Spunding for Dummies

[Vale71]

If you were to spund the beer to 15 PSI you'd have to leave exactly half of the fermenter volume empty to have enough pressure to transfer the whole volume of beer without supplemental CO2. If you did you would then run into the issue of transferring somewhat carbed beer at an ever dwindling pressure which might cause serious foaming issues. I'm afraid you'll have to either try your hand at gravity transfer or accept the need for bottled CO2 as propellant.

 

[Vale71]

I know fermenting under pressure can suppress esters, but I have never found any data to indicate it suppresses phenols. Do you (or anyone) know of any?

Pressure fermentation also suppresses higher alcohols of which phenols are a subgroup so I'd expect pressure to suppress their expression as well. Anyway I'm not sure how much of an effect it will have compared to the usual parameters such as yeast strain and level of precursor in wort.

 

[VikeMan]

Pressure fermentation also suppresses higher alcohols of which phenols are a subgroup so I'd expect pressure to suppress their expression as well.

I know that some higher alcohols are phenol derived, but since when are phenols a subgroup of alcohols? i.e. AFAIK chemist define alcohols and phenols separately.

 

[Vale71]

You're right, my bad.

 

[ChiknNutz]

Pretty happy with how this is going so far.

 

[Bassman2003]

Cool. Glad to hear of your progress. The procedure is pretty easy, just finding the right time is what takes some effort.

 

[Yesfan]

Subscribed.


I have a 10G batch of pale ale I'm kegging later tonight. I'm new to spunding too, but this batch I attached the valve to my conical after fermentation started to slow down. Has been holding at 10psi the past couple of days.

 

[RePete]

Following. I was going to buy a Kegmenter and haven’t yet. Interested in you results.

 

[Steven Barrett]

Seems like a lot of you are using your spindijg valve to carbonate in the fermenter and then transfer the carbonated beer to the keg. Can anyone explain why? I thought the typical process was to ferment under atmospheric pressure, then transfer the beer with a few gravity points to go into the keg then close the keg and the spunding valve is there to bleed off any excess pressure in case you transferred it with too many gravity points remaining.

 

[bmullins393]

Round 2. Made my first BIAB batch last Sunday, an Orange SMaSH Ale. My plan was to transfer from fermenter to keg after 3 days this time so I would have a better chance of active fermentation. Went ahead and did that last night. Also took a hydrometer reading, came in at 1.025 and my planned FG is 1.018 so I think I am in good shape for spunding.

Relocated spunding valve from fermenter to keg and increased the pressure to around 25-30 psi (it's not exact until it reaches pressure, though it is fairly accurate in psi per revolution). After a few hours, noticed it had already increased to about 5 psi. This morning it was about 28 psi, which is actually just about right for 2.4 volumes at 72 degrees. I bled some off as I thought my target was 25 psi, but went into the calc again afterwards and think I want to shoot for 2.4 volumes, so cranked up again, shooting for around 28 psi.

Overall I do like this process. One issue I've discovered is though I intentionally allow a low psi during initial fermentation (around 5 psi max) so that I can use that pressure for the transfer, I am finding that is inadequate and still need to supplement with bottled CO2. I was not so impatient this time and let the transfer go for a few hours using the original pressure, but it seemed to stall. I then hooked up the CO2 and let it go for another hour or so. That completed the transfer but I thought part of the goal was to use the CO2 for the transfer. I could of course increase the pressure during fermentation, but it seems the jury is out on whether or not it's a good idea to ferment under pressure.

Thanks for sharing your experience! Truly helpful!

 

[VikeMan]

Seems like a lot of you are using your spindijg valve to carbonate in the fermenter and then transfer the carbonated beer to the keg. Can anyone explain why? I thought the typical process was to ferment under atmospheric pressure, then transfer the beer with a few gravity points to go into the keg then close the keg and the spunding valve is there to bleed off any excess pressure in case you transferred it with too many gravity points remaining.

