Fermentation stuck at 1020

[krz]

Hi,

I have made 45 litres of IPA wort (with the Guten) at 1048 and into the Conical fermenter it went.
I have an oxygen wand, and I added about 3 minutes of oxygen prior to adding yeast.
I added enough US05 yeast and sealed the conical to ferment under presssure.
I have been doing pressurised fermentation for some time now, and only one issue (now two) The last ferment I did, I also had a stuck fermentation, so I added some more yeast and it completed to 1010.
Now this time, once again it got stuck and I added more yeast 4 days ago, but still sits at 1020.

I extracted a glass of beer today and added some fresh bakers yeast, I'll leave ifor 2 days to see if the gravity changes.
Not sure what to do now. Any suggestions?

 

[Lionman]

What pressure/temp are you fermenting at?

What grist did you use?

What mash schedule?

 

[Schikitar]

Most importantly, how does it taste? My XPA was supposed to get to 1.012 but only made it to 1.016 - tastes great though so into the serving keg it goes!

 

[krz]

What pressure/temp are you fermenting at?

What grist did you use?

What mash schedule?

I roughly followed Walt's India Pale Ale recipe from Beersmith, which is mostly Pale Ale malt with some crystal, Wheat and I used double Caraaroma instead of Victory malt.
I also used US05 instead of Wyeast #1968.

Mash was 90 minutes at 62C

Funny enough, you made me look at the recipe just now and I notice that FG should be 1018 not 1010. So I guess my beer is ready

The yeast I put in the glass of wort yesterday hasnt reacted, so I guess its fully fermented.

Ive just cranked up the temp to 23.5C, I'll leave if for 2 days then start the crash cool and keg!!!


Note: Pressure fermented at 20 PSI, 22C but after I added the extra yeast it hasnt exceed 10psi.
I guess that was just the absorbed CO2 escaping pressuring the vessel.

 

[laxation]

I had the same issue a few weeks ago - have a read here for some tips. I think if I left mine longer the cbc would have worked.

 

[Dan Pratt]

If you mashed the beer at 62c the software will not calculate the FG correctly, so a 1018 on the software is incorrect.

You should achieve a 1008 - 1010 from that temperature of the mash so if you havent got that yet you need to re-check, like mentioned taste it to see, a 1020 will be quite sweet.

 

[Lionman]

What are you brewing in? Are you measuring the mash temp accurately?

How are you measuring the SG?

I'd suggest backing off the pressure to about 1 bar (15psi). Not all yeast respond favourably to pressure either. Give Nottingham a go.

 

[keine_ahnung]

Hey krz,

I'd be interested to hear your logic on fermenting under pressure...

With an FG of 1020, your attentuation would only be at around 58%. That's pretty damn low/sweet...

There are quite a few gaps in the info above, but ASSUMING you've reached iodine-normality, with a single mash rest at 62deg, I'd expect a FG 1048 beer to come down considerably lower than 1020. However, this is of course affected by your maltbill. What exactly does "mostly Pale Ale malt, with some crystal......" mean? 75% Pale Ale, or 85% or 95%?

With just this rest, you're completely relying on the ß-Amylase to break down the starch (well...and little bit of help from Saccharase and End-Dextrinase, but that's probaby negligible).
Two critical factors spring to mind here:
- pH... ß-Amylase likes it between 5,4-5,6. If you happen to have a mash at 5,8....this could be a bit problematic without an alpha-amylase rest.
-Gelatinisation!!! Even more critically, if the gelatinisation-temperature of your malt happens be above 62deg (typically 60-67deg for barley, depending on season), then the ß-Amylase can barely work away at the starch.

IF this were the case, it is possible that the 62deg rest pretty much does/did nothing, then as you heat up to mash out at 78 degrees, the malt gelatinised, then still had 10-15 mins where the ß- and Alpha-amylase were active. This would potentially be enough time to account for the 58% conversion of starch to fermentables.

^ a possible theory. Not saying this is necessarily what's happened. But it's good to consider what actually happens during the mash and how that affects the fermentation.

Do you know what the gelatinisation-temp of your malt is?
Did you do an Iodine-test?

As lionman has said, it is possible that the yeast isn't coping with the preasure so well...
This is definitely possible, however seems a bid odd for a few reasons.
1. you seem to have had good results with your fermentation process so far.
2. In the brewery where I previously was, we brewed regularly with US05, and never had a problem with it "stopping" due to pressure. We never "fermented" under pressure (not sure why one would for an ale to be honest...never heard if it until now), just closed the fermenting tank at around 80% of the way throught the fermentation to ensure carbonation...as per usual, and then let it finish fermenting, then condition, etc.
But as said, never once had a problem with the yeast here. Even up to 1.8bar...

