Stuck Fermentation

[mancer62]

My Woodfordes Wherry seems to be stuck around 1018 from an OG of 1040 made 11 days ago.
My Wilko IPA made on the same day and with an identical OG 1040 is now at 1008. Would the first line of attack be a simple stir to try get it restarted?
If so would u vigirously stir all the trub at the bottom or just stir the beer avoiding the trub?

 

[terrym]

Your Wherry is in a long line line of stuck fermentations. Basically although the yeast is fine there isn't enough of it provided with the kit.
Usual advice for restarting stuck fermentations is any or all of these
- rouse the yeast by either gently swirling the FV with the lid on or gently stir with sanitised spoon avoiding pulling any air in
- raise the temperature, say up to 22*C
- make up a concentated solution of sugar solution with 100g sugar using boiling water allow to cool and add that
You could try new yeast (e.g Wilko ale yeast) but at 1.018 you might struggle to get things going again.
Finally if you brew a Wherry again substitute the yeast (e.g use Wilko ale yeast) but save it and use for the next Muntons kit you do where there is only a 6g packet so you can double up the yeast quantity.

 

[mancer62]

Ty for replies. When stirring with sanatised spoon. Would I give it a good stir disturbing all the yeast on the bottom to mix in with the beer on top?

 

[terrym]

Ty for replies. When stirring with sanatised spoon. Would I give it a good stir disturbing all the yeast on the bottom to mix in with the beer on top?

Yes but try not to splash or entrain air into the liquid as you stir.
If you get it going again there should be plenty of time for the yeast to resettle.
And in any case you should be leaving it long enough in the FV so that you package clear or nearly clear beer.

 

[Dutto]

I understand that there are normally only two reasons for a brew to get "stuck" after it has started the fermentation process:

1. The alcohol level has risen to a level where the yeast has effectively killed itself.

2. The yeast has run out of oxygen in the wort and therefore can't complete the normal process of changing sugar into alcohol and CO2.

I understand that 1. is very rare in beer brewing but can occur with wines if the yeast has an alcohol tolerance that is lower than that required for complete fermentation of the wine.

With regard to 2. I once saw a recommendation that for a "stuck" brew one should "Beat it as if it owed you money." in order to introduce oxygen into the wort. I use this method myself and also add additional yeast. So far, the brew has always restarted and I have had no infections. The lack of infections I believe comes from the fact that the wort is already "nearly beer" and therefore has an alcohol content that can resist infection.

To try and prevent a brew from "sticking", I try to introduce oxygen to a kit wort by "blasting" in any water used to dilute/cool the kit; and for an AG wort adding a yeast nutrient and stirring it vigorously when it is being cooled. These methods work 99% of the time.

An alternative measure (one that I have avoided) is to introduce oxygen to the wort by means of an aquarium pump and a "stone". It seems a logical system but I have avoided it because it could introduce another source of infection.

Hope this helps. :thumb:

PS

A third reason for a brew to have a high FG is the presence of non-fermentable sugars. In this case the brew hasn't "stuck" because all of the fermentable sugars have been dealt with and you finish up with a sweeter brew. It doesn't happen with a Wherry Kit.

 

[Sadfield]

Ooops! Stupid phone.

 

[Sadfield]

I understand that there are normally only two reasons for a brew to get "stuck" after it has started the fermentation process:

1. The alcohol level has risen to a level where the yeast has effectively killed itself.

2. The yeast has run out of oxygen in the wort and therefore can't complete the normal process of changing sugar into alcohol and CO2.

I understand that 1. is very rare in beer brewing but can occur with wines if the yeast has an alcohol tolerance that is lower than that required for complete fermentation of the wine.

With regard to 2. I once saw a recommendation that for a "stuck" brew one should "Beat it as if it owed you money." in order to introduce oxygen into the wort. I use this method myself and also add additional yeast. So far, the brew has always restarted and I have had no infections. The lack of infections I believe comes from the fact that the wort is already "nearly beer" and therefore has an alcohol content that can resist infection.

To try and prevent a brew from "sticking", I try to introduce oxygen to a kit wort by "blasting" in any water used to dilute/cool the kit; and for an AG wort adding a yeast nutrient and stirring it vigorously when it is being cooled. These methods work 99% of the time.

An alternative measure (one that I have avoided) is to introduce oxygen to the wort by means of an aquarium pump and a "stone". It seems a logical system but I have avoided it because it could introduce another source of infection.

