pH and Ferementation

[Trub-Man]

We have been monitoring our pH during fermentation a little more closely. It drops nicely to a pH of 4.03 once attenuated but the starts to creep up to 4.19 to 4.23 over the next 4 days. Wort to the fermenter is around 5.3.
Question what do you think is going on, why is it creeping back up?

And yes we do crop the yeast off the beer, so autolysis is not the answer.

[Iso-Alpha]

Co2 will bring it back up. Try de-gassing your sample.

[zachjenny]

pH

Yeah, i've seen that before in a brewery that I used to work in. The pH would level off after it attenuated, then gradually rise over the next couple of days. We figured that the beer would be higher in CO2 (carbonic acid) initially, and after a few days, the CO2 would gradually dissapate out of the racking arm, hence raising the pH. Just a thought.

[dick murton]

If the yeast autolyses when it settles as a thick sludge, the pH rises. If your yeast is dying off early due to lack of zinc or oxygen, it will also die off early and start to autolyse. Don't allow your beer to stay over the yeast once it has finished fermenting and the bulk of the settling has taken place, even if you crash cool it all. Some yeasts take a few hours to setle out, some take days - so difficult to be specific on time. Even after you crop the yeast there will be plenty for a diacetyl rest.

Cheers

[damoller]

Pitching rate

Over pitching can also cause very early autolysis even befoe fermentation is finished!

[Greenbrewmonkey]

Good, or bad for my entire brewery life, no matter where the brewery, I have seen a small rise in pH after the end of primary fermentation. Usually not as much a jump as you have observed. Is this a new thing, or just a new observation? In most cases in your FV, even with cropping, there will be more than enough yeast to cause a slight rise in pH. I agree with Dick, move it off as soon as possible.

I think a more important question is, how's the beer? Is it fantastic, or does it have a nasty, autolysed yeast bite. If the answer is fantastic, don't worry about the rise (unless you are shooting for a high level of stability and are worried the relatively high pH indicates an increase in available nitrogen: microbe fuel!)

Just maybe?

Cheers,
Ron

[Ken Jennings]

pH and Fermenters

Many people claim they can tell all sorts of things from taking the pH of fermenting beer....(Lactic acid bacteria will make the pH go down, autolysis will make the pH change...ect...ect.) The fact of the matter is that none of these things make a difference and their claims are much like reading a Ouija board!
The fact of the matter is that as beer ferments it produces CO2 which is acidic (and carbonic acid) and lowers the pH. How much CO2 remaining in solution determines in a large part the pH of your beer in the fermenter. When you collect your sample it is a little like hitting a moving target as CO2 comes out of solution and the pH climbs again (especially if you use a stir bar in your beaker w/pH probe). My suggestion....forget it....pH of beer in fermenter tells you nothing...hitting a moving target as CO2 comes out of beer increasing pH. If you want to know about autolysis use your taste buds or a microscope. If you want to know about Lactobacillus or Pedios use agar. In my humble opinion autolysis is rare.

[dick murton]

Maybe autloysis doesn't happen very often in your brewery, but I know from tasting beers that it certainly does in other breweries. Ok this was in filtrate recovered from yeast cones from 1000 and 2000 hl vessels, but I have seen pHs go up to about 5.2, when the bulk of the beer was at less than 4.00 We certainly knew how to mishandle the yeast occasionally !!

Cheers

[steveg]

Totally normal.

We have been monitoring our pH during fermentation a little more closely. It drops nicely to a pH of 4.03 once attenuated but the starts to creep up to 4.19 to 4.23 over the next 4 days. Wort to the fermenter is around 5.3.
Question what do you think is going on, why is it creeping back up?

And yes we do crop the yeast off the beer, so autolysis is not the answer.

This is a totally normal part of fermentation. You have nothing to worry about. Yes, it is caused by slight autolysis, but also dormant yeast yielding up some organic material that adds buffering capacity to the beer.

Keep in mind the beer can still look pretty bright with 8 million yeast cells/mL in the beer! That is still a lot of yeast that will be going dormant and autolysing at a rate of 3-15% of the total at the end of fermentation.

If you are capable of doing cell counts, check it out and you will see!

I see it every time I have ever profiled a fermentation at any of the breweries where I have worked. You have nothing to worry about.

[Ken Jennings]

Fermenter pH and autolysis

Wow,
1000-2000hL fermerters! That's a lot of head pressure = Heat. Yes, with that large a vessel autolysis in the cone could definitely be a problem. But I think he said he emptied 'em. Yeast are not pieophilic organisms (word for the day).
I guess in that senerio the lesson to be learned is: If your going out and buying that big (1000hL) a fermenter, pony up the extra cash and buy cone cooling which would go a long way in solving that particular problem...but I thought the Brits like that Vegemite...er' or is it marmite flavor!

But with all seriousness aside, I guess I wrongly assumed we are dealing with much smaller vessels in this thread. I still believe that the pH in you sample has much more to do with the CO2 content of that sample....and assuming (theres that word again) that you are using a bench top pH meter, the CO2 content will change on the way from the fermenter to the pH meter. Making the results hard to interprete at best, verging on next to worthless especially if you are using a stir bar in your beaker.
Bottoms Up,
Ken

[dick murton]

Just out of interest - 2000 hl vessels, including cone cooling. Temperature of beer just above the cone - 2 deg C. Temperature of yeast right next to the cone jacket, where there happened to be a temperature probe because we used it for cultures. Temperature in the centre of the yeast - 49 deg C - after just a few hours (not sure exactly how long, but somewhere in the region of 48 hours after cooling the beer to 2 deg C I think) The cooling jackets could cool beer at greater than 1 deg C / hour.

Yeast is a pretty good insulator !!

Cheers

[steveg]

Just to clarify.....

This is a totally normal part of fermentation. You have nothing to worry about. Yes, it is caused by slight autolysis, but also dormant yeast yielding up some organic material that adds buffering capacity to the beer.

Keep in mind the beer can still look pretty bright with 8 million yeast cells/mL in the beer! That is still a lot of yeast that will be going dormant and autolysing at a rate of 3-15% of the total at the end of fermentation.

I realize now I may not have been clear in this previous posting. When I refer to this yeast autolysis and dormancy issue giving a pH rise, I mean even after the yeast has been removed from the cone. I kid you not when I say that just the yeast in suspension will give you enough buffering material as it dies or goes dormant to raise the pH.

Also, I am referring to the pH of de-gassed beer. To properly measure the pH of a fermentation sample put the beer in a juice jug, like a Welches cranapple jug (thouroughly washed of course) and seal it. Allow the sample to attemperate to room temp. Shake for 20 seconds or so, unseal the cap to evolve gas, reseal it, shake it again for 20 seconds or so, unseal the cap to evolve gas, and repeat until no more gas comes out of solution. Now you can pour into a cup or beaker and measure pH. You are now taking a proper pH of beer according to the ASBC and EBC! You should still see the rise in pH at the end of fermentation using this method!

I encourage everyone to measure their pH over the course of fermentation. You'll know what a normal rise is and what is a potential problem (like yeast autolysis at levels that will affect flavor, or worse yet caustic contamintation).

Also be honest with yourself: some yeast autolysis at very low levels will occur. That is the nature of dealing with thousands of liters of beer with peak cell counts at 80 million cells per milliliter! You're going to get a few cells autolysing and giving a slight pH rise! It will only affect the flavor when the autolysis gets really bad when you leave the cone full of yeast for days on end when the fermentation is complete.