Personally, I don't spund to full carbonation levels in the fermenter. Think about autolysis, which "never" happens in homebrew. (Not really never, but people like to say it.) I think the reason it is so rarely happens to a noticeable level in homebrew is because yeast in homebrew fermenters doesn't normally see the kind of hydrostatic pressures that big (tall) commercial fermenters see. But when you increase pressure to the levels you need for carbonation, you're now exceeding what the tall (unpressurized) conicals see.

 

[bmullins393]

Personally, I don't spund to full carbonation levels in the fermenter. Think about autolysis, which "never" happens in homebrew. (Not really never, but people like to say it.) I think the reason it is so rarely happens to a noticeable level in homebrew is because yeast in homebrew fermenters doesn't normally see the kind of hydrostatic pressures that big (tall) commercial fermenters see. But when you increase pressure to the levels you need for carbonation, you're now exceeding what the tall (unpressurized) conicals see.

Curious.... what vessel do you use for pressure fermenting/spunding? Is it tall and thin like a corny keg? Or more squat like a flex or fermentasaurus? Does shape make the difference?

 

[VikeMan]

Curious.... what vessel do you use for pressure fermenting/spunding? Is it tall and thin like a corny keg? Or more squat like a flex or fermentasaurus? Does shape make the difference?

I ferment most batches in a MoreBeer 7.5 gallon conical, under low (~ 2 PSI) pressure, controlled by a spunding valve. The profile is more like a flex than a corny, but height doesn't really doesn't matter at that scale... the differences in hydrostatic pressure would be miniscule.

When I spund for carbonation, I do that in a corny keg.

 

[Vale71]

Personally, I don't spund to full carbonation levels in the fermenter. Think about autolysis, which "never" happens in homebrew. (Not really never, but people like to say it.) I think the reason it is so rarely happens to a noticeable level in homebrew is because yeast in homebrew fermenters doesn't normally see the kind of hydrostatic pressures that big (tall) commercial fermenters see. But when you increase pressure to the levels you need for carbonation, you're now exceeding what the tall (unpressurized) conicals see.

The tall conicals are pressurized up to 3 bar if doing warm lager fermentations. The reason they don't see autolysis is because they regularly dump yeast. The beer also gets packaged as soon as two weeks after pitching, which is the whole point of accelerated lager fermentation, so the yeast still in suspension has no time to start autolysing.
Autolysis happens simply because without nourishment yeast cells eventually die and decompose. This happens regardless of hydrostatic or headspace pressure. To actually start mechanically damaging yeast you'd need unbelievably high pressures or ultra-centrifugation. The reason most homebrewers don't detect autolysis is probably because they either can't or it's overshadowed by other, more promiment defects, first and foresmost cold-side oxidation.

 

[ChiknNutz]

Seems like a lot of you are using your spindijg valve to carbonate in the fermenter and then transfer the carbonated beer to the keg. Can anyone explain why? I thought the typical process was to ferment under atmospheric pressure, then transfer the beer with a few gravity points to go into the keg then close the keg and the spunding valve is there to bleed off any excess pressure in case you transferred it with too many gravity points remaining.

To clarify...I started in the fermenter with the spunding valve under low pressure (<5 psi), could have been 0 psi really. I was hoping that this low pressure would be enough to allow for a pressurized transfer but it is not. As @Vale71 noted, I would need more pressure and head volume to fully accomplish this. One reason I started with some pressure is based on the info I rec'd from the maker of this particular spunding valve, which I was not aware of until our exchange. In his listing he says to not started at 0 psi since the initial fermentation can actually create a vacuum, which I first questioned...below is his reply.

Yeast is one of a few microorganisms that can live:
1. Aerobically (in presence of oxygen) known as facultative phase when it consumes oxygen to reproduce - making more yeast.
2. Anaerobically (without oxygen) known as fermentative phase to make alcohol.
So right after adding the yeast, it will eat the oxygen in the headspace of the fermenter or about 20% of the air to make more yeast. That s how a vacuum will develop if everything is closed tight. Brewers need to have enough yeast for their fermentation, so they add oxygen to their wort by either inject pure oxygen or stirring/rocking vigorously to oxygenate it before pitching the yeast.
As soon as the oxygen is consumed, the yeast will switch to fermentative phase to make alcohol.
To avoid sucking in water from airlock or our FERMonitor, we recommend setting the pressure relief valve to about 2 psi (or 3 turns cw).

