Open fermentation in a plastic DIY Coolship

[mcbethenstein]

Over the last 3 years I have been perfecting my Hefe. It's good, but not where I want it to be. I've run experiments on pitching rate, fermentation temperature, open vs closed fermentation, yeast trials, and malt comparisons. I've tweaked it from something good to something great... But it's still not 100% awesome yet. It still has a bit to go to being like the German imports. Don't get me wrong, my beer is GOOD and comparable to many of our local brewpubs in quality, but still not yet like an imported ayinger or franzisksner.

During my yeast trial I got the closest I've ever been to what we are looking for. I fermented 4 - 1 gallon batches each with a different yeast.
In subsequent batches, I have yet to be able to scale up the best batch and get the same results. Accounting for all the other variables I come up with 2 things that could make or break my quest. 1.) during the yeast trial I bottled. I love kegging, but I think it's hurting my Hefe. 2.) my fermenters for that batch were short and fat 1 gallon glass cookie jars. The wort was 5 inches deep at most.

So, re-reading my notes and going over my highlighted passages in "Brewing with Wheat" has lead me to examine my fermenter shape. Open fermentation is awesome, but the levels of cloveiness just aren't there for me yet (I usually use a 7 gal bucket with the cover cracked and a filter bag over it to keep out the nasties). This chart finally hit me, as perhaps the last step that I need to take to bring my Hefe to "world class German Hefe" level, is to look at my fermenter shape.

So after a bit of research on coolships, and using plastic (I have a 4 yr old in daycare... I have no extra cash). I figured out that sterilite containers are indeed food safe. I got a 13.5 gal air/liquid resistant bin at target and went to work transforming it into a fermenter. I drilled 2 holes, one on the lid for an airlock and bung, and one on the side for my bottling spigot. I carefully considered that siphoning from a wide and shallow container like this would be trouble. In hindsight I would lower the height of the spigot, but I have a 90° PVC elbow that fits on the spigot and lowers the fluid intake to hopefully right above the trub.



This first photo shows a saison in full hop drive in my makeshift coolship. I pitched last night at 11 pm, and this was noon today. It was wrapped in clean towels and sheets to keep it warm in my cool basement and shield it from light. The beauty of the coolship is easy access to skimming off that hop drive. The next photo shows after skimming and stirring the yeast back in.
With that amount of headspace the yeasties are pretty happily feeding on oxygen for now. I left the cover offset by an inch, and covered it back up with a clean sheet. After the bulk of fermentation is complete, I'll reattach the lid and let a blanket of CO2 keep the beer safe as the yeast fall out of suspension. (I may even give it a blast of CO2 from my kegging system). Then transfer by gravity with a hose into my keg, disturbing as little as possible to keep any oxygen damage at bay.

I chose to test my coolship on my cheap extract saison to work out the kinks before I use it with a long 7 hour brew day Hefe. Bonus is that it will be served at a festival in 5 weeks to 4000 people, so if it's not 100% awesome, they will be too drunk to know.
My intention is to keep this tread updated with results, tasting notes and to be a place for others doing something similar to comment on their experiences as well.




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[mcbethenstein]

A few more of the hop drive and skimming. The krausen wasn't as high tonight, so I sealed the fermenter. The aroma was brilliant. Phenolic, spicy, fruity, cherries, citrusy perhaps from hops, very high on esters. Hopefully it will finish dry like the last time with a hint of tartness, like a good saison should be. This is looking to be very Belgian in profile. So far seems a success. Hopefully the rest of the process goes smoothly. If I recall correctly the last time I used this yeast (Wyeast 3726 farmhouse) it was done in about 4 days. And finished at 1.004. Perfect for a saison.




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[Bamsdealer]

Hope its exactly what you were aiming for. Cool thread

 

[sandyeggoxj]

Open fermentation is a great art form. Looking forward to see how this turns out!

 

[beersk]

Awesome! Can't wait for the results... But do you think decoction is REALLY adding to your beer? I'm skeptical of that part. Many German breweries don't even decoct anymore.

 

[g-star]

Great work! Looking forward to your results.

 

[Mer-man]

Really cool!

 

[chewse]

Really like the concept! Open fermentation seems to align with old world brewing techniques. Very interest in hearing about your analysis.

 

[Xpertskir]

A coolship that is not. Good luck with your hefe though.

