitch enough fresh yeast wild things won't have a chance to get started before the yeast takes over. Yeast are very territorial critters. They don't tollerate illegal aliens movin' into da hood. Due to the density of carbon dioxide, a carbon dioxide "blanket" forms over the ferment, preventing oxidation. The fermented beer was transfered to bright tanks for clearing, and then on to service tanks for the bar, or into kegs for offsite sales. Some was set aside to be served in the bar as cask condition ale via their beer engine.

CIP was a pump up sprayer, a long handled scrub brush and a trigger spray nozzle on a garden hose.

grim

Open.

Initially with flip-top bulk dairy tanks, now with 550g Custom Metalcraft open top fermenters. Open top fermentation isn't only common in American whiskey, but for many years was the standard for Scotch as well. There are still many distilleries in Scotland using open wooden wash backs. Closed vs. open meaning airtight or not, not whether it has a lid or covering.

One factor you need to consider is the duration of fermentation, which in many of large scale commercial open-top shops is around 2-4 days (grain), which is very very different from the kinds of timescales that are looked at as acceptable on the hobby side.

Open top is also common on the red wine side as well.

jacksonbrown

Exactly my point. I'm just wondering about the reasons.
It was a long time ago when I did my initial reading but am I right in thinking that the yeast have an aerobic, then an anaerobic cycle. First they work of the available oxygen by multiplying, then when that is depleted they switch to anaerobic and the result is ethanol production?
The other benefit of a slight positive pressure in the fermentor is that an infection can't get in.
For both these reasons I'm thinking that an air lock is better for consistency and yield.
So why use an open wooden vat?
I'm sure lower outlay and nostalgia/marketing are paying a big part in it but there must be more to the story?

grim

You've been lied to by the brewing community.

The Crabtree effect will largely inhibit respiration in Saccharomyces, which will very happily ferment in the presence of oxygen.

grim

Ok maybe "lied" is a little too harsh. How about, the brewing community largely oversimplified the respiration and fermentation processes, which lead to widespread belief that yeast only fermented in anerobic conditions, and produced biomass during aerobic conditions (respiration, Pasteur effect, etc). Wherein reality, respiration is largely repressed by high glucose and sugar content in the wort.

jacksonbrown

@grim said: You've been lied to by the brewing community.

The more I learn the more I realise how simplified or flawed the 'common knowledge' is.
It's very hard to get the whole picture when most aren't really sure why they do it 'that' way or 'this'.

Someone told me a good story about a roast chicken recipe that had been handed down for generations that involved first splitting the chicken in half.
One day the family were all together cooking lunch and the granddaughter asked her mother why do we cut it in half first.
The mom said 'That's the way we've always done it. I learnt it from your grandmother and you learnt it from me'.
Then thinks for a bit and asks the grandmother who was sitting at the dinning room table drinking a glass off wine.
The grandmother explains that at her house she only has one baking pan and a whole chicken wont fit in it.

@grim said: The Crabtree effect will largely inhibit respiration in Saccharomyces, which will very happily ferment in the presence of oxygen.

Fantastic, exactly the sort of info I was after. Cheers.

grim

Yeah, the epiphany for me was when I finally realized that aerobic and anaerobic were describing the oxygen use of the process, and not the oxygen content of the environment. Secondary to this, that both anerobic and aerobic processes could take place simultaneously.

Now when you put that into the context of how yeast evolved in the real world - it starts to make much more sense. Where exactly would yeast be finding an anerobic environment in the wild? There certainly weren't herds of closed conical fermenters roaming the wild 50,000 years ago. Instead, happily living on ripe and rotting fruit, floating around the neighborhood looking for more.

jacksonbrown

:)) Fare point. I guess CO2 being heavy it could have a protective blanket on a hard fermenting open vat but it the real world?? perhaps drupes acting like sealed fermenters? Clutching at straws?

