Fermentation with a long tail

[Agentgonzo]

Does anyone else get fermentation profiles like this?

Fermentation drops with a normal profile and "almost finishes" but then has a long tail where it gradually drops the last few SG points over a week or two - rather than just finishing and staying at a stable SG. I have this sometimes (every time I use M21) but this one is with CML Belgian.

 

[MashBag]

Nutrition or pH swing would be my first though?

What is the water profile?

 

[marshbrewer]

So, this is where I show my ignorance, but while I don't have a tilt or similar to monitor SG constantly, I always seem to get this and assumed it was normal?

 

[Agentgonzo]

Nutrition or pH swing would be my first though?

What is the water profile?

Very hard. ~300ppm hardness.

So, this is where I show my ignorance, but while I don't have a tilt or similar to monitor SG constantly, I always seem to get this and assumed it was normal?

That's what I'm not sure about. Having seen a lot of graphs on the internet, once they start to bottom out, they go pretty flat, rather than taking a week to finish the last few points.

 

[MashBag]

Typically I would test pH now, I think it's out and ½ tsp bicarb will fix.

If no eggy smell (nitrogen) and the pH is OK.
½ DWB for calcium et Al.

Oyster shell or chicken grit will also fix.

 

[MashBag]

Very hard. ~300ppm hardness

Do you correct this?

 

[Agentgonzo]

Do you correct this?

Yes. 6ml of 80% lactic acid in the mash, another 2 in the spage.

(I never used to adjust for hardness until about 3 years ago. Local microbrewer I talked to (same water supply) uses the equivalent of 2ml in the mash as opposed to my 6)

pH was at 5.4 during the mash. I didn't measure it after that (never do). No eggy smell (which I thought was sulphur not nitrogen)

 

[MashBag]

OK. Double check your acid addition. I prefer AMS, BUT you need to use the alkanity figure not the h#rdn3ss. I wrote it is code, 'cos "that" word it can trigger some people

The pH can swing during fermentation and create a stall... Test it when it is stalled.

Yes eggy smell is sulphur indicating a lack of nitrogen. So a proprietary nutrient should be used (and a bit of copper pipe)

 

[Agentgonzo]

BUT you need to use the alkanity figure not the h#rdn3ss. I wrote it is code, 'cos "that" word it can trigger some people

I've never understood the difference between alkalinity and hardness given that they are both measured in the same way, tend to be highly linked (high hardness goes with high alkalinity) and the same ions in the water contribute to both

 

[Agentgonzo]

I'm away at the moment so can't test pH, but will take a look at it when I get back or on a subsequent brew. Thanks.

Definitely no eggy smell. The beers always turn out fantastic anyway, so not really concerned. Just interested at an academic understanding.

 

[Agentgonzo]

The pH can swing during fermentation and create a stall... Test it when it is stalled

Well it's at 82% attenuation at the moment, so pretty sure it's finishing, not stalling!

 

[Stu's Brews]

The rate of fermentation slowing down towards the end is pretty normal (within reason).

As the amount of fermentable sugar available to the yeast begins to dwindle, the cells start going to sleep and flocculating.

Some yeast strains are more sensitive to this than others (looking at you London Ale III...) and benefit from the temperature being raised towards the end of fermentation to help them finish up.

If you have a VERY long tail (i.e. up to a week) then it's probably more likely to be a yeast health or pitching rate issue.

 

[matt76]

It looks perfectly normal to me (based on my own Tilt logs);

- Ramps up over the first 24hrs or so
- Goes like the clappers for another 2-3 days
- Then tails off to within a few points (1-3 maybe?) of the eventual FG
- Might drop another point or so within the first week since pitching
- From here I would typically leave my beers for 2 weeks in total from pitching before I package, give or take a few days either way (probably not less than 10 days). It might drop another point or so in that second week

My feeling is that second week is giving the yeast time to clean up any diacetyl etc, especially if I've dry hopped.

(For lagers fermented at cold temperatures you can pretty much double all those timescales)

What are you expecting to see?

 

[MashBag]

Well it's at 82% attenuation at the moment, so pretty sure it's finishing, not stalling!

Sorry, I missed your point.

That looked like a stall to me. I bottle at day seven and never see anything like that with beer.

 

[MashBag]

If you have a VERY long tail (i.e. up to a week) then it's probably more likely to be a yeast health or pitching rate issue.

I do like your pitch rate suggestion

 

[Agentgonzo]

That looked like a stall to me. I

So what does "a stall" look like,, as opposed to "the end of fermentation"

 

[Agentgonzo]

Yeast was a full sachet of (rehydrated) CML yeast - well within it's best before date into nicely aerated wort

 

[Agentgonzo]

What are you expecting to see?

Roughly the same thing as the graph I posted, but flattening out and remaining flat at the end rather than continuing to decline slowly

 

[Stu's Brews]

Roughly the same thing as the graph I posted, but flattening out and remaining flat at the end rather than continuing to decline slowly

I think that graph looks about right to me.

You've got roughly 12 hours lag time, then 2 days of rapid fermentation during the yeast growth phase and then a couple of days where everything is slowing down as the yeast runs out of sugars to consume.

I'd only be concerned if that downward trend was continuing for another 4 or 5 days.

What is your expected final gravity?

 

[Agentgonzo]

What is your expected final gravity?

No idea. Each brew is different. But it's roughly looking like what I'd expect (82% attenuation at the moment)