Is pediococcus a sanitation related issue, or something else? Denny has told me that it can cause diacetyl. I’m trying to eliminate possible causes as to diacetyl in a 1.051 APA, fermented with 1 packet of US-05 for 10 days at 66F. I did not take a final hydro reading, assuming 10 days was ample enough time.
It may have been enough time to reach FG but maybe not enough time for the yeast to actually finish its other work.
pedio is definitely a sanitation issue and can cause diacetyl. Also, oxidation can cause diacetyl to reform in the finished beer.
Ooohhh, good point, since I know the beer Jim is talking about was bottled from a keg.
Well, that diacetyl must have reformed in a period of 6 days then. Bottled on Monday, tasted on Sunday. Was there much head space in those bottles, Denny? I thought there was very little, plus I used Oxy Caps. Not arguing with you guys, just getting all the info out there.
Nope, virtually no head space. Several people wanted to know how you did that!
Did you purge the kegs with co2 when racking? was there a leak in your racking cane? Did you purge the bottles with co2? Any of those times could have introduced o2. Not idea if oxidation caused it, just sayin’.
I never thought about purging the kegs when racking…I do purge the headspace after racking. No leaks that I can see in my Super Siphon. I’m not sure how I would purge the bottles given my equipment, i.e., QD+hose+cobra tap. I insert a small length of vinyl tubing into the cobra tap nozzle for bottle filling. Not ideal, I know. Bottles were filled practically to the brim, and capped with Oxy Caps.
Wouldn’t oxidation have been detected by the taste testers in some other way other than by merely the presence of diacetyl? Thanks for the comments guys. I’m still learning.
10 days at 66F with US05 was probably enough time for the yeast to consume any residual diacetyl…did you taste the beer upon racking?
Also a small tip…after kicking a keg. I clean the keg with hot water then it gets a hot PBW soak overnight. The keg then gets another hot rinse and a quart of starsan solution shaken up inside.I then purge the keg completely with CO2…pulling the pressure relief valve multiple times to evacuate O2. I store the keg pressurized with CO2 until it’s ready to be filled. When ready to fill I just release the pressure and rack the beer into the CO2 filled keg.
This method mitigates potential oxidation.
I’m not sure that pedio infection is your problem here.
As others have pointed out, pedio IS related to sanitation, but it takes some time to develop. It’s more likely that you’re just getting normal diacetyl due to yeast action.
If you’re getting loads of butterscotch/diacetyl and also lactic (i.e., yogurty, without much aroma) sourness, you might have a pedio infection. If you’re just getting lots of diacetyl, but not much sourness, you probably don’t have a pediococcus infection, but you do have a fermentation issue.
I can tell you that the people who tasted Jim’s beer found low levels of diacetyl, and of the 8-9 tasters only 4 mentioned it (one of whom was me). There were no other obvious flaws in the beer and no other sign of infection.
Thanks for the update there, Denny. 8 or 9 tasters? Wow! I guess I won’t beat myself up over the 4 judges tasting low levels of diacetyl, although I will be using other liquid yeast strains for comparison.
purgeing kegs: If you add co2 to an empty (air filled) keg and then release the presure and then repeat you will not get all the o2 out. yes o2 is lighter than co2 but it is still a gas. alchahol is lighter than water but if you pour water into a glass of rubbing alchahol until it overflows an amount equal to the volume of alchahol you do not end up with pure water. fluids mix. They may not stay mixed but they do mix.
I like to fill the keg to the very brim, as close as I can get to 0 air space, with sanitizer and then force that out with co2. the result should be an almost perfect absence of o2 (almost perfect because 1. I can’t seem to get the keg totally full of liquid and 2. some o2 that is disolved in the sanitizer solution will probably come out as it drains and thus introduce some tiny amount.)
does this make a difference? I have no idea. this is how I have always done it but it seems like it could make a difference in the long term.
…however if you hook up the CO2 to the dip tube post and open the P.R. valve you will evacuate most if not all of the O2 in the keg.
that’s my point. doesn’t matter if you add the co2 to the bottom or the top, unless you go incredibly slow, there will still be alot of mixing, gases mix even better than liquids. I am sure it’s fine I am just saying that if the goal is to remove as much o2 as possible you have to start with a medium so much more dense than air that it will not mix.
Not to derail the original posting much further, but I’m not understanding all of this. After you’ve purged the keg, what happens when you remove the lid to introduce your siphon tubing? Does the CO2 not escape? O2 doesn’t enter the keg, displacing the CO2?
no, now the relative densities do indeed come into play. as long as you are careful not to move the keg much after opening, and you don’t tip the keg at all then the co2 sitting in the keg will not allow air to enter. co2 is heavier than air. you will see it if you dump the presure and open the lid the whole keg will be filled with vapour. that’s the co2 and it just sits there, although you can see it swirling around at the keg mouth a bit. then you attach your syphon hose to a QD and attach that to the beer out post and rack you beer gently to the bottom of the keg. This will force the co2 up and out as the beer fills and any minor amount of 02 that did mix at the keg mouth will leave quickish.
I agree absolutely that having a medium in the keg (or whatever) assures that you purge out all the o2. But I disagree that if you let the co2 run long enough that you don’t purge out most if not all of the co2. If you have a glass of milk and you pour water into it the water and milk will mix. But if you pour long enough you will end up with all water.
yeah, I admit it borders on ocd and probably doesn’t matter either way. just being a pedant.
Fluids DO mix. However, with gases you can take advantage of the pressure difference from your resident gas (air - oxygen) and your purging gas (CO2).
If you’re purging with CO2, you’re using 5-20 psig gas to purge 0 psig (atmospheric) gas. A few purges is with pressurized CO2 is PLENTY - as long as the purges come up to pressure and you’re not just blowing CO2 through an open valve.
When we have to push ALL the oxygen out of our batch reactors (at work), we use nitrogen at 30 psig. We use 3-30psig purges to get the O2 levels < 0.5%. Obviously, N2 and O2 are miscible - its the pressure difference that counts.