grim

Actually the opposite, the ability to ferment in an aerobic environment (which is not typical, worth noting) - gave certain yeast species like Saccaromyces a competitive advantage over other micro-organisms (including some yeasts) which strictly follow the Pasteur effect, and cannot - which likely evolved in conjunction with fruit a couple hundred million years ago.

grim

Thank goodness for that, by the way. Where would we be if they didn't?

mark85

Lots of beers in Yorkshire are Brewed in open top "Yorkshire squares". They are as wide as they are tall and were made out of sheets of slate which is really quite porous (and as the name suggests are square shaped). Iv stood over them in Theakstons and Black Sheep and they seem to be protected by strong fast fermentations that get moved to conditioning tanks fairly quickly after they are done.

TheMechWarrior

Ferment for 3 days then lid off and encourage "contamination" by local wild yeast species. Looking for some more esters.

Kapea

Subsequent to the anaerobic yeast fermentation stage can be the aerobic acidification stage by acetobacters, where alcohol is converted to vinegar, hence the clarifying of beer in closed bright tanks.

Kapea

I make honey vinegar (on purpose).

Kapea

@jacksonbrown said: Exactly my point. I'm just wondering about the reasons.
It was a long time ago when I did my initial reading but am I right in thinking that the yeast have an aerobic, then an anaerobic cycle. First they work of the available oxygen by multiplying, then when that is depleted they switch to anaerobic and the result is ethanol production?
The other benefit of a slight positive pressure in the fermentor is that an infection can't get in.
For both these reasons I'm thinking that an air lock is better for consistency and yield.
So why use an open wooden vat?
I'm sure lower outlay and nostalgia/marketing are paying a big part in it but there must be more to the story?

Access to punch down the cap. Anything fermented on solids needs to have this done at least daily.

grim

Or drive the beer guys nuts and run an agitator on a timer in your fermenters. Heads... Exploding...

Kapea

Or fermentors exploding, at least...

rossco

My family are Ukrainian we ferment in open top vats, they have been doing this for at least 3 generations that I know for sure (well over a century). The idea of an airlock is alien to them WTF? Great for rum, leave it for weeks after it has finished. It makes checking the FG easy and more accurate. Float the hydrometer in the wash. I just airlock UJ because it is a more permanent situation.

grim

Yeah that's a major difference - you don't leave an open top ferment sitting around for a couple of days.

zzyzx

@grim said: One factor you need to consider is the duration of fermentation, which in many of large scale commercial open-top shops is around 2-4 days (grain), which is very very different from the kinds of timescales that are looked at as acceptable on the hobby side.

So how on God's good green Earth do they get a ferment in 2-4 days? I'd sure like to dupe that feat...

Since I started home brewing, I've used both open and closed fermenters. All for ales and vodka, partial grain and plain ol' sugar washes. And never had a problem - or even noticed a difference - between them. But they've ALWAYS taken longer than a couple of days. More like a couple of weeks!

What's the secret?

Johnboy

My 60L rum washes will finish in 48 hrs regularly

rossco

@grim said: Yeah that's a major difference - you don't leave an open top ferment sitting around for a couple of days.

I do this often. Once a wash is properly fermented the ABV prevents anything else getting a foothold. The exception would be UJ because it is a living thing, and all grain washes because of the relatively low ABV.

grim

I would imagine the most common risk is fruit flies and acetobacter - losing to ethanol to that vinegar that @kapea is talking about, which means increased volatile acidity in the wash, and increased ethyl acetate in the distillate.

grim

There are also strains of lactic acid bacteria that are associated with late stage fermentation (or what would really be post-fermentation). However, this may be exactly what you are looking for, certain LAB may be generally positive in grain spirits. However the acetobacter will make for a wicked wide heads cut.

Evolution of the Lactic Acid Bacterial Community during Malt Whisky Fermentation: a Polyphasic Study

punkin

My wash fermenters had a hole drilled in the lid with a bottle top over it to keep bugs out. I could leave ujsm for months,not first generation but after it sours on the second it's safe. Its a combination of the abv and the ferment i believe.