do you let the pack swell up before you make a starter with it? in the past I generally didn't bother.
Yes, not allowing a smack pack to swell is throwing away its strength. When used properly, pitching yeast from a smack pack is like pitching a first-level starter at high krausen.
Are you saying that there's significant cell replication as it swells? Either I'm misunderstanding or you're at odds with what Wyeast says.
From Greg Doss in response to a question I emailed him in 2005....
Thanks for the email. I'm sorry to say that very little cell growth is
occurring in an activated package of yeast. Typically there is about a
10% increase in cell density. In any fermentation, yeast growth is
controlled by the depletion of a limiting nutrient. In the Wyeast smack
pack, sugar is the limiting factor. There is not enough sugar available
to provide the yeast enough energy to support a large amount of growth.
However, the nutrients that are introduced to the yeast are used for
cell membrane synthesis and nutrient uptake starting the culture's
metabolism. By starting the culture's metabolism before pitching, the
brewer can greatly reduce lag times. The CO2 which causes the swelling
is a by-product of this small amount of metabolism.
I hope that this helps. If you have further questions, please ask.