Open fermentation experiment

[FoodScienceBrewer]

I would like to know what you all think about a small open fermentation I am attempting with this Hefeweizen I brewed yesterday.

I ended up with around 4 gallons and put the bulk of it in my plastic 5 gallon bucket fermentor with an airlock. This jar has no airlock and a ziplock bag over the top (not airtight) to prevent dust/flies from entering.

I’m curious if anyone has any predictions for how the two batches will differ (if at all). I am aware that reduced pressure on the yeast can allow a faster fermentation as well as producing more aroma/flavor compounds (banana and clove). I’m also aware the surface area of typical open fermentors is larger to allow more undesired compounds to leave. This is all I had to work with. I could remove the lid entirely but I am worried about contaminants. Any and all advice welcome

 

[VikeMan]

I ended up with around 4 gallons and put the bulk of it in my plastic 5 gallon bucket fermentor with an airlock. This jar has no airlock and a ziplock bag over the top (not airtight) to prevent dust/flies from entering.

I’m curious if anyone has any predictions for how the two batches will differ (if at all). I am aware that reduced pressure on the yeast can allow a faster fermentation as well as producing more aroma/flavor compounds (banana and clove).

While pressure does affect yeast, I doubt the lack of an airlock here will make much difference in that regard. A physicist on another forum computed the pressure added by the liquid in a standard 3-piece airlock at about 1/400th (not a typo) of an atmosphere, which is much smaller than natural fluctuations in atmospheric pressure.

 

[AlexKay]

Right, the total pressure is the same. The real difference here is from gas mixing; the airlock keeps CO2 in and air out. So an open fermentation gives you a much lower partial pressure of CO2 — with complete mixing, practically none, really, versus 1 atm for an airlock. The CO2 in solution is correspondingly much lower, which also raises the pH, and those are things yeast absolutely care about.

Folks doing “pressure fermentation” with a spunding valve are seeing differences for exactly the same reason: more than an atmosphere of CO2, more CO2 in solution, lower pH.

Actual effects of pressure only kick in when you have industry-scale cylindroconicals.

 

[Franktalk]

If you want the gases to mix, take the plastic bag and the lid off of your fermenter. You have a healthy Krausen, so nothing will infect the beer. The idea is to give the yeast plenty of air and oxygen, so it can express itself.

Don't worry too much about your batch getting infected. As long the space where you ferment is relatively clean and consistent, it will be fine. I do open ferments all the time with top-cropping yeasts and haven't gotten an infection yet. Keep it covered loosely until the krausen forms, and then open it up all the way and leave it until the it begins to drop. You will be glad because you'll end up with a nice beer with plenty of yeast expression.

 

[FoodScienceBrewer]

Thanks for the replies. I woke up this morning to what I believe is high krausen so I decided to go with the advice of removing the lid. I will keep the lid off until I notice a significant drop. After that I will put the airlock on.

Hopefully I won’t get any foam over but if I do it shouldn’t be a big deal

 

[Miraculix]

You want to cover it with a thin cloth to keep fruit flies out. They can ruin batches. Otherwise, cool experiment.

 

[FoodScienceBrewer]

Actual effects of pressure only kick in when you have industry-scale cylindroconicals.

When you say this do you mean much larger tanks will build a significant amount of pressure (enough to affect the yeast) even with an open spunding valve?

 

[FoodScienceBrewer]

You want to cover it with a thin cloth to keep fruit flies out. They can ruin batches. Otherwise, cool experiment.

Good call. I will when I get back from class in an hour. Hopefully none already got in there.

 

[VikeMan]

When you say this do you mean much larger tanks will build a significant amount of pressure (enough to affect the yeast) even with an open spunding valve?

Don't take my word for this, but from memory, fermenter height adds about 1 PSI for each 3 feet, due to hydrostatic pressure.

 

[FoodScienceBrewer]

Don't take my word for this, but from memory, fermenter height adds about 1 PSI for each 3 feet, due to hydrostatic pressure.

Oh I see. That’s for sure another reason why industry open fermentors are so short and wide. I thought you meant the pressure created by fermentation. The head brewer where I worked mentioned the affect of the gaseous pressure being lowered but he had been wrong about things before.

 

[HighVoltageMan!]

The issue with pressure is often cited as a problem or concern for yeast. Yeast are quite robust and can withstand a great deal of pressure and remain healthy. The biggest thing that effects yeast under pressure is dissolved co2. As pressure increases and temperature is lowered more dissolved co2 that remains in solution. It is well established that in general, dissolved co2 will inhibit ester production and reduce yeast growth. So while pressure does effect yeast metabolism, it does it indirectly.

