WLP400 slow in the finish - Malnutrition?

[ASantiago]

Having read the threads about slow WLP400 Belgian Witbier fermentations, I have to unfortunately add my cries over the same thing to the chorus.

I did a starter (*always* do) and the fermentation got going strong within 6-8 hours. Pitched at 68F, increased to 72F over two days. Big krausen, good blow off. That was two weeks ago today.

Today the SG is at 1.018 which, starting at a 1.055, means an apparent attenuation of ~67%. Not horrible, but I was expecting higher. FG was expected at 1.012-014. So it's off by .004-.006. Not exactly the end of the world.

I can *see* fermentation is on-going. Not only am I getting the tell-tale bubbling through the blow-off, but I can see bubbles continuously being produced by the fermentation and stuff moving around in the fermenter. Not an aggressive thing; a bubble every 1.5 seconds or so, now on-going the same way for a week. Considering it's all happening in a temp-controlled environment, I feel safe ruling out degassing.

I'm going to let it do its thing and at some point in time I'm going to stop the fermentation if I have to. I'm not going to pitch anything else in an attempt to bring the SG down.

In the meantime, I'm wondering why this happens. The one thing I can come up with is malnutrition. Why? I use distilled water with mineral adjustments and shot for a calcium content of 50 PPM per some guidelines I got. I'm guessing that's OK for regular, all-barley beers, but for a beer with a grain bill composed of 51% wheat and oats, maybe that's not enough?

Barley contributes yeast nutrients. Do wheat and oats?

The theory killer here is that I *always* add yeast nutrients to the boil. But nonetheless, I do wonder. One of the symptoms of under-fed yeast, if I recall correctly, is slow fermentations.

 

[Quaker]

What temp did you mash at? Was it allowed to cool off a few degrees which might have caused the yeast to drop?

 

[ASantiago]

What temp did you mash at? Was it allowed to cool off a few degrees which might have caused the yeast to drop?

Mash was at 150-152F. It was in a closed cooler, so very little temp loss.

The fermentation started at 68F and I took it to 72F. But in there there are small, 1-2 degree fluctuations in temperature due to the delay in the temp controller.

 

[Quaker]

So mash and ferm temps don't seem to be the problem. What about aeration or oxygenation at pitching? I think with your nutrient addition and the grain bill, you should have been fine for nutrients. I have a vial of WLP400 for a future brew, so I have a vested curiosity in this.

 

[ASantiago]

Right before pitching I stirred the wort in the fermenter with the handle of a long spoon for 10 minutes. Can't say that's sufficient, but it's what I do for every batch and it seems to do the job. This fermentation got going pretty quickly so there's a good chance the aeration was sufficient.

As of this morning (Monday, Aug 20) fermentation is still going. On Saturday, I started my usual temp increase at the end of each fermentation to get the yeast going a little harder right before I start dropping the temp to 38F over the course of several days. I will be keeping the beer at around 75F for a few days (again, it's the end of the fermentation). So, we'll see what happens with that. I'm hoping the higher temp will get the yeast to get to the end of their job and start dropping on their own. Regardless, the process will continue. This baby has to be on tap for Labor Day weekend!

Indeed, this seems to be a yeast to watch. Many others have reported strong initial fermentations followed by a long period of slow continuing fermentation.

 

[greenbirds]

I recently brewed a Belgian Blonde with WLP400. I did a starter, oxygenated with an O2 stone, mashed at 150, raised ferm temp gradually from 66 to 72 during the first 10 days, then to 78 for the remainder.

My primary fermentations are usually complete in 7-10 days, and I keg at 12-21 depending on the beer. This yeast took a full 24 days to attenuate to 1.013, and I let it sit another week just in case, but it didn't drop much if at all. The beer is fantastic.

I do not necessarily buy into the 4+ week primary logic that pervades this forum (as long as your cell count and brewing/fermentation practices are sound; otherwise it may help), but occasionally some yeasts do just take longer.

 

[ASantiago]

By the time I start the cooling down, the beer will be at fermentation temperatures for 18 days. I agree that giving it more time is probably the wise thing to do. But with my supply dwindling and Labor Day around the corner, the extra gravity points will just have to be missed.

I'm not into the minimum days in fermenter philosophy either. I don't rush my beers, but my turn-around is about 3 weeks (give or take), with several days of that used for clarifying at low temps. Professional breweries, and I'm talking about *craft* ones, have shorter turn-arounds than that.

Between the clarification and an addition of gelatin (not used for this Belgian, of course ), I end up with fairly clear and ready to drink beers in 3-4 weeks. This is kegging, not bottling.

But that's a religion wars thing, so to each his own.

 

[ASantiago]

Just an update here: After gradually raising the temperature to 76F last weekend, the SG, which will be the FG, is 1.013 as of today (for an ABV of ~5.5%). This is in line what I was expecting. The Belgian yeast character is there (phenolics, esters), but is a little subdued. This may be due to a healthy pitch, a cooler fermentation (~72F), and the increased temp during the last week or so. I kinda wanted something more assertive in terms of the yeast's contribution, but it will do (besides, what choice is there?). It may be too early to comment on that, however. We'll see what happens after the beer is carbonated.

Given the nutrient I added during the boil and overall pattern of the fermentation, I now don't think the slower latter-fermentation stage this yeast is known for is due to malnutrition. It may just be standard behavior for the yeast (assuming sufficient pitching and oxygenation) and also possibly due to the high percentage of wheat and oats in the grain bill.

Starting today, I'm beginning the cooling period that will gradually take the beer to 38F by next Wednesday, when I plan on kegging it for enjoyment over Labor Day weekend.