I then transferred to the keg at day 3 and cranked up the spunding valve to what you see in my latest post. At this point fermentation is slowing but the residual fermentation is what is creating the pressure so it can naturally carbonate. The keg is at ambient temp which is why you see it near 30 psi. Now at day 4-1/2 I just visually checked it before this writing and do have some airlock activity, as expected. I will leave this for probably another week so it can finish fermentation and fully carbonate. After this it can go in the fridge/kegerator.

 

[Vale71]

To put it somewhat bluntly: the manufacturer of this particular piece of equipment is full of it.
Yeast cannot consume the O2 that is in the headspace, the very idea is beyond ludicrous. Yeast don't have tiny lungs with which to inhale atmospheric oxygen, they'd have to wait for diffusion to transfer it to the liquid and that would take weeks if not months. That's why we aerate wort before pitching, because the O2 we dissolve in the wort is the only O2 the yeast will be able to absorb before switching to anaerobic fermentation, which wil produce copious amounts of CO2 that will gradually purge the headspace of any other gas.

 

[Yesfan]

So is it better to spund as fermentation starts to decline? I like the idea some of you are doing to use the fermenter's co2 pressure to purge your kegs but do you worry about any blow-off material getting through and possibly clogging the disconnect on your keg?

 

[ChiknNutz]

Well there you go. Not knowing all the particulars, I had no reason to question it at the time. Regardless, it is a quality product.

 

[Vale71]

So is it better to spund as fermentation starts to decline?

Definitely, unless your purpose is to do pressure fermentation and you know what you are doing and why.

 

[ChiknNutz]

...but do you worry about any blow-off material getting through and possibly clogging the disconnect on your keg?

Not if there is adequate head space. For me, I do ~5G batches (last one was likely 5.25G into the fermenter) and the fermenter is 7.6G capacity.

 

[VikeMan]

This happens regardless of hydrostatic or headspace pressure. To actually start mechanically damaging yeast you'd need unbelievably high pressures or ultra-centrifugation.

So you are saying that pressure doesn't matter at all vis a vis autolysis? Opinion or data?

 

[Yesfan]

Not if there is adequate head space. For me, I do ~5G batches (last one was likely 5.25G into the fermenter) and the fermenter is 7.6G capacity.

I've noticed bits of krausen in my blow off jar and that was with about 2-3 gallons of head space in my conical if you count the dome portion of the lid. I'm not so worried when most of the active part of fermentation has passed, but wonder with a pressurized fermentation from the start.

 

[VikeMan]

So is it better to spund as fermentation starts to decline? I like the idea some of you are doing to use the fermenter's co2 pressure to purge your kegs but do you worry about any blow-off material getting through and possibly clogging the disconnect on your keg?

There's nothing wrong with spunding (at low pressure) from the get go. But you do have to know your equipment, batch size, gravity, yeast strain behavior, etc. i.e. you need to be sure that there will be no blow-off, unless you want to ruin a spunding valve.

 

[Vale71]

So you are saying that pressure doesn't matter at all vis a vis autolysis? Opinion or data?

Not at the pressures that can be reached in beer fermenters. It's what's taught in all brewing schools so I'm pretty sure it's not uninformed opinion.
Mind you, excessive hydrostatic pressure will affect fermentation profile and performance, which is why even the largest industrial fermenters are limited to about 8 meters height. That and structural considerations, but not becuase of concerns with autolysis.

EDIT: Here is a research paper (only the abstract is free) on the subject of inducing autolysis in yeast to produce natural flavor enhancers for winemaking (autolysys is desirable and sought after in certain types of wine). The best results were obtained with a pressure of 150mPa or 21,755 PSI (that is not a typo!). This gives you an idea of how hardy the beasties are.