Open fermenters are often shallow and have a large surface area, this allows for co2 to be more readily removed from the vessel. It is possible to mimic the conditions of an open fermenter and keeping the vessel "sealed" with an airlock by decreasing the depth of the fermenter and increasing the surface area of the beer. An example would be a using a stubby 1/4 barrel Sanke to ferment 4-5 gallons.

 

[Beermeister32]

Back in the 1960's Dad would ferment his illegal beer in a 15 gallon crock with a towel over the top. I guess you would have called it open fermentation. The smell was fantastic!

 

[youngson616]

Cool experiment I hope it comes out well! Yes I agree with some to leave the bag off but loosely cover with something to avoid contaminants like flies. I will be doing my first open fermentation this weekend in a bottling bucket with the lid off inside my deep freezer, maybe cracked open not sure yet. Im hoping to easily transfer the beer after 3 or so days of fermenting to a carboy with the bottle bucket setup to finish fermentation in a closed environment.

 

[Miraculix]

I did an open fermented saison recently with a strain prone to have a saison stall. It didn't stall at all and went straight to fg in a few days. Taste was also great.

You just have to manage the brew correctly, you really want to airlock the brew before fermentation finishes.

 

[jerrylotto]

You should keep it in a space that has minimal air movement. A closed room or closet is ideal without active ventilation.

 

[McMullan]

How much pressure an airlock adds depends on the airlock used, not necessarily what a physicist on another forum reckons. Yes, yeast can tolerate pretty high pressures. Mainly because they have a remarkably strong cell wall to stop the cell getting too distorted or even bursting. However, it only takes a little pressure to alter yeast behaviour. What you can do, as an interesting experiment, is ferment ale using a characterful English yeast strain open vs under a few psi, same batch of yeast at the same pitching rate and temperature. Does it make a difference? I think so. Is there a reason why many of the finest breweries in England ferment open? I'd say open fermentations have generally worked better for me, in terms of fermentation performance and the end product.

 

[McMullan]

The issue with pressure is often cited as a problem or concern for yeast. Yeast are quite robust and can withstand a great deal of pressure and remain healthy. The biggest thing that effects yeast under pressure is dissolved co2. As pressure increases and temperature is lowered more dissolved co2 that remains in solution. It is well established that in general, dissolved co2 will inhibit ester production and reduce yeast growth. So while pressure does effect yeast metabolism, it does it indirectly.

Yes, CO2, as a stress factor, affects
yeast metabolism, but I think you've underestimated the potential impact of pressure. At higher pressures the cell membranes, proteins, including enzymes, etc., become distorted. Some more than others. This affects yeast metabolism directly, even when fermentation appears unaffected the end product can be very different.

 

[VikeMan]

How much pressure an airlock adds depends on the airlock used, not necessarily what a physicist on another forum reckons.

Perhaps you could show us the math then, with airlocks other than the standard three piece airlock mentioned. Maybe with a variety of fluids and fill levels.

 

[Somesaymybeerisdrinkable]

Don't take my word for this, but from memory, fermenter height adds about 1 PSI for each 3 feet, due to hydrostatic pressure.

I am also working off memory here, but I believe 1 atmosphere is equal to about 33 feet of water or 14.7PSI. (33 feet)/(14.7 PSI) = 2.25 ft/PSI. Wort would be slightly different because it weighs more than water

On a different note if these slight differences in atmospheric pressure change the taste then beer fermented in Denver should have a perceptible difference compared to beer fermented in San Diego assuming all other things are equal. I have no means of testing this but it might be an interesting experiment.

 

[hottpeper13]

Sooo, when the Kveik blows all the liquid out of an "S" lock,is it now an open fermentation?

 

[McMullan]

Perhaps you could show us the math then, with airlocks other than the standard three piece airlock mentioned. Maybe with a variety of fluids and fill levels.

I've got Better Bottle dry airlocks that have a tiny glass bead a gnat's fart could move and some big chunky Speidel airlocks that take a relatively large volume of liquid to fill as far as airlocks go, which a gnat's fart isn't ever going to move.

 

[Beermeister32]

On a different note if these slight differences in atmospheric pressure change the taste then beer fermented in Denver should have a perceptible difference compared to beer fermented in San Diego assuming all other things are equal. I have no means of testing this but it might be an interesting experiment.

Charlie Bamforth has some webcasts which discuss this very subject. Important for brewing companies producing same beer at different elevations. Who’d a guessed…

 

[scrap iron]

Back in the 1960's Dad would ferment his illegal beer in a 15 gallon crock with a towel over the top. I guess you would have called it open fermentation. The smell was fantastic!View attachment 780294

My great-grandfather immigrated from Belgium during WWI. I remember the stories as a child him fermenting in crock with a cheesecloth set on top. It was illegal back then too and he stored bottles in a dugout cellar under the kitchen floor. He would pull up a few floorboards to access the cellar.