 

[DSorenson]

I don't really think that constitutes "open fermentation" as demonstrated by Samuel Smith's fermenters.

That said, I do see some evidence from your reading material (source?) that the shape of the fermenter plays a roll in flavor. That is interesting to me and quite honestly I would believe it. It would make the pressure in the wort a the bottom of the fementer less, for instance. It would also change how the yeast stay in contact with the beer.

Very cool thread. I work with a rather small fermentation chamber that can only comfortably fit one carboy. I will consider playing around with vessels like this for the conservation of space... maybe allowing me to ferment out more beer at a time.

 

[mcbethenstein]

I know it's NOT really a coolship, but what else do you call a shallow flat open fermenter?


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[mcbethenstein]

For this saison, I wasn't ready to leave it fully open. It was cracked, but my basement is a typical basement and the wort needed a little protection from the elements, while still allowing for oxygen & CO2 exchange. When I do my Hefe it is truly open. And will be in a darker and cooler part of my basement.


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[mcbethenstein]

Awesome! Can't wait for the results... But do you think decoction is REALLY adding to your beer? I'm skeptical of that part. Many German breweries don't even decoct anymore.

I question that as well, since a few times "brewing with wheat" referenced franzisksner doing taste trials with their Hefe and the average consumer not being able to tell the difference as well as Sierra Nevada doing a single infusion for kellerweis... But I am a super taster, and I am fairly certain I can tell side by side.... Perhaps another experiment will be needed to verify.


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[mcbethenstein]

My update on the saison. This morning the fermenter is sitting happily at 74° F, a nice temperature for a saison. The aroma is extremely estery, but in the best way. Krausen has started to fall, and checking the airlock, the headspace in my closed up fermenter is definitely filled with CO2. I know that this fermenter isn't truly an open fermenter, but it is a way to combine the best attributes of all the different techniques. Shallow and flat to reduce osmotic pressure on the yeast allowing them to create more esters and phenols, removable lid to allow for oxygen and CO2 exchange (again allowing the yeast to happily create more esters, since ester production goes down as dissolved CO2 goes up), and sealable after the point of hop drive & high krausen to eliminate the risk for infection and oxidation after fermentation. It may not be 100% traditional, but short of building a dedicated clean room for a real open fermenter and transferring to a secondary immediately after fermentation is 90% complete, I think it's working out nicely so far.

 

[progmac]

I know it's NOT really a coolship, but what else do you call a shallow flat open fermenter?


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i'm fine with the term. i think it accomplishes the same thing. cool post, keep us updated!!

 

[DSorenson]

For this saison, I wasn't ready to leave it fully open. It was cracked, but my basement is a typical basement and the wort needed a little protection from the elements, while still allowing for oxygen & CO2 exchange. When I do my Hefe it is truly open. And will be in a darker and cooler part of my basement.


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Honestly, does anyone know why truly open fermentation does to improve beer?

I think your current setup is great. Covered will ultimately make you less nervous.

 

[botigol]

my basement is a typical basement and the wort needed a little protection from the elements, while still allowing for oxygen & CO2 exchange. When I do my Hefe it is truly open. And will be in a darker and cooler part of my basement.


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Maybe a compromise between truly open and having a good measure of protection would be a polyester sheer window curtain. It is thin and light, so you should be able to secure it well enough not to sag into the wort/beer and it has sufficient breathability to allow the exchange of gases, but it has a tight enough weave to prevent a lot, maybe most, dirt and dust from penetrating.

 

[beersk]

Honestly, does anyone know why truly open fermentation does to improve beer?

I think your current setup is great. Covered will ultimately make you less nervous.

I don't know if it's the fact that it's truly open so much as the geometry of the fermenter.

 

[mcbethenstein]

I don't know if it's the fact that it's truly open so much as the geometry of the fermenter.

At this point I'd put money on the geometry over open factor. I've done a number of open fermentations, all in a 7 gallon bucket with lid offset by an inch, lid completely off with my filter bag covering it, and even just completely off. All the results have been similar, and just not as pungently ester-y as this one has been so far.


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[Twinkeelfool]

I recently tried a porter in this. Like you I've read a few places about fermentor geometry having an effect on flavour profiles. I think it worked well enough I'm going to do it again. For me, the ester profile was very nice, subtle but more pronounced. Purely anecdotal at the moment, but like I said, it was very nice and my next batch will be an english IPA.

