Cold crashing starters

I make starter for essentially every beer I use liquid yeast in. I have noticed that when I am making a smaller starter (around 1L) the night before brew day and pitch the whole thing right off of the stir plate that I end up with activity usually within a couple of hours. Now when I cold crash them I don't expect them to be as active when pitched, but I am also wondering if the yeast are going into more of a hibernation and becoming permanently less active.

For example, I made a 2L starter of Wyeast American Lager and fermented it at 60F. After 2 or 3 days when it was completely finished fermenting I put it into a 40F fridge and let the yeast drop out of suspension. Then on Brew day I decanted the beer off and pitched the slurry into 48F wort and have kept it there since. Is this an alright practice or is the 20F drop from the stir-plate to the fridge enough to cause them to put up a protein coat and not be as active when added to the wort? It is fermenting so I know they are alright, but I am just looking for the best method to keep the yeast viable when decanting is in order. Should I be dropping the yeast temp at a slower speed such as the standard 3-5F a day or is it okay for starters to be cold crashed?

Do you (or anyone else) think an 8 degree differential between the yeast temp at 40 versus the wort temp at 48 is enough to cause a significant lag?

PseudoChef said:

Do you (or anyone else) think an 8 degree differential between the yeast temp at 40 versus the wort temp at 48 is enough to cause a significant lag?

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In practice, I'd say no... but that's just my experience. It might cause a slight shock and possibly off flavors, but if you're not having problems..

I don't know about the protein coat thing, but I can say that lager yeasts need a couple days of cold-crashing to come out of suspension. Not sure how long you crashed them, but if you crashed them ~24 hrs before pitching, there will still be a ton of yeast in suspension and if you decant the starter beer, you're losing all that yeast and it will result in a longer lag time than you expected.

I don't see a problem with cold crashing starters... especially with lager yeast.

I see a problem with cold crashing ale yeast. When you pitch yeast, you want the temperature of the slurry to be as close as possible to the wort. In the case the OP mentioned, we were talking like 4F. But 30F is going to be a big deal.

Any cold-crashed starters would surely be warmed up close to the same temperature as the wort before pitching, n'est ce pas?

With ale yeast I will often pitch the starter when active, but if I do cold crash it I will decant and let the slurry sit at room temp while I brew to warm it up. As for lager I will cold crash and pitch at about 40F into a 46F wort, I never thought this to be too drastic of a temp increase. I actually figured they would like warming up a few degrees like that to wake them up.

As for cold crashing lagers I always give them at least 3 days to fully floc out. I guess my concerns with yeast going semi-permanently dormant after cold crashing are unfounded and I glad to hear so.

z987k said:

I see a problem with cold crashing ale yeast. When you pitch yeast, you want the temperature of the slurry to be as close as possible to the wort. In the case the OP mentioned, we were talking like 4F. But 30F is going to be a big deal.

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Ah, but what about just good old fashioned common sense? White Labs and Wyeast recommend their smack packs be brought to room temperature before pitching; why should we assume any different with cold-crashed, decanted starters?

flyangler18 said:

Ah, but what about just good old fashioned common sense? White Labs and Wyeast recommend their smack packs be brought to room temperature before pitching; why should we assume any different with cold-crashed, decanted starters?

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Exactly.

I don't cold-crash either one...I just let them go until they're done (ale starters @ ~70 F and lager starters at ~60 F) and decant the liquid and pitch the slurry (I pitch ales @ 68-70 F and lagers @ 58-60 F). The decanted liquid is clear so I assume I'm not throwing out too much yeast.

It's prob not accomplishing anything but I actually use my primary lager fridge as an intermediate for the smack packs/vials. They never go from the 40 F fridge to room temp...always to the 50 F first.

Seems within a reasonable range yeast are fairly forgiving and the beer will usually still turn out as decent beer. I used to make teeny-weeny 2 cup starters from the Wyeast Propagator packs (the small 25 billion cell count packs) and many beers still finished dry (but prob not as good as they could have been).