 

[///]

Check your thermometer is reading the correct temp, the pH and yeast health. Main 3 issues why yeast poops out.

Even though you pumped oxygen in it does not mean it dissolved. When I used to run Ringwood ale I would pump on fot the first 24 hours

 

[krz]

H..........
This is definitely possible, however seems a bid odd for a few reasons.
1. you seem to have had good results with your fermentation process so far.
2. In the brewery where I previously was, we brewed regularly with US05, and never had a problem with it "stopping" due to pressure. We never "fermented" under pressure (not sure why one would for an ale to be honest...never heard if it until now), just closed the fermenting tank at around 80% of the way throught the fermentation to ensure carbonation...as per usual, and then let it finish fermenting, then condition, etc.
But as said, never once had a problem with the yeast here. Even up to 1.8bar...

Thanks for your informative reply (No Idea). A lot of it I was beyond my knowledge.
I use pressure for following reasons:-

1. Reduce time of fermentation
2. Limit effect of a diaacetyl (theory)
3. Reduce noise of fermenter (close living space)
4. Naturally carbonate beer

Anyway, as /// says, maybe the thermometer is a problem.

Thanks all for response

 

[wide eyed and legless]

Fermenting under pressure doesn't reduce time of fermentation, also, even at low pressures can cause the fermentation to stall and it also increases the chance of acetaldehyde, even at low pressure (7psi)

Knatchbull and Slaughter14 outlined the effects of low CO2 pressures on the production of flavour-active volatiles by yeast. They showed that CO2 pressures of 0.5 and 1.0 aim (100 kPa) lead to reduced fusel oil and ester concentrations whereas acetaldehydc levels were increased. Kruger et «/.15, using protein-based "yeast foods" to lower dissolved CO, concen trations in the fermenting wort, confirmed these results for their specific yeast strain. The experiments described in this paper were carried out to study the sensitivity of different brewing yeast strains to CO, inhibition and to determine whether sensitivity to CO2 was related to the oxygen demand of the yeast strain.

Fermenting in an agitated/ stirred wort to release the dissolved co2 shortens fermentation time.

Improved fermentation performance has been reported due to agitation/stirring of fermenting wort19-32-36, trub addition33 and the addition of protein-based yeast foods15. Improved yeast growth and faster attenuation rate were demonstrated under these conditions. These effects were attributed, in most in stances1519-3233, to lowering of dissolved CO2 during ferment ation. The results of this study have also demonstrated improved fermentation performance due to lowering of dissolved CO2 during fermentation for range of brewing yeast strains. There have been varying reports in the literature on the effects of an applied top pressure of CO2 on fermentation rate. Rice el al.31, Nielsen el al.22 and Knatchbull and Slaughter14 reported little if any effect on fermentation rate. Kumada et al.17 showed that both the rate and extent of attenuation were adversely affected by CO2 for fermentations conducted at 9°C under atm of CO2 pressure relative to control with no CO2 pressure. Arcay-Ledezma and Slaughter2 reported slower fermentation rate with CO2 pressure, but suggested that this was result of reduced yeast growth.
Full article here. https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1992.tb01100.x

 

[malt and barley blues]

So in reading that, the yeast won't grow, making the fermentation slow, so is pressurised fermentation worth while?

 

[wide eyed and legless]

So in reading that, the yeast won't grow, making the fermentation slow, so is pressurised fermentation worth while?

I think I could say this until I am blue in the face, closed vessel fermentation is good if done as it was first mentioned by Terri Fahrendorf a brewer who put forward an idea for home brewers to carbonate their beers by applying pressure to the end of fermentation. Over a million posts on homebrew talk led to a misconception of pressure fermenting.

 

[keine_ahnung]

I think I could say this until I am blue in the face, closed vessel fermentation is good if done as it was first mentioned by Terri Fahrendorf a brewer who put forward an idea for home brewers to carbonate their beers by applying pressure to the end of fermentation. Over a million posts on homebrew talk led to a misconception of pressure fermenting.

Thank you Wide Eyed!!!
Good to know where this misconception has come from.

I've mentioned this before, but the only reason I've ever heard of breweries (and I'm talking, established, successful breweries with laboratories that continually control things like diacetyl, acetealdehyd, and all other relevant bi-products in the fermentation) doing this, is a cheat to try and reduce the negative affects of fermenting so warm (i.e. fast!).

