Fermentation Slow to Finish

[ncbrewer]

My latest batch didn't ferment as usual. It was an extract batch with 50/50 Pilsner and Munich malt. I typically take a gravity reading after 15 to 20 days, and again two days later. It's always stable, and I bottle. On the last batch, I sampled at 18 days - 1.0148 and hazy. Checked again at 20 days - 1.0139 (down 0.0009) and still hazy. I waited and checked again today - 26 days (had bronchitis, so waited a little longer than intended). Gravity was 1.0132 (down by another 0.0007), but clear, so I feel that it's probably finished. Plan to check again in another three days.

Process description:

Yeast: Mangrove Jack's M54
Yeast was rehydrated at 81F in boiled and cooled tap water
Used bottling hydrometer with 0.0005 graduations - can easily read to nearest 0.00025
Pitching temp 65F
Active fermentation temp - 67F (four days)
Fermentation temp after active - 70F
Checked hydrometer calibration - good
Gravity numbers are corrected for temperature, but there was very little difference in temperatures of the various samples
4.9 gallons to fermenter
OG 1.055

The only thing different than my normal process is the M54 yeast - I haven't used it before. But I've read many posts on here about it being a perfectly good yeast.

I don't see much question about how to proceed. I'll check gravity again in a few days and bottle when it's stable. But I was really surprised by this fermentation and would like to see what others make of it. It's probably one of those things that just isn't always predictable.

 

[IslandLizard]

Did you decarbonate your samples before taking a reading? That could explain the slight dropping.

Otherwise, some yeasts may take a longer time finishing up by digesting some of the larger sugars (e.g., maltotriose). The Munich extract may contain some of those.

 

[ncbrewer]

Did you decarbonate your samples before taking a reading? That could explain the slight dropping.

Otherwise, some yeasts may take a longer time finishing up by digesting some of the larger sugars (e.g., maltotriose). The Munich extract may contain some of those.

Yes, I pour the sample from one glass to another 20 times and dip the foam off to release the CO2. It makes a small but measurable difference.

I've used the same extract many times and never seen this before.

 

[IslandLizard]

The yeast is the only difference left over, then. Maybe she's gnawing on some of those larger sugars.

 

[IslandLizard]

Now I never measure or record the 4th decimal in gravity readings. I don't even own a precision final gravity hydrometer.

In your case I would only see and record 1.015, 1.014, and 1.013 over those days. My conclusion would be the same as yours, yeah, it's still slowly attenuating.

 

[ncbrewer]

The yeast is the only difference left over, then. Maybe she's gnawing on some of those larger sugars.

It does look like the yeast is the only difference, but it could be something other than the strain. It was in my refrigerator while I had it, but maybe it was exposed to heat somewhere? Yeast seem to have a mind of their own and don't always do what we expect. I'll bet I could repeat this with another batch and get stable gravity in two weeks.

Lots of brewers have been reporting on this yeast strain in the "Warm Fermented Lager" thread. I'll ask if anybody else has experienced slow fermentation.

 

[dreaded_rust]

Think I'm with IslandLizard here.
Over the course of 8 days your gravity dropped a smidge. I would figure with that temp and amount of time it would be well past finnished up. I'd venture to say its gotta just be a slow yeast.

 

[ncbrewer]

Update: After 29 days gravity was stable and it was clear. I bottled it. That's really slow. If I use this yeast again, I'll be on the look-out for a slow finish.

I asked about this yeast being slow in the Warm Fermented Lager Thread (https://www.homebrewtalk.com/forum/threads/warm-fermented-lager-thread.592169/page-21), but didn't get any more input. I searched the whole thread and found one mention of it being slow, but that finished in 11 days (Post #816). I would have felt great about 11 days. So maybe it's a slow yeast, or maybe I made a mistake somewhere, or maybe it's just yeast not following a calendar. Either way, thanks for the input.

 

[ListerH]

My first instinct as with the above was that it was just taking its time to finish up. I have used M54 before and when I check my records, it was a full 35 days til I was confident it was done.

Just a thought... and I have never really thought about this before, but could the fact that yeast slowly drops out of suspension also account for very small movements in gravity?

 

[day_trippr]

35 days?!
"Ain't nobody got time for dat!"