 

[Beermeister32]

My Grandfather (Dad’s Dad) also made booze. Not sure what he was doing back in those cold North Dakota winters, but Dad had a story about Grandpa’s indoor hooch making back in the 1940’s where he had some sort of alcohol (or propane I suspect) related flash fire that lit all the combustibles in the house. They had one heck of a time getting all the little fires put out.

 

[SFC Rudy]

I ferment my Hefe Weizens in a 15-gallon sterilite container I got from Wal Mart. I use Lallemand Munich Classic dry yeast and that is the closest I have gotten to most of the Hefe Weizens I drank when I was staioned in Germany.

 

[VikeMan]

I ferment my Hefe Weizens in a 15-gallon sterilite container I got from Wal Mart. I use Lallemand Munich Classic dry yeast and that is the closest I have gotten to most of the Hefe Weizens I drank when I was staioned in Germany.

That's interesting. The black industrial tote w/red handles or something else?

How/when do you cover it? Does the shape result in a lot of beer being left behind when racking?

 

[HighVoltageMan!]

Yes, CO2, as a stress factor, affects
yeast metabolism, but I think you've underestimated the potential impact of pressure. At higher pressures the cell membranes, proteins, including enzymes, etc., become distorted. Some more than others. This affects yeast metabolism directly, even when fermentation appears unaffected the end product can be very different.

Below 15 PSI the main reason yeast change their metabolism is due to the presence of co2. This a common means of increasing or decreasing the production of esters. Open fermenters produce beers with higher esters because the co2 is driven off more effectively due to the shallow vessel with a large surface area. Tall conical fermenters produce higher hydrostatic pressure, increasing the amount dissolved co2 and with a smaller surface area to depth ratio, co2 will remain in solution. Weihenstephan produces lagers in fermenters reported to be +50 meters tall. Their wheat beer is fermenter in large shallow horizontal fermenters. The stated reason was to control ester production.

It's commonly known that co2 directly affects ester production but it is not completely understood why this takes place. It's also commonly known that if the yeast is exposed to moderate pressure, 1 atmosphere or lower, it will not significantly impact the yeast directly. I've heard Bamforth speak about this on a number of occasions. In all my research on this subject, the only ones who claim the pressure is the main reason for the lower levels of esters are mostly homebrewers.

 

[SFC Rudy]

That's interesting. The black industrial tote w/red handles or something else?

How/when do you cover it? Does the shape result in a lot of beer being left behind when racking?

I use the clear one with the white lid Robot or human?. The lid does not seal allowing the CO2 to escape. I drilled a hole for a spigot on one end and tip it when almost empty, maybe one beer left behind.

I ferment on a bench (it's too big for my fermentation chamber. For temp control I use a blichman cooling coil hooked up to my jerry rigged cooler (a pond pump in a bucket of water in my fermentation chamber) Works like a charm.

 

[McMullan]

Below 15 PSI the main reason yeast change their metabolism is due to the presence of co2. This a common means of increasing or decreasing the production of esters. Open fermenters produce beers with higher esters because the co2 is driven off more effectively due to the shallow vessel with a large surface area. Tall conical fermenters produce higher hydrostatic pressure, increasing the amount dissolved co2 and with a smaller surface area to depth ratio, co2 will remain in solution. Weihenstephan produces lagers in fermenters reported to be +50 meters tall. Their wheat beer is fermenter in large shallow horizontal fermenters. The stated reason was to control ester production.

It's commonly known that co2 directly affects ester production but it is not completely understood why this takes place. It's also commonly known that if the yeast is exposed to moderate pressure, 1 atmosphere or lower, it will not significantly impact the yeast directly. I've heard Bamforth speak about this on a number of occasions. In all my research on this subject, the only ones who claim the pressure is the main reason for the lower levels of esters are mostly homebrewers.

In a brewery fermentation CO2 production and sometimes CO2 pressure is inevitable. How are you going to determine what CO2 vs pressure effect? I know an English ale fermented under pressure as low as 5 psi is a very bland affair compared with its equivalent fermented open. I wonder what effect periodic N2 pressure has on yeast in an open fermentation?

 

[HighVoltageMan!]

In a brewery fermentation CO2 production and sometimes CO2 pressure is inevitable. How are you going to determine what CO2 vs pressure effect? I know an English ale fermented under pressure as low as 5 psi is a very bland affair compared with its equivalent fermented open. I wonder what effect periodic N2 pressure has on yeast in an open fermentation?

I’m not sure I understand the question. Every fermentation creates a certain level of dissolved co2. Vessel shape, size, depth all contribute to this level.the only real way to know the level would be to measure it. As far as pressurizing with nitrogen, I guess the effect would be the same. As the liquid is compress, it increases the capacity to absorb co2.