Hope this helps. :thumb:

PS

A third reason for a brew to have a high FG is the presence of non-fermentable sugars. In this case the brew hasn't "stuck" because all of the fermentable sugars have been dealt with and you finish up with a sweeter brew. It doesn't happen with a Wherry Kit.

1) Surely, if a yeast can't tolerate the lower alcohol levels of an incomplete attenuation, it would never have able to do the job anyway, and so shouldn't have been used? Is it not decreasing pH, acid tolerance that halts yeast performance, sending it into a dormant state? If alcohol kills yeast, how can we repitch yeast in a new fermentation?

2) Almost correct. Oxygen is needed for cell reproduction and growth. Poor yeast health and cell count will cause a stuck fermentation. However Glycolysis, is an*anaerobic*process, yeast are unable to carry out*aerobic respiration and will automatically move into a type of*anaerobic*respiration called*alcoholic fermentation.

Same advice though, oxygenate well and pitch the correct amount of yeast, to avoid stuck fermentations.

Sent from my E5823 using Tapatalk

 

[Scotbrew]

PS

A third reason for a brew to have a high FG is the presence of non-fermentable sugars. In this case the brew hasn't "stuck" because all of the fermentable sugars have been dealt with and you finish up with a sweeter brew. It doesn't happen with a Wherry Kit.

I've got a similar stopped at 1018 and as I used brewing sugar rather that ordinary granular stuff suspect that the yeast has converted all it can. Guess I'll give it a taste test and decide if I should bother bottling. A side question, apologies if this hyjacks the thread, how much sugar should I dilute to add to 25ltr to batch prime?

 

[Clint]

One thing that puzzles me...
It's said that the wort should be aerated as the yeast needs oxygen and that (particularly during any boiling if done) oxygen is driven off and should be replaced with poring the wort from height,thrashing it up,air stone or whatever.
I understand "water" is H20....ie 2 of hydrogen and 1 of oxygen. ..so if the wort is low or oxygen depleted what exactly is left in the pan? Just the H?

 

[terrym]

I've got a similar stopped at 1018 and as I used brewing sugar rather that ordinary granular stuff suspect that the yeast has converted all it can. Guess I'll give it a taste test and decide if I should bother bottling.

It makes little difference whether you use brewing sugar or table sugar, they should both fully ferment out, although the yeast cells will find it a little harder with table sugar because there is an intermediate step in between sucrose to ethyl alcohol, but in practical terms you don't notice it.
Assuming you did not start at a very high OG, the reason your brew has stopped at 1.018 is given above, which, if its a Wherry, is most likely to be insufficient yeast in the kit packet.
If its a kit and you used tap water it is likely that there was enough dissolved oxygen in the water to initially grow healthy yeast cells. The only time you really need to spend time beating to get oxygen in the wort is for AG or full extract brewing where the wort contains no oxygen since you have boiled it out of solution. And even then there is only so much you can do, because oxygen is not very soluble in wort or water.

 

[Clint]

...but oxygen is a component of water....
After a quick Google apparently you can get the dissolved oxygen out of water by boiling under pressure and continuous flushing with nitrogen. ....

 

[terrym]

...but oxygen is a component of water....
After a quick Google apparently you can get the dissolved oxygen out of water by boiling under pressure and continuous flushing with nitrogen. ....

If you mean that oxygen is a chemical component of water that's correct. Oxygen and hydrogen are chemically bonded to form water, which is usually very stable in all phases.
However dissolved oxygen is different. Oxygen is not very soluble in aqueous solutions because it doesn't react, so in practical terms its a physical not a chemical thing. Nitrogen is the same. Carbon dioxide on the other hand is different since it reacts to form a weak chemical bond with water as carbonic acid, and so water will 'absorb' more CO2 than O2.
In short some gases are not very soluble because they don't react, whereas others are soluble because they do react. And in the latter some chemical bonds are stronger than others.
And for dissolved gases, without chemical reaction, temperature and pressure will alter the equilibrium as you have noted.

 

[foxbat]

One thing that puzzles me...
It's said that the wort should be aerated as the yeast needs oxygen and that (particularly during any boiling if done) oxygen is driven off and should be replaced with poring the wort from height,thrashing it up,air stone or whatever.
I understand "water" is H20....ie 2 of hydrogen and 1 of oxygen. ..so if the wort is low or oxygen depleted what exactly is left in the pan? Just the H?

