Regarding yeast starters...

[denny]

I used to chill, decant, then let the starter come up to the wort temp before pitching. A couple months back though, Denny mentioned just pitching it cold, so I’ve been trying that method since. There has been no noticeable difference in lag time, attenuation, flavor, etc. due to yeast performance. It’s just my experience, and there’s nothing wrong with letting it warm up, or adding more wort, etc., but I find pitching cold to be far more… pragmatic…

Gold Star!

[mattt (SpanishCastleAle)]

I’ve been pitching cold for a while now and IME, if anything they take off quicker.

There was a question on cold-pitching in the Danstar FAQ and Dr. Clayton Cone said he wasn’t sure why it worked so well but he hypothesized that it may have to do with glycogen/trehalose reserves.  When you hydrate dry yeast in warm water (the best way to hydrate dry yeast) you need to pitch it relatively quickly because if you don’t the yeast start using their built-up glycogen/trehalose reserves.  He thought that perhaps letting yeast warm up prior to pitching had a similar effect; i.e. the yeast starts to use up it’s internal reserves until pitched into nutrient/O2/sugar rich wort.

[system]

@mabrungard

Just a length of typical 1/4 or 3/8" ID tubing, sanitized and inserted into the spent wort above the yeast cake.  Set the flask on the side of the sink and have the free end of the tubing extend into the sink.  A standard application of oral vacuum gets the flow started.  Since the spent wort is just going down the sink, the worries with contamination due to starting the siphon by mouth are non-existent as long as you keep the flow from back washing.

This is exactly what I do.  I also will toss the hydrometer sample in after to help stir up the yeast (making sure the hydrometer and cylinder is sanitized before collecting wort).

[slowbrew]

I decant or siphon off the extra wort from the starter.  Then run in some of the new wort I just boiled and chilled so I can swill it around to loosen up the yeast on the bottom.  After I finish transferring the wort to the primary I pitch the yeast.  Never had any issues.

Paul

[tschmidlin]

I’ve been pitching cold for a while now and IME, if anything they take off quicker.

There was a question on cold-pitching in the Danstar FAQ and Dr. Clayton Cone said he wasn’t sure why it worked so well but he hypothesized that it may have to do with glycogen/trehalose reserves.  When you hydrate dry yeast in warm water (the best way to hydrate dry yeast) you need to pitch it relatively quickly because if you don’t the yeast start using their built-up glycogen/trehalose reserves.  He thought that perhaps letting yeast warm up prior to pitching had a similar effect; i.e. the yeast starts to use up it’s internal reserves until pitched into nutrient/O2/sugar rich wort.

They will mostly “consume” their trehalose reserves within 5 minutes of coming to room temperature, but I don’t believe that has anything to do with it.  They make trehalose when it’s cold because it is a cryoprotectant and they are anticipating the temperature dropping further.  It also plays a role in dessication and ethanol tolerance.  Trehalose levels will drop because it is hydrolyzed to glucose, but we don’t know that that glucose is all consumed or if the excess is converted to glycogen for a while before the cell begins consuming it.  Consuming the glycogen reserves seems like a more proximal answer to me.  I’d love to get a grant to test this at length with a trehalose deficient mutant . . .