 

[Vale71]

My first instinct as with the above was that it was just taking its time to finish up. I have used M54 before and when I check my records, it was a full 35 days til I was confident it was done.

Just a thought... and I have never really thought about this before, but could the fact that yeast slowly drops out of suspension also account for very small movements in gravity?

Just like your body when you're taking a bath smaller particles is suspension will not change the gravity of a solution.

 

[ncbrewer]

I have used M54 before and when I check my records, it was a full 35 days til I was confident it was done.

Wow. Even slower than mine.

 

[ncbrewer]

Some follow-up on this - this email correspondence with Mangrove Jack's sums it up and includes a second batch with M54:

ME: I tried M54 for the first time a few months ago. Fermentation was very slow. It was an extract batch with 50/50 Pilsner and Munich malt. I typically take a gravity reading after 15 to 20 days, and again two days later. It's always stable, and I bottle. On the M54 batch I took the following gravity samples:

18 days - 1.0148 and hazy.
20 days - 1.0139 (down 0.0009) and still hazy.
26 days - 1.0132 (down by another 0.0007), but clear
29 days - 1.0129 and clear. Bottled.

Process description:
Yeast: Mangrove Jack's M54. One pouch, used 21 months before expiration date.
Yeast was rehydrated at 81F in boiled and cooled tap water
Used bottling hydrometer with 0.0005 graduations - can easily read to nearest 0.00025
Pitching temp 65F
Lag time was normal (bubbling the next morning)
Active fermentation temp - 67F (four days)
Fermentation temp after active - 70F
Checked hydrometer calibration - good
Gravity numbers are corrected for temperature, but there was very little difference in temperatures of the various samples
4.9 gallons to fermenter
OG 1.055
Samples were decarbonated before reading the gravity

The only thing different than my normal process is the M54 yeast.

I thought what I experienced was a fluke and tried it again in my latest batch. Fermentation was very slow again - 40 days total, with five gravity samples.

Are there any known issues that would explain the slow fermentation with this yeast? Maybe something inherent in the strain, or exposure to heat at some point? I wondered about rehydration temperature since the instructions don't discuss the California Lager Yeast fermented at ale temperatures. But I expect that rehydrating at 81F should be fine - ?

Any help would be appreciated.

MJ: No known issue with M54, confirming he used 1 re hydrated pack for the the 4.9 gal.

Assuming this was a fresh pack and not had poor transport between us and the customer. Our yeast contain at least 5x10^9 viable cells per gram, this means there are at least 5x10^10 viable cells per pack, but normally you are looking at 200 billion cells per pack.

For a ‘lager’ you should be using 1.5 million cells per ml per degress plato

For 18548ml (4.9 gals) of lager at 13.5 plato (1.055 SG) = 3.76x10^11 cells of yeast for this beer

3.76x10^11 cells / 200 billion cells per pack = 1.88 packs of yeast for this brew

Therefore I would expect that the ferment was a bit sluggish based on one pack

ME: Thanks very much for the considered response - impressive considering the number of users of Mangrove Jack's yeast. You discussed pitch rate for lagers, but I was under the impression that a lager yeast pitched and fermented at ale temperatures would normally be pitched at the ale yeast rate - lots of brewers do this. I couldn't find any instructions on the website concerning rehydration temperature or pitching rate for this yeast/temperature combination. Do you know if this has been tested or just an assumption?

MJ: Here is a link to rehydration information you are after
https://cdn.shopify.com/s/files/1/0...68-8d16-673b5fb84f75.pdf?16489226078703376035

ME: Thanks for that. But the pitching rate information covers two alternatives: 1) Ales and 2) “Lagers to be fermented at 14°C (57°F) or lower”. There is no mention of lager yeast pitched and fermented at ale temperatures. Based on what I've read and what the tech data seems to imply, it seems that the ale pitching rate would apply when lager yeast is used at ale temperatures. Is it possible this has never been tested?

MJ: Our tech team have advised that this is a hybrid strain that is classed as a lager strain regardless of temperature, and the aim is a clean fermentation profile. Therefore, the pitching rate also needs to ensure that the yeast are under the least amount of stress possible. As a result, the lager pitching rate is applied rather than the ale.