Aerated wort, and water, has O2 molecules trapped in the gaps between the larger molecules that make up the wort itself. Boiling tends to drive off these 'free oxygen' molecules into the atmosphere.

Aerating is an attempt to encourage free O2 from the atmosphere to get trapped again between the larger wort molecules ready for the yeast to consume.

 

[Clint]

Thanks for the replies! It's a good job we have people who don't mind getting their heads blagged by the less informed!!

 

[mancer62]

so do I stir for say 30 secs to 1min or so including the trub ? ty

 

[mancer62]

that's what I have just gone ahead and done lol

 

[Dutto]

......... oxygen is not very soluble in wort or water.

Er ... oxygen is very soluble in cold water when compared to nitrogen, which is the most common gas in air. Extracting oxygen from the water is how fish and most other forms of water based life manages survive.

If you stick a pan full of water on a cooker ring and start to heat it up you will see, well before the water reaches boiling point, small bubbles on the bottom of the pan. They are bubbles of oxygen that is being being driven out of the water as the water in the pan heats up.

Oxygen depletion will happen in any wort that has been heated which is why with AG brewing the wort needs oxygenating after it has been boiled. With a kit, the same thing can happen if the water added to the brew has been heated.

The yeast provided in a kit is often a bit past its "Use By" date. If the yeast has died then the fermentation process will not start, however this is very rare and with old yeast it can take quite a time for a brew to get going.

However, after a slow start and given enough sugar and oxygen the yeast will reproduce until such time as the sugar is consumed OR the oxygen is depleted OR the ABV reaches a point that the yeast cannot tolerate and dies. The yeast (both dead and live cells) forms the trub at the bottom of the FV after fermentation is completed. (The fact that there are plenty of live cells in the trub is proved by using it to make bread instead of throwing it away. It imparts a lovely flavour. :thumb:)

The reason we make a Yeast Starter in brewing is so that we know that there are a sufficient number of yeast cells present to start a brew immediately that the yeast is pitched. This speeds up the fermentation process and reduces the time when the wort is open to infection.

Hope this helps. :thumb:

 

[Sadfield]

There is a reason why non-distilled beverages are no stronger than 12-15%, this is the limit of the yeast tolerance to alcohol. They are tolerant to levels of alcohol that will kill bacteria that compete for the same sugars, and will happily ferment as long as they stay in suspension.

Stuck fermentation is a result of not having enough healthy yeast cells. As a result the yeast can flocculate to the bottom before all the sugar is consumed. Yeast will consume the least complex sugars first, which is why gravity drops rapidly with vigorous co2 production then stalls as the yeast drops to the bottom leaving no suspended yeast to consume the more complex sugars.

Ethanol production by yeast will only happen in the absence of oxygen, it is an anaerobic process. Running out of oxygen will not stop fermentation, but start it. Oxygen is used in the initial growth phase. Do not add more oxygen to beer to try to restart a stuck fermentation. Add more yeast and/or carefully rouse the existing yeast back into suspension in the solution. A slight raise in temperature will aid this.

 

[Dutto]

There is a reason why non-distilled beverages are no stronger than 12-15%, this is the limit of the yeast tolerance to alcohol. .............

Er ..... please explain your 12% upper limit v. a Turbo Yeast which will produce a 20% ABV.

https://www.brew2bottle.co.uk/still...MIo6-WgLnZ1wIVirvtCh0Q1ADLEAQYAyABEgJykPD_BwE

Apart from it being a specially bred least the packet apparently also contains nutrients that produce O2.

:thumb: :thumb:

 

[terrym]

Er ... oxygen is very soluble in cold water when compared to nitrogen, which is the most common gas in air.

All things are relative.
From this
https://sites.chem.colostate.edu/di...ference data/solubility of gases in water.pdf
Oxygen is about twice as soluble as nitrogen. But CO2 is about 40 times as soluble as oxygen.
Looking through the table all the gases that react e.g CO2, chlorine, SO2 are far more soluble than those that don't, which is the point I made earlier in this thread.
Anyway as far as aerating wort is concerned I've put forward my opinion earlier on here as did other people, and looking back some of us don't bother with it at all!
http://www.thehomebrewforum.co.uk/showthread.php?t=72959