Strange fermentation behaviour (WLP002)

Hi everyone.

2 days ago I brewed an AG imperial stout (OG: 1.100), plan on aging it ready for christmas!
After vigorous aeration (done with a massive whisk) I pitched a 2L WLP002 yeast starter when it was at temperature - 66.3F, however, I've noticed a large lag time, and then strange behaviour after.
After 18 hours there was no change, I then went to stir it and saw a large krausen forming. There is now constant bubbling, a great smell, BUT, my BrewPi tells me that there is and has been no increasing temperature, which has happened in all previous brews, and which is expected. It's clearly now fermenting, but I'm pretty concerned (and incredibly impatient!)
I have some concerns about the starter I pitched, I know the yeast was approaching its best before date and may have been pitched colder than the wort. Maybe underpitching caused the delay.
Am I massively overthinking the whole thing, or should I pitch another vial of WLP002?
Cheers

 

I know this might be off topic for you. I am assuming you did a 5.5 (or there abouts) gallon batch. Based on that, I think you under pitched.

I used: https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/. Based on that calculator, using a stir plate and the fact your yeast was old, you would need to do a 2L starter followed by another 1.75L starter (possibly more based on your yeast age - I did 4 months old).

This would be the reason for your slow start. The yeast were building up and, in the process, probably a bit stressed.

Good luck.

 

Don't sweat it - now that it's fermenting, it will do fine - keep her closed up, keep the temp steady and you're good to go.

Go have a beer!

 

If it's fermenting, you're probably fine. RDWHAHB.

 

18 hours is not really a long lag time.

How old is old? With the calculator that I use, I have to use a production date of 3-29 for 2 liters to be too little. It would have to be quite a bit older than that to get to levels that would concern me. 2 liters might have been very slightly on the small side which would increase the lag time. Not enough in this case to cause concern.

The only concern would be with the high gravity causing the yeast to stall when the alcohol level increases. If this happens you might have to pitch more yeast.

How are you controlling your fermentation temperatures? If you have a chamber and temperature controller, it should keep the wort temperature stable even during the fermentation.

 

Oh, I missed that. Yeah, 18 hours is no time. I don't start worrying til I hit 72.

 

Old is old - I can't recall it's manufacturing date, but it's best by was around mid-may.
Should I pre-emptively pitch more do you think? or wait and see if the yeast can cope, and work through it?
Yes, fermenter is in a fermentation chamber, and temperature is being taken via a thermowell. I've had a look at the BrewPi page and I'm starting to think it may just be incredibly effective at keeping it at the desired temperature range. On the other hand in previous brews temperature has fluctuated much more so than in this one, although still by only 1°C or so.

 

Are there any real negative effects of this on the beer? Or is it more a sluggish start?

 

There aren't necessarily any negatives to a slow start (though I maintain that 18 hours isn't slow). HOWEVER, if the reason for the sluggish start is that you did indeed under-pitch, there can be some other side effects related to the under-pitch if it stresses the yeast, like poor attenuation, off-flavors, or unwanted fruity esters. It'll still be beer, and probably a good one. Just not necessarily exactly what you were hoping for.

 

Would pitching another starter help the situation?
I'm sooort of aiming for fruitiness in the imperial stout, although nothing excessive.

 

Stressed yeast make more aromas. Do you want/like that?

 

Depends on the aroma

 

I have to say I'm leaning towards getting a new vial of yeast (soonest it could come is Thurs), making another starter and pitching it at high krausen. I'd be fairly surprised if in its current state it's able to get to the FG. Definitely going to do some wider reading about yeast and the process though, its so interesting. What do you reckon?

 

If it was only 18 hours before noticeable fermentation happened, I really don't think you'll have much to worry about. I've had beers go 96 hours before, and they ended up okay.

 

I looked at the calculator I usually use and if you made the starter on a stirplate, you may have underpitched very slightly, IMO. 18 hours, again, is not a terribly slow start. I get some at 3-4 hours most by morning - so about 12 hours or so, and almost all by 24 hours but many are not going when I leave the house the next morning.

I don't see anything of concern. I would only re-pitch if you wait a couple weeks, take a gravity reading and it is too high. Until you have that proof that the yeast did not finish, it is not necessary to add more yeast. Again, my opinion.

http://www.yeastcalculator.com/ I use the K. Troester method of aeration in the drop down menus.

 

I don't have a stir plate unfortunately - the starter wort was aerated, yeast pitched, and then shaken every now and then. I then cold crashed it for a day, decanted, let it warm and pitched. I suppose the active fermentation is a good sign though!

 

Without the stirplate your yeast starter will not have produced as many cells as it would have with one, most likely. But I still believe that, though an underpitch it is not serious enough to be terribly concerned, unless you don't get as much attenuation as needed. Then you can pitch some more yeast. You might need a more alcohol tolerant strain.

 

The recipe, and brewing software, suggests an FG of 1.028. Should hopefully equal out at a 9.5% or so beer. I'll keep taking readings over the next 3.5 weeks though.
i've had the temperature at 66F, although am tempted to move it down to 65F for the next few weeks - although considering the potential stressed yeast situation is this a bad idea?

 

I think you're overthinking it. 65 vs 66 will have a negligible impact on the yeast or its behavior. Relax and let it ride.

 

Ah you're right. It's so hard not to obsess and over think.
Will report back with the gravity in 2 weeks.

 

I agree the one degree difference will make no detectable difference.

I would leave it at that temperature for 7-10 days then ramp up over a few days to the low 70s.

Leave it alone. Don't take any gravity readings until the krausen has fallen and the beer has cleared. The first I ever do is at day 14.

When you do take a gravity reading do it with the plan of having final gravity. 2 reading that are the same which indicates it is safe to bottle.

 

Planning on bulk ageing for 3 - 6 months, then bottling - likely with champagne yeast. Was also going to keep it in the primary for 30 days in accordance with the recipe

 

30 days in primary seems excessive but it will not hurt anything. Through procrastination on packaging I have left quite a few on primary that long.

 

I thought the same, however it's what the recipe suggests: http://www.homebrewtalk.com/showthread.php?t=238807

Regardless, I'm in no real rush - the aim is to have it in bottles for christmas, so plenty of time.

 

I usually don't check the gravity til day 21 at least.

 

When I started people were starting to go from primary and secondary to primary only. There were more posts stating that you need to primary for at least a month and a lot that said 2 weeks. I started doing 3 weeks to split the difference. Later my pipeline was low so I did a few at 2 weeks and saw no difference.

Now I go 2 weeks.... But often don't get around to bottling or kegging for another week or a lot more.....

 

I usually go a month in primary, and if I'm lagering or adding fruit, six to eight weeks in secondary. It's longer than I need, but I brew a lot of big beers and dark beers, so they're just going to be bottle conditioning anyway.

 

I regularly go to keg or cask in ten days or less with WLP002. If you control the temps (e.g. pitch active starter at 64-66F and ramp from day two to 72F on day five) and it's not too extreme a beer, it'll probably be done and dropped clear on day seven. With cask, I then transfer at 72F and prime for cask conditioning at cellar temps (55F), and it's ready to drink in another week.

 

For anyone still interested I thought I'd update on the Gravity situation!

Checked it for the first time yesterday and it had gotten down to 1.030 with one week left, sitting at around 9.5%.
I'll leave it for another few days and take a reading, then another few days after. Seems to have fermented pretty nicely though despite my fermentation fears, the sample I tasted was beautiful!