I think the shallow, wide fermentor gives the yeast more surface area exposed to oxygen, which is apparently much less stressful for the yeast, not so much that it's an open ferment. No expert though.

I do mine in my ferm fridge, and only leave it for the first few days. I top crop, then siphon into a standard fermentor to finish off.

I've been thinking of doing a saison in mine, dupont apparently uses short,wide fermentors, though they are closed. Someone here posted a link the other day to a 10 page article about dupont, which had a pic.

 

[tagz]

Enjoyed you're other jefe thread. Looking forward to the results.

 

[mcbethenstein]

If my new Refractometer is calibrated correctly and I can trust the online calculators for SG conversion from brix, I'm at final gravity. 1.003 or 1.004. I'll transfer to keg and take a hydrometer reading tonight to verify. The saison is hugely estery. About 2-3 times more estery than at this point last time. I'll taste a bigger sample later and figure out if it has the tartness the strain is know for. If not it might need a few drops of Lactic Acid to balance out all those esters. Results are very promising.


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[mcbethenstein]

Here are some photos from the transfer. Seriously easiest transfer I've had in a long time. I put the fermenter up on my freezer yesterday to let it settle before moving to keg. Yeast cake was well set.

Saison has cleared nicely, and the transfer did not pick up much, if any sediment.

I did need to tip the fermenter to get the rest if the beer out, but done carefully, it did not disturb the yeast cake/ sediment.

Here you can see the PVC elbow. It really helps pick up beer without pulling in extra oxygen.


Finishing gravity was 1.004. The samples are very estery, and there is the tartness/ dry finish that makes it refreshing. It will carb in the keg for a few days then I'll check how it tastes officially.


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[DSorenson]

Very excellent work.

I appreciate the amount of research you did to make this happen.

 

[henchman24]

I'm going to try this with a future batch. I don't have a clean enough area to actually open ferment (damn spiders), but this might bring some of the esters that I want.

Can't wait to hear about it when it is carbed up. :rockin:

 

[Paps]

Sorry if you allready posted it and i missed it but could you throw up a link to that info regarding fermentor shape and ester production please.

 

[Twinkeelfool]

There are passages in some brewing books. The "yeast" book has a passage mentioning that different fermentor geometry will definately throw different flavours.

There are snippets in some others also, I believe dupont use them as well.

I've done it once, but am keen to do it again, it produced a great porter.

Macbeth, I found that it seems to take away, or smooth out some of the bitterness in the porter I did. Could just be a placebo though. Have you noticed any changes ?

 

[mcbethenstein]

Sorry if you allready posted it and i missed it but could you throw up a link to that info regarding fermentor shape and ester production please.

Not a link, but the 2nd photo in the first post is the chart. It's from "brewing with wheat" mid chapter in the German Hefeweizen section.


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[mcbethenstein]

Here's my final update on the Saison. I have not yet had time to brew my Hefe... But my basement is pretty close to optimal temp for a well controlled Hefe at 63-66°F. I served the saison keg at Great Lakes brew fest this Saturday. The beer was well received. No indication of oxidation, and the ester character was phenomenal. Definitely my fruitiest saison yet. The slight sour/tart dryness from the yeast was still there, but fairly subdued... Or should I say overpowered by the esters. Profile of esters: Slight cloviness, medium banana, slight bubblegum, huge stone fruit (cherries, plum and apricot). I walked away with a good 1/2 keg left so I may pump up the CO2 a bit more and see how it ages. Could benefit from a little dose of Lactic Acid (maybe 1mL) to balance it out a little more, but definitely is not necessary.


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[Xpertskir]

i'm fine with the term. i think it accomplishes the same thing. cool post, keep us updated!!

It is not a coolship, not even a little, and it accomplishes nothing that a coolship accomplishes.

It is a rectangular fermenter that the OP is pseudo open fermenting(which may or may not do anything to produce a different beer).

I would be interested to use differently shapes of fermenters, but it would be difficult to ascertain any difference without a side by side batch in a cylindrical fermenter.

 

[DSorenson]

It is not a coolship, not even a little, and it accomplishes nothing that a coolship accomplishes.

