There is a difference between ergosterol and UFA levels between high krausen and quiescent cells.
Yes, but by how much
? Is this measurable? After two days on a stir plate, will my yeast have 98% as much nutrients in reserve as they did at high krausen? 75%? 50%? How big of a difference is significant for fermentation performance, given the fact that these same nutrients are going to be available in 20x more quantity in the wort the yeast will be pitched into?
Kai Troester also did some experiments where he showed that high stir plate speed significantly increased the number of cells grown in the same starter culture when compared to a low speed with no vortex (http://braukaiser.com/blog/blog/2013/03/25/stir-speed-and-yeast-growth/
). Presumably, a non-stirred starter would grow the same number or fewer cells than the low speed starter. If I grew X number of cells using a James Bond starter, and 2*X cells using a stir plate starter, but the stir plate starter cells had 50% as many nutrients in reserve as the James Bond cells, what difference in fermentation performance can I expect, given that after a single replication period, the James Bond cells would be at 50% reserves and number at 2*X?
I'm also wondering whether shear stress can cause permanent damage to a culture. Let's say I grew a culture on a stir plate, cold crashed it, then decanted the spent wort. Then I added fresh wort, removed the stir plate, and let the starter ferment and the cells rebuild their reserves. Are the cells going to be different (e.g. mutated? damaged?) compared to those in a non-stirred starter inoculated with a smack pack? Does this potential damage heal when the culture is allowed to grow in a non-stirred medium (e.g. when fermenting a 5 gallon batch of beer)?