It would great to have another yeast show.

I read the Yeast book and really enjoyed it, however I have a few questions.

What is the fastest that you can crash your beer without causing the yeast to be stressed and excrete fermentation by-products? I have read 2-4 degrees per day for German brewing, but was wondering what the max was if your beer was finished after a D-rest.

It was interesting to read that if there are say 200 billion cells going into a 4L starter or 100 billion cells going into a 4L starter, the starter with 100billion cells will grow more yeast. Is there some type of formula to calculate the cells in a multiple starters?

On top of that qns on crash chilling, what would be the appropriate temperature to crash chill an ale or a lager. I have done rapid crash chilling to 3c before when I first started, as the term to crash chill seems that it is done fast. However I found out that it added an enormous amount of green apples to my beer which tasted great after it complete the primary fermentation in the fv. However, my practice of chilling it too fast added those off flavours which took longer to condition out again. By then, the beer may not have enough yeast to clean it up since it may have dropped off during the chilling.

I recently read that a craft brewery crash chill their ales to 16c/62f, and all the while i've been over chilling it! Darn it

I drop my ales to 39-40F and haven manged to bottle condition even after that.