I often wondered if the fermentation could be pressurized without the elevated levels of co2, would there be any similar effects.

 

[pocketmon]

In a brewery fermentation CO2 production and sometimes CO2 pressure is inevitable. How are you going to determine what CO2 vs pressure effect? I know an English ale fermented under pressure as low as 5 psi is a very bland affair compared with its equivalent fermented open. I wonder what effect periodic N2 pressure has on yeast in an open fermentation?

THE BRÜ LAB podcast Episode 041 | Pressurized Fermentation w/ Dr. Andrew Macintosh might answer your question.

 

[bracconiere]

beer fermented in Denver should have a perceptible difference compared to beer fermented in San Diego

well coors says that all the time!

 

[McMullan]

@HighVoltageMan!, I'm still not convinced CO2 is the primary driver. There are several factors, including other stress factors, that reduce biomass production during fermentation to affect ester profiles. In my open (Yorkshire square) fermentations I control esters by repitching freshly cropped yeast relatively cool (17°C) at high pitching rate. Admittedly, recirculating the actively fermenting wort periodically knocks out CO2. if I pitch at a low rate to promote biomass production esters get a bit overwhelming in a poorly balanced beer.

@pocketmon, that was interesting, thanks. I'm going to read the publications to get a better idea about the experimental designs and their research. From what I could tell so far it sounds like pressure itself might be a confounding variable. Obviously, very difficult to tease apart the effects of CO2 vs pressure in a brewery fermentation. What we do know is under relatively unreactive N2 pressure the yeast gene expression profile changes.

 

[Oleson M.D.]

Pilsner Urquell still does open fermentation today.
Here are couple photos from their brewery, taken when we did a tour:

 

[McMullan]

Right, they haven't published much and, after listening to another podcast, I'm here: interesting theory to explain a correlation. Looking forward to some actual science to test and confirm what's being proposed.

Disclaimer: insufficient data to fact-check.

 

[McMullan]

I found this interesting, and, better still, it's publicly accessible. I'm thinking of messing around with a weak vacuum in yeast starters, although it's not clear if it increases biomass - I suspect it doesn't - it appears to keep more yeast cells in suspension, where we want them. The proposed benefits for fermentation are more for commercial brewers, I imagine. Pay attention to the methods and results for yeast propagation. They used dry Diamond Lager yeast. Their findings confirm what I've observed with dry yeast. Viability <50% and best propagated before pitching, preferably repitched, imo, to get them conditioned properly. I'm not sure why their wort gravity range was so narrow. Bit of a missed opportunity, like not measuring total biomass, before and after.

Here's the other podcast:

https://www.masterbrewerspodcast.com/230
If anyone has a copy of the MBAA article I could 'borrow' that would be very nice.

 

[FoodScienceBrewer]

Update: I put the airlock on the open fermentation vessel on Friday after observing consistent gravities over 2 days in the main bucket. I've been monitoring the gravity of the main (I tasted those samples and they are incredibly delicious. Banana, clove, and no off flavors. Exactly what I would expect from a Hefeweizen) which makes me excited to try the open fermented version. I have more bottles and caps arriving on Wednesday and I plan to bottle as soon as they arrive. If anyone is interested I will post tasting notes from the main batch vs the open fermented batch.

 

[Miraculix]

Update: I put the airlock on the open fermentation vessel on Friday after observing consistent gravities over 2 days in the main bucket. I've been monitoring the gravity of the main (I tasted those samples and they are incredibly delicious. Banana, clove, and no off flavors. Exactly what I would expect from a Hefeweizen) which makes me excited to try the open fermented version. I have more bottles and caps arriving on Wednesday and I plan to bottle as soon as they arrive. If anyone is interested I will post tasting notes from the main batch vs the open fermented batch.

That is too late, you will have already oxidised the batch. The trick is to airlock it before fermentation finishes.

 

[jambop]

Air lock shamare lock! Take a look here www.samuelsmithsbrewery.co.uk/ this is how proper beer has been made for centuries !

edit
I notice you are making a wheat beer... Again this style of beer has been made for centuries using open fermenting vats . As a very experienced brewer has told me there are very few air borne infections that can do much to a wort that has been supplied with adequate active yeast starter .

 

[CascadesBrewer]

Air lock shamare lock! Take a look here www.samuelsmithsbrewery.co.uk/ this is how proper beer has been made for centuries !

Note that the picture of open fermenters also shows a very active krausen. Once fermentation starts to slow, breweries will transfer the beer into a closed fermenter (well, centuries ago they may have transferred into a wooden vessel and the beer had some level of oxidation and sour character).