 

[bmullins393]

The tall conicals are pressurized up to 3 bar if doing warm lager fermentations. The reason they don't see autolysis is because they regularly dump yeast. The beer also gets packaged as soon as two weeks after pitching, which is the whole point of accelerated lager fermentation, so the yeast still in suspension has no time to start autolysing.
Autolysis happens simply because without nourishment yeast cells eventually die and decompose. This happens regardless of hydrostatic or headspace pressure. To actually start mechanically damaging yeast you'd need unbelievably high pressures or ultra-centrifugation. The reason most homebrewers don't detect autolysis is probably because they either can't or it's overshadowed by other, more promiment defects, first and foresmost cold-side oxidation.

Thanks for this info... I am learning...

What is Hydrostatic pressure? What effect does it have on fermentation under pressure?

Thanks!

 

[Vale71]

In any case, even though pressure is definitely a stress factor for yeast, it is by no means the only one.

Setting aside any quantitative considerations, saying "Pressure increases yeast autolysis. Pressure in our small unpressurized fermenters is negligible therefore we never experience autolysis in our home brews" makes as much sense as saying "Jumping off of a tall building means certain death. It follows that if you never jump out of tall buildings you'll live forever."

That is just wishful thinking on the part of the homebrewers. Autolysis is a part of the lifecycle of yeast (the terminal one, actually) and will happen in any case. There are many factors influencing the speed and the extent of it, such as yeast vitality, pitch rate, oxigenation rate and last but not least time and temperature. Anybody who thinks that it's safe to leave beer on a yeast cake for 6 months is just fooling themselves. On the other hand unpackaged beer will be so severely affected by oxidation after 6 months that autolysis probably won't matter anyway.

 

[Vale71]

Thanks for this info... I am learning...

What is Hydrostatic pressure? What effect does it have on fermentation under pressure?

Thanks!

It's the pressure you experience when immersed in a liquid that is proportional to the depth of immersion. To give a practical example, it's the pressure a deep see diver experiences during a dive.
Its effects on yeast are identical to the effects of headspace pressure since yeast cannot distinguish between the two types of pressure. In practice yeast will experience a total pressure that is equal to hydrostatic plus headspace pressure.
It affects yeast metabolism in several ways, first of all making it slower and then suppressing the production of aroma active substances like esters and fusel alcohols. Taken to extremes it can slow down yeast's performance to the point that you can get a stuck fermentation with possible stratification in very large fermenters, so that you could have fully fermented beer on top and only partially fermented beer in the bottom.

 

[Steven Barrett]

Assuming a 30 ft tall fermenter full of wort, the pressure at the bottom will be about 13 psi higher than the pressure at the top. Whereas if your fermenter is 3 ft tall, the pressure at the bottom is only 1.3 psi higher.

 

[bmullins393]

It's the pressure you experience when immersed in a liquid that is proportional to the depth of immersion. To give a practical example, it's the pressure a deep see diver experiences during a dive.
Its effects on yeast are identical to the effects of headspace pressure since yeast cannot distinguish between the two types of pressure. In practice yeast will experience a total pressure that is equal to hydrostatic plus headspace pressure.
It affects yeast metabolism in several ways, first of all making it slower and then suppressing the production of aroma active substances like esters and fusel alcohols. Taken to extremes it can slow down yeast's performance to the point that you can get a stuck fermentation with possible stratification in very large fermenters, so that you could have fully fermented beer on top and only partially fermented beer in the bottom.

Thanks so much for the great explanation. I had to read it twice but I got it now. I really enjoy the science of all this...

 

[bmullins393]

Assuming a 30 ft tall fermenter full of wort, the pressure at the bottom will be about 13 psi higher than the pressure at the top. Whereas if your fermenter is 3 ft tall, the pressure at the bottom is only 1.3 psi higher.

That makes sense... thanks!