It is a rectangular fermenter that the OP is pseudo open fermenting(which may or may not do anything to produce a different beer).

I would be interested to use differently shapes of fermenters, but it would be difficult to ascertain any difference without a side by side batch in a cylindrical fermenter.

I believe the OP's source did more than enough to show evidence that fermenter geometry has an effect on the finished product.

I commend OP on a job well done and on the brave choice to risk beer in the pursuit of perfection.

 

[orangehero]

I believe the OP's source did more than enough to show evidence that fermenter geometry has an effect on the finished product.

I commend OP on a job well done and on the brave choice to risk beer in the pursuit of perfection.

I would guess when dealing with homebrew size fermentors the geometry is completely irrelevant. Anything you can ferment a 5 (or even 10) gallon batch in is probably more shallow than a "shallow" commercial fermentor.

 

[DSorenson]

I would guess when dealing with homebrew size fermentors the geometry is completely irrelevant. Anything you can ferment a 5 (or even 10) gallon batch in is probably more shallow than a "shallow" commercial fermentor.

We don't really know what is causing this effect, but allow me to make a case:

- What if it is pressure dependent?
If the cause of greater ester production is inversely proportional to pressure in a hydrostatic fermenter, we would very likely notice a difference between commercial and homebrew scale conical fermenters. I say this because the pressure is completely height dependent. The deeper the fermenter, the greater the pressure at the bottom. Since pressure increases linearly (rho*g*h) we know that more beer is exposed to greater pressure in taller tanks. The inverse would be true for homebrew carboys. I hope this has made my case against this idea.

Disclaimer: I am not knowledgeable on large scale brewing concerns, and I welcome anyone with experience to chime in. I have not heard of this being an issue for big brewers, and I am aware that some people ferment under pressure.

-What if the cause is purely in the geometry?
Well we still don't know what's causing the effect; surface area to air, beer contact with flocculated yeast... etc. This asside, we can say is that geometry between commercial and homebrew levels can be proportional. We can compare a commercial shallow fermenting rectangular prism or cube and compare it (using ratios) to one of homebrewing volume.

That is to say that the effects of geometry would be proportional, and therefore similar. We already have an idea about this, since the same beer can be brewed in an 80 hectoliter cylinder as in a 20 liter cylinder.

I think in the end, the OP can speak for it's effectiveness. You might argue placebo, but all anecdotal information is subject to this type of scrutiny.

 

[orangehero]

What effects are you specifically talking about and why are you assuming the effects of geometry are proportional (aside from pressure)?

The depth of liquid (and static pressure) in homebrew sized vessels is less than the shallowest of commercial tanks. On the commercial scale the difference in pressure between a cylindroconical vessel and a shallow fermentor are significant. Not so when you're talking about 8" difference in liquid level between a carboy and a plastic tub.

 

[DSorenson]

What effects are you specifically talking about and why are you assuming the effects of geometry are proportional (aside from pressure)?

The depth of liquid (and static pressure) in homebrew sized vessels is less than the shallowest of commercial tanks. On the commercial scale the difference in pressure between a cylindroconical vessel and a shallow fermentor are significant. Not so when you're talking about 8" difference in liquid level between a carboy and a plastic tub.

Stick with me, here.

In response to the pressure part:

If we assume that a characteristic of fluid mechanics is responsible for ester increase, then that characteristic would be pressure. Since the pressure goes down in a rectangular prism fermenter, then the ester production goes up when the pressure is less, via our first assumption.

If that was true, then the difference in pressures between commercial brewing and home brewing would be immense and homebrewers would notice increased ester production (relative to style) in every beer we made as opposed to commercial.

This is why I do not believe that increased ester production is a function of pressure.

In response to the geometry part:

We can look at proportionality between any characteristic of a 3D shape and it's volume. It will be a constant value.

Say you have a cubic fermenter that holds some volume "V" of wort and has a base area "A" at the bottom. You can compare, for instance, the area of the base of the fermenter with the volume it caries:

A/V=C

Where "C" is your base area to volume ratio. If you wanted to make a fermenter that holds more volume "V" and maintains the same base area per volume ratio, then you can construct a fermenter with an equal base area per volume:

C*V=A,

Where "A" is the product of the lengths of two adjacent sides of your rectangular base.

