Yeast Started - "when is it too old"?

Should b fine.

I've kept slurry for 2 months in the fridge with no problems.

 

Are you saying it's still whirring around at a temp in the 70s? IMO, six days is pushing it. It will probably work but you aren't pitching the little buggers at the top of their game. A couple of suggestions: 1) Add some wort and let it take off again, then chill/decant/pitch . . . or . . . 2)Chill/decant now (~24 hours), then start another round with Mr Stir-plate. It's not uncommon to take almost a week when making a multi-step starter, that's essentially what this is accomplishing. If the calculator says you will have too much (which is possible), just pour off the excess and chill/store for the next brew day.

 

Put it in the fridge, definitely not on a stir plate.

On brewday decant and either add some new starter wort and shake the shit out of it (or use a stir plate or aeration stone) or just pull some wort at some point during the brewing process, cool it, add it to the yeast and aerate.

Anyone care to take a stab at how long you even need the stir plate? 24 hours max?

 

According to White Labs you should turn off the stir plate around the 18 hour mark:

“You probably won’t see any visible activity, but the yeast is busy taking up the oxygen and sugars in the solution and growing new cells. After 18 hours, the yeast will have consumed all of the nutrients and oxygen in the starter. Switch off the stir plate or discontinue shaking and it will form a milky white layer on the bottom of the container as the yeast flocculates. If you are not planning on pitching the yeast right away, you can store it in the refrigerator with the foil still in place.”

https://www.whitelabs.com/resources/homebrew-starter-tips

Cheers!

 

Sweet thanks, hadn’t read that.

 

You don't even need to add new wort or agitate it. Just decant and add it to your fermenter. Or don't decant and add it. Which ever floats your boat.

That's sort of the answer. If you're pitching a standard, fresh package of yeast from a lab into a standard amount of starter wort, that's probably pretty accurate. The actual answer is that it depends upon your inoculation rate and the volume of your starter wort. Since S. cerevisiae strains multiply better in an aerobic environment but ferment better in an anaerobic one (Pasteur Effect), a stir plate is only needed while the starter is in its log phase, so once you see visible signs of fermentation, you can take it off of the stir plate and either put an airlock on it and/or cold crash it.

 

Not sure I follow your logic here. What is advantage of adding starter wort and shaking just prior to pitching. In all cases the yeast has to complete the adaptive (lag) phase again.

In Yeast they expand on this: (paraphrasing), Most starters reach maximum cell density within 12 to 18 hours, some extend as long as 36 hours, the bulk of growth should be complete within 24 hours.

Not mentioned, but I find true, is these figures apply to after the yeast become active. Due to strain, age, temp, ph, you might have 1-2 hours before the starter takes off or it may be 10-12 hours . . . just depends. Last week I re-started an old 3944 which took off in <2 hours and 24 hours later was still doing a Mt Vesuvius imitation . . . I could have stopped it at the 18 mark but I let it rip till the smoke cleared.


I let the yeast tell me when they are finished. Sometimes there is a beautiful krausen, sometimes it's puny, and sometimes it's non existent. If you cut off the stir plate for 30-45 minutes then give it a hard shake and off-gassing occurs then the little guys are still growing. This is CO2 created by cellular respiration, i.e. the party is still going on. At some point it all settles down and no more off-gassing results. I typically give it a couple more hours before calling it done.

Also not addressed, but I find true, is when doing multi-steps it is acceptable to boost the OG (1.040+) during the later steps because the yeast has already proven it's ready/able/willing. This would apply to the OP if he decides to add a starter step.

 

What is visible evidence of yeast fermentation, as opposed to aerobic respiration, which is what is going on in the log phase? Both create CO2 bubbles, but other than bubbles, what are our visual cues that give insight to the biochemistry?

 

I see what you are doing here with all all of your post now

 

The only thing that you can really do in these cases is watch for the very beginning of krausen formation.

 

Differences in viability and cell count are certainly the main reasons for variability in log phase times, as long as the volume of the starter is held constant.

Here's the thing, you CAN keep oxygenating your starter while S. cerevisiae are fermenting and you really won't have any issues. That said, people should know that it's not helping your starter once active fermentation begins because oxygen inhibits fermentation somewhat in this species of yeast. Again, see Pasteur Effect for the reason why this happens:

https://en.wikipedia.org/wiki/Pasteur_effect

I'd say "acceptable" is the right word, because it's certainly not necessary unless the specific gravity of your starter and the specific gravity of your main wort differ greatly and you're worried about osmolarity issues, which aren't going to be the end of the world anyway.

 

I’ve gotten into the habit of creating 5 different starters for each packet/vial of yeast at the time that I open the packet. That means the the oldest starter will sit for two or three months in the fridge. I don’t see how this is any different from yeast sitting in a vial in a LHBS for months. Haven’t had a problem. Cold yeast is just inactive yeast.

 

That's a good habit to have.

You're right. It really isn't much different, though starters have beer as the medium while liquid yeast is probably packaged with something along the lines of a Ringer's solution.

Well . . . less active, at least.

 

But either way, it is actively dying.

True. And it's dying more slowly.

 

So, @magoo0903 , what did you end up doing? It's okay to say you followed someone's advice or you blew us all off and tried something different.