I'm a newbie here and planning on cold crashing my second batch before bottling, an extract-brewed IPA. I have a lot of trub in my fermenter (I'm still figuring out how to separate the break before pouring the wort and ended up leaving very little behind in the brew kettle). I pitched with a 1L starter of Wyeast West Coast IPA at 24 hours, but didn't get a total count. Fermenting seems to be going well 4 days in. My question: is there ever a time to be concerned about inadequate carbing after cold crashing, and is there a downside to repitching yeast at bottling? Is this ever a good idea? Many thanks.
Read up on this for my first batch and everything I saw said it shouldn't be a problem, there will still be plenty of viable yeast in suspension after a cold crash. People have cold crashed for weeks and still had no problems bottling and getting good carbonation without adding any additional yeast.
The only time you really need to worry about there being enough yeast in suspension to carb up a beer in the bottle is when you are long-term aging a beer, such as a sour or really big beers that benefit from extended aging in a secondary. Reducing trub going into the fermenter is an ongoing battle for a lot of home brewers and I suspect you'll find some threads on this if you search for them here. In the mean time, just let this ferment until its done, add your dry hops (if any), and bottle it up.
I don't think there's anything wrong with leaving a little beer behind in the brew kettle. There's nothing wrong with adding a little bit of the cold break into the fermenter either. I wouldn't want all of it in there. I just stop pouring when it starts to get thick. Causes for concern in bottling: Extended periods of time, poor yeast health, yeast at their ABV tollerance, inadequite yeast count, cold crashing for too long. You can always add yeast to the bottling bucket. Just make sure the attenuation isn't higher than the yeast you've already used and you'll be in good shape. I usually add half a pack at bottling when bottling beers > 8%. These beers have a tendency to sit in primary for a month and then go to the bottling bucket. The strains I use are med to high flocculating and I don't cold crash. After racking, adding priming sugar, and yeast, I give the bottling bucket a gentle stir with the brew spoon. No sloshing and no worries. If I were doing a West IPA, I'd check the gravity at 10 days, and at 13 days. If they were the same number , I'd dry hop for 4-10 days and you can cold crash for 3 after that if you want. Rack to bottling bucket and don't add any yeast. Enjoy 2 weeks later.
I routinely cold-crash/age for 3 weeks at ~39 . . . never had a problem with bottle carbing. Agree with @GeoSteve , the time to re-yeast is after really extended aging (months). The only downside of re-yeasting is sanitation/oxidation (and I guess expense and aggravation). You only need a smidgen of yeast for normal bottle conditioning, around 1 million cells/ml which is not much . . . invisible to the eye. If a beer needs extra yeast then CBC-1 is a good product. RE: Trub ... you mention pouring your wort. First, try whirlpooling (stirring with a spoon), then wait at least 5 minutes. You may have more control over leaving trub behind if you auto-siphon to fermenter.
When I bottle conditioned lagers, I worried about this. So I added a quarter pack or so of rehydrated yeast to the bottling bucket, stirred gently to distribute, and then bottled. However, I tried a batch without doing this and it carbed up well, and I stopped the practice. It was reassuring, but not necessary.