In a non-commercial setting, I'm yet to hear any viable tested theory as to why anyone would want to do it.
As soon as one reads up on how yeast actually works, it's pretty clear that putting it under pressure is just undue stress. It's a living microorganism. The whole point of fermentation is that it reproduces and metabolises....similar to us! And we certainly wouldn't like having to do that at 2bar.

There are even breweries in this part of the world that deliberately have massive horizontal tanks, instead of vertical, to minimise the pressure on the yeast at the bottom of the tank. And they do this deliberately, despite it being considerably more expensive (every square metre = $$$).

The technique of closing the fermentation vessel toward the end of fermentation is based on the fine logic of:
- the yeast produces CO2 during the fermentation.
- we want CO2 in the beer at the end
- it's kinda illogical to let all the naturally produced CO2 from the yeast leave the beer, only to pump bought CO2 back into it a few days later....
In this technique the rule of thumb is you close the vessel at around 80% attenuation, then by the time it's finished, you've gradually reached your carbonation pressure (depending on temp of course. -> CO2 solubility is a function of temp).

However this is a very different story to fermenting under pressure.


I'm completely with you on this Wide Eyed. Hopefully we can stop having to go blue in the face sooner rather than later

 

[MHB]

100% Agree - WAFTAM
Bunging (closing the fermenter) has been around longer than bottled CO2, it was the only practical way to get fizz into beer in containers bigger than bottles - especially if you wanted to keep the beer bright and clear. Bunging really started coming into its own around the time of Josef Groll and the first commercial Pilsners, coincidentally the availability of inexpensive clear drinking glasses happened around the same time.
Even the name of the process, comes from hammering the shive into a wooden barrel, so lets say its hardly a new idea.

There is some thought that pressure maturation can be slightly faster, Kunze references the process as a way to speed up Lager production.
Pressure is applied about halfway through the ferment, with faster hotter ferments (<20oC) its possible to speed up lager production to say 17-20 days.
How we got from there to what is being said about pressure fermentation in the home brew community is beyond me.
Mark

Just lookin back over the thread, if one of your reasons for pressure fermentation is the noise, you can get silent airlocks.
Here is one in action on You Tube, might be a better option.
Called a Silent or 3 Piece Airlock
M

 

[MHB]

Just went and had a look at the base recipe, it calls for an OG of 1.063, finishing at 1.018 for an apparent attenuation of just over 71%, you started at 1.048 so finishing at 1.018 isn't likely, after a 90 minute at 62oC I would be expecting closer to 1.000.
Have a long hard look at your mash temperature - for about the millionth time do you have a good glass lab thermometer you use as a reference?
Mark

 

[malt and barley blues]

So I should take it that pressure fermenting is not what it is meant to be.

 

[wide eyed and legless]

So I should take it that pressure fermenting is not what it is meant to be.

What I have read on forums about pressure fermenting reminds me of an old proverb, 'In the valley of the blind the one eyed man is king'
Do some research, there is plenty of real information out there, and don't just take yeast to be an ingredient, as keine_ahnung has stated it is a living microorganism so a good thing would be to read up on yeast and the stresses of yeast.

 

[krz]

.....
Have a long hard look at your mash temperature - for about the millionth time do you have a good glass lab thermometer you use as a reference?
Mark

I have been using the inbuilt temperature gauge on the Guten, but I do have a Thermapen that I used last weekend on another brew, the temperature of the Guten is accurate.

 

[krz]

What I have read on forums about pressure fermenting reminds me of an old proverb, 'In the valley of the blind the one eyed man is king'
Do some research, there is plenty of real information out there, and don't just take yeast to be an ingredient, as keine_ahnung has stated it is a living microorganism so a good thing would be to read up on yeast and the stresses of yeast.

The jury is still is still out, on this.
Your quoted reference is quite old (1992), a lot has changed since then.
It is now quite affordable to purchase pressurised fermenting equipment, so more brewers are experimenting.

There are a lot of reports from people stating that pressure fermenting is producing better tasting beers and some commercial breweries use it.
WilliamsWarn <- "Brewing under pressure, whether it is with extract or all grain enables beer to be fermented faster, more consistently, reduces risk of infection, enables complete carbonation control and increases beer quality"


Many labs conclude that pressure reduces the formation of esters and fusel alcohol,
Good podcast Chris White/Brad Smith/John Blichmann - "european brewers teach this (pressurised fermentation) as a technique ... produced a lager much faster and does work - Chris White"


Until then, because I can (I have a SS Unitank), I will continue my experiments with both pressurised and non-pressurised.
I expect some yeast wont cope particularly well, so I will adjust accordingly.