significant ph drop during fermentation

[woohokie]

Having what I perceive as an odd issue lately. The beer:

Dark mild at 12P
KO ph cooled in to 67f at 5.1 (slightly low but meh)
24 hours in 9P and 4.4ph (seems like a huge drop)
48 hours in 4.3P and 3.95ph - way low, tastes tart

Yeast is wyeast 1318 gen 3. Cell count showed .8bil cells/ml with 96% viability so 35.2lbs of slurry was pitched into ~ 8bbls of wort. I've had this issue happen with other beers and although the ph seems low at this point (not quite ever 3.95) the beer always finishes up and seems to correct itself to 4.25-4.35 range generally.

My first thought is that my cell counts are drastically off (given how many pounds of slurry I'm pitching it sure as hell seems like way too much) and that I'm overpitching - would that cause this ph issue? In my defense, I've counted other strains like Conan or Chico and have gotten the normal densities you'd expect to see (1.5-2bil cells/ml) and this 1318 strain from 2 different suppliers always seems to have the same low cell count upon harvesting.

I've learned not to freak out until it's time to in this business, but I'd like to understand what might be happening and how to resolve this issue. I've also had this happen with wlp007 and a Conan variant.

Any ideas?

[brewmaster 2011]

Seams to me it might be some sort of infection. Have you plated to wort going into the fermenter after the HX.

[woohokie]

Seams to me it might be some sort of infection. Have you plated to wort going into the fermenter after the HX.

I haven't yet, and am completely unsure how to go about it. Are there any user friendly type kits for this sort of thing?

Would this be adequate/all encompassing?

http://www.whitelabs.com/other-products/tk3100-white-labs-hlp-test-kit

[soia1138]

These numbers don't seem odd to me. It's a strong ferment, possibly from an overpitch but it sounds like a healthy ferment to me. Seeing as this isn't finished yet I wouldn't worry too much about infection, the tart is from all the yeast present in the sample. If it was terminal and it continued to drop then I would assume infection. Let it ride, could be the best batch yet!

[Junkyard]

Like you experienced, with our English strain it will drop pretty low on the 4th day with a slight overpitch. Usually no more than about 4.1 or so, and then always corrects itself on day 7-8 to about 4.3. If your ph stays low I would point towards infection, but if it corrects itself back up a few notches I would consider that very normal.
1318 is a strong flocculator right? I wouldn't think you would need 35 lbs of slurry, seems like double what you'd normally need for 8 bbl. Is your fermentation showing any other signs of an overpitch?

[woohokie]

Like you experienced, with our English strain it will drop pretty low on the 4th day with a slight overpitch. Usually no more than about 4.1 or so, and then always corrects itself on day 7-8 to about 4.3. If your ph stays low I would point towards infection, but if it corrects itself back up a few notches I would consider that very normal.
1318 is a strong flocculator right? I wouldn't think you would need 35 lbs of slurry, seems like double what you'd normally need for 8 bbl. Is your fermentation showing any other signs of an overpitch?

Checked the beer today (72hrs in) and we're at 3P and 4.08ph, so we've gone up a little bit which I'm happy with. I haven't tasted it as I had one of my crew check it out while they were on site.

I also wonder if I'm over pitching as I mentioned but the cell counts always look incredibly thin for this strain. When I count Conan or Chico they look normal - usually ~ 1.4-1.8 bil cells/mil which for 7.5bbls usually means a 10-12lb pitch depending on the gravity... Trust me, a major wtf moment happens when I see my spreadsheet ask call for 35lbs of yeast when it's 1318 vs 12lbs for say Conan.

[woohokie]

If that is a room temperature measurement, 5.1 is not just meh. It is several tenths low and that echos into the beer. But the beer ending up under 4 is not typical. The advice to plate the beer to search for contamination appears prudent.

I wasn't thrilled with 5.1 knock out ph, with my usual target being 5.2, I wasn't aggravated enough at it to take further action. Which brings me to another question - if I find a KO ph low or high by a tenth or two and decide to adjust it, is taking the time to do so while say the wort is still hot in the whirpool worthwhile? Wouldn't that add quite a bit of time (from a quality standpoint) to other processes? I guess what I mean to ask is, does a parameter like KO ph take precedent over others? I realize it's best to nail ph at all points without adjustment but that doesn't always seem to happen.

[Junkyard]

Checked the beer today (72hrs in) and we're at 3P and 4.08ph, so we've gone up a little bit which I'm happy with. I haven't tasted it as I had one of my crew check it out while they were on site.

I also wonder if I'm over pitching as I mentioned but the cell counts always look incredibly thin for this strain. When I count Conan or Chico they look normal - usually ~ 1.4-1.8 bil cells/mil which for 7.5bbls usually means a 10-12lb pitch depending on the gravity... Trust me, a major wtf moment happens when I see my spreadsheet ask call for 35lbs of yeast when it's 1318 vs 12lbs for say Conan.

Conan is a low flocculator right? and chico is a medium flocculator. It makes no sense that they would flocculate out thicker than an English strain. Especially for a beer like a mild with little hops and most likely little trub going into the fermenter.

I see 5.1-ish KO ph with stouts sometimes and when that happens I usually blame myself for not adding enough baking soda, usually the beers turn out great, but maybe not quite as creamy as they could have been...

[dick murton]

I can't comment on this particular strain, but we used to regularly get 3.7 at end of ferm when brewing ales - dropping from 12 P to about 2.5 P over 60 hours, with, as you have experienced, a slight lift after the main fermentation, which we always attributed to slight yeast autolysis. Fermentation temperatures were generally higher though - say 22 C (72 F). It might be worth checking your thermometers for accuracy - this might turn out to be a simpler answer than infection or overpitching.

The key to all this is what the beer tastes like. If it is a new brew, and you, and more to the point, your customers like it, then leave as is. If they think it is too acidic, then try lowering the pitching rate - but not too drastically at each step.

Has anything else changed? Water source, water treatment method or rates?

[woohokie]

Just a quick update, the beer in question rose to 4.13ph and was subsequently crashed at 140hrs after hitting 2.6P finishing gravity (showed for two days consecutively). It's in the serving tank and seems to be fine after all. It's all primarily going to be served in house so I'll keep an eye on it should it begin to go tart/sour.

Thanks again for all the help. I've sourced some sterile cups to begin to forced wort tests post HX and post FV fill.