M21 stuck fermentation?

[GregoireM]

Hello all. Still a beginner, I am faced for the first time with something that could be stuck fermentation, and would like to get advised from more experienced people. Here is the situation:

Brewed 8L of ale split into 2 demi johns.
0.5kg of Pilsner malt
0.5kg of Wheat malt
mash for 1h40 at 65C
200g of honey 10 minutes before end of boil
orange zest and cinamon in boil and fermenter

OG with all that: 1.034 (quite low I know... but miscalculated my malt amount and decided to try and ferment it anyway)

Pitched half a pack of Mangrove Jack M21 in each demi john on 4L of wort. Wort was probably around 30-35C when I pitched. Reduced temperature to around 18 in water bath afterwards.

Started nicely overnight, and continued bubbling (but less than my previous batches) for 2 days, and now no activity at all. Krausen disappeared. I raised temperature to 21C, but still stuck, might try to raise to 25 as this is the limit of the yeast, but don't want off flavours either.

I know a few stuff were not ideal:
-too little malt, therefore low OG (I aimed for 1.045)
-picthed too high? not rehydrated?
-not enough oxygen? (I didn't really actively aerate the wort, but never did so with M84 yeast in my previous batches and had no problem)


What do you think happened? After reading around, I think of a few thing that could've happened, but don't know if it's true:
- I killed most of the yest by picthing too high, th elittle that survived did half the job but there wasn't enough viable cells to finish it?
-there was too little malt and therefore not enough nutrients?
- there was not enough oxygen?
- something else? the yeast needs more oxygen or something else than M84, therefore why I didn't have problem before?

If nothing happens in the next day, I'll take another hydrometer reading, but I don't want to risk infection and waste too many samples as it is already a small batch.

 

[AlexKay]

It sounds like you're done, not stuck. I've done single hydrometer readings on small batches; just let it sit for a good long while (two or three weeks total) before bottling.

 

[hotbeer]

There are times I have to look very very close to see any activity in the ferment. Sometimes with a flashlight and then zoom in with my phone.

And if activity to you is bubbling in the airlock, then just stop right there. Don't use the airlock to gauge activity.

I have even had some ferments seem to stop, but weeks later they start bubbling like a fine champagne.

So be patient, something probably is going on even if it doesn't appear to be. Don't be opening the fermenter up to check on things. You'll only let oxygen in which you don't want getting in there. Wait at least the time the recipe states before even checking with a hydrometer. And even then let it go longer till it clears up some if it's too cloudy.

Patience......

 

[dmtaylor]

M21 is a fussy yeast. Just leave it alone for like 3 more weeks. It will turn out fine. Don't heat it up. Don't do anything. Just leave it alone.

 

[Protos]

With M21, I've had some really weird fermentations.
I bottle most of my medium strength beers after 3 weeks in primary, and with M21 I almost always got overcarbed gushers.
So with my last M21 beer, I decided to keep it in primary for longer to see why the previous beers were overcarbed. And what I saw after 10 days of reaching stable FG, was a sudden resumed fermentation. And quite an active one: it produced the second layer of flocculated yeast in my carboy. I wonder if M21 is actually a blend of two yeast strains.

Now I think my standard 3 weeks in primary weren't enough for this yeast.
Next time I'll keep my M21 Wit in primary for 7 days and then rack it to secondary for whatever it takes it to complete its fermentation and re-fermentation.

 

[GregoireM]

Thanks all for your answers, I also gathered other information from other threads on this forum, and it seems the few days of active fermentation, followed by a pause and another fermentation is a recuring feature of this yeast...

Glad I asked before doing anything, I will leave it alone at 20.5C. Although I'd be tempted to rack it to a secondary fermenter... I'm pretty sure the risk of oxygenation through syphoning is greater than the risk of off flavour from 3-4weeks of autolysis.

I'll let you know in a few weeks how it turned out. I wish Mangrove Jacks had better information available about their yeasts.

 

[RM-MN]

Glad I asked before doing anything, I will leave it alone at 20.5C. Although I'd be tempted to rack it to a secondary fermenter... I'm pretty sure the risk of oxygenation through syphoning is greater than the risk of off flavour from 3-4weeks of autolysis.

Yeast don't normally die and decompose in your beer. Autolysis risk is extremely low in the quantities of beer that homebrewers brew. Oxidation is a much, much higher risk. You can leave your beer in the primary fermenter for a couple months without autolysis.

 

[RM-MN]

Now I think my standard 3 weeks in primary weren't enough for this yeast.
Next time I'll keep my M21 Wit in primary for 7 days and then rack it to secondary for whatever it takes it to complete its fermentation and re-fermentation.

If your beer isn't done with fermentation why would you separate it from the bulk of the yeast? That is what you do when you rack to secondary.

 

[Protos]

That's because I always try to avoid leaving beer on the lees for longer than 4 weeks..
I know that at the homebrewer's scale there's no much concern about autolysis. OK, let's not call that autolysis, but some things definitely happen in an old yeast cake, and I've learned by experience they aren't always for better, especially in warmer season. It's not about infection or something, just about subtle (but noticeable) flavour changes.

And what about separating the beer from the yeast, well, M21 is a low-flocculent yeast, so even after 2 weeks in primary there's a lot of cells in suspension, totally enough to complete the second fermentation burst. Generally, I rarely rack to secondary, as I rarely keep beer in fermenter for longer than a month. And it seems this yeast might require some more time than 4 weeks.

 

[dmtaylor]

Glad I asked before doing anything, I will leave it alone at 20.5C. Although I'd be tempted to rack it to a secondary fermenter... I'm pretty sure the risk of oxygenation through syphoning is greater than the risk of off flavour from 3-4weeks of autolysis.

I'll let you know in a few weeks how it turned out. I wish Mangrove Jacks had better information available about their yeasts.

Don't rack it. The risk of autolysis within 4 weeks is about zero. In my experience, autolysis begins after more like ~9 weeks.

Mangrove Jack doesn't actually make their own yeast, hence their limited sharing of knowledge of it. They can only copy/paste and wordsmith input from the actual yeast manufacturer(s).

 

[hotbeer]

Thanks all for your answers, I also gathered other information from other threads on this forum, and it seems the few days of active fermentation, followed by a pause and another fermentation is a recuring feature of this yeast...

Glad I asked before doing anything, I will leave it alone at 20.5C. Although I'd be tempted to rack it to a secondary fermenter... I'm pretty sure the risk of oxygenation through syphoning is greater than the risk of off flavour from 3-4weeks of autolysis.

I'll let you know in a few weeks how it turned out. I wish Mangrove Jacks had better information available about their yeasts.

The beer I've been most disappointed with it's flavor is the one and only beer I racked to a secondary. Actually this is the only beer I'm disappointed with it's flavor.

I do have another that I'm even more disappointed with, but not it's flavor, it's that I over carbonated it and every bottle is a volcano.... but a good tasting volcano.

 

[GregoireM]

I'm really the kind of person that wants to see by himself, and racking or not seems to be a divisive subject. I have split my batch into 2 demi johns, so I think the best way to know if it could make a difference is to rack one and leave one alone, and i'll see by myself if one is better than the other!

 

[Miraculix]

I'm really the kind of person that wants to see by himself, and racking or not seems to be a divisive subject. I have split my batch into 2 demi johns, so I think the best way to know if it could make a difference is to rack one and leave one alone, and i'll see by myself if one is better than the other!

Only If they are completely separate batches and then you wouldn't know if a difference is caused by the racking or by something else.

 

[GregoireM]

Everything else is the exact same, just 8L split into 2 demi johns