The point of this is, in short, that we keep the attributes of what the beer is contacting the same. Two fermenters constructed proportionally in this manor will sit on the same area of flocculated yeast per unit volume of beer. Or it will be in touch with the same area of surface area to air per unit volume.

We must be able to surmise that ester production is proportional to some characteristic of the shape of the fermenter, and not the pressure of the fluid within.

In other words, pressure is the only property at work here for which scale could account for differences. Since pressure is not a likely suspect, then it only leaves the actual shape of the fermenter. Since the shape of a fermenter can be proportional for any unit volume, scale does not matter.

 

[orangehero]

If we assume that a characteristic of fluid mechanics is responsible for ester increase, then that characteristic would be pressure. Since the pressure goes down in a rectangular prism fermenter, then the ester production goes up when the pressure is less, via our first assumption.

It is known that increased pressure suppreses ester production. Because of this reason, commercial brewers are able to ferment at higher temeratures in cylindroconical vessels compared to shallow fermentors and still get the same ester profile.

If that was true, then the difference in pressures between commercial brewing and home brewing would be immense and homebrewers would notice increased ester production (relative to style) in every beer we made as opposed to commercial.

This is exactly what happens. What we do as homebrewers to make a particular beer is not necessarily what is done on the commercial scale. You're assuming that all of these parameters scale linearly in their effects based on batch size, but it's not that simple.

I'm skeptical that differences in surface area at this scale (e.g. between a carboy and a plastic tub) really makes any difference, whether due to contact with flocced yeast or exposure to air (which shouldn't really be happening after CO2 production begins) or whatever else.

 

[DSorenson]

I'm skeptical that differences in surface area at this scale really makes any difference, whether contact with flocced yeast or exposure to air (which shouldn't really be happening after CO2 production begins)

If you can make it out, OP's first post has a picture of the book he got it from. Read the paragraph or two just above the chart, if you can make it out.

edit: for the record, I can understand your skepticism. Also, very cool- didn't know that pressure actually had an effect. Would you happen to have any sources on that?

Also, it looks like the open fermentation is truly the only way to substantially increase esters, from what that chart says.

 

[orangehero]

I have that book, and like I said I'm skeptical that it translates to homebrew scale. I haven't done the calculations, but I doubt that the height of 5 gallons in a slim cornelius keg (that's not pressurized) really creates enough of an increase in pressure than the height of 5 gallons in, let's say presumably a carboy, to result in a noticable difference in ester production as Stan Hieronymus proposes. The paragraph also explains why pressure is the factor at work (by increasing CO2 concentration).

If you get any books on lager brewing they are all about decreasing ester production.

 

[Twinkeelfool]

Ever tried it ?. I have and I'm planning on doing it again, because I liked the results a lot. It's about keeping the ratio of height to width at 1:1 or less. Why does it work? Don't know.

 

[DSorenson]

I have that book, and like I said I'm skeptical that it translates to homebrew scale. I haven't done the calculations, but I doubt that the height of 5 gallons in a slim cornelius keg (that's not pressurized) really creates enough of an increase in pressure than the height of 5 gallons in, let's say presumably a carboy, to result in a noticable difference in ester production as Stan Hieronymus proposes. The paragraph also explains why pressure is the factor at work (by increasing CO2 concentration).

So I did a little math:
The x axis is the radius of the fermenter (cylindrical) in meters and the y axis is the pressure at the bottom of the fermentor in Pascals. (metric was just easier). Here, I am using 5 gallons of water just for reference (18.9 L).

It does seem to me that these pressures are not that significant when compared to pro brewing setups. A 6 gallon better bottle filled with 5 gallons of water has a radius of about .145 meters and has an ultimate pressure of 2824 Pascals. (about 3% of the atmospheric pressure at sea level)

This is nothing compared to a 1:1 height:diameter (cylindrical) ratio for an 8000 liter setup (80 hectolitres), which is 212439 Pa. That is roughly two times the atmospheric pressure at sea level.

Okay, so now we know what we are dealing with here.

I will say this: If it's true that larger breweries adjust for pressure differences when brewing in a "standard" vessel, then the results of homebrew ideally mimic those of a larger scale. With this in mind, perhaps scaling down the pressure for either results in increased ester production.

In other words, perhaps the effect is the same even if the pressure differences are huge?

This would be easier to figure out is someone would just give me some formulas relating pressure and brewing...