Expert: John Snyder - 5/13/2006

Question
hi John, i was just wondering why the pH of the yeast is so important during fermentation and why it drops towards the end of primary fermentation?
Also, what is the optimum temperature for fermentation?
Thanks.

Answer
Normal yeast Ph is 5.0 to 5.7.This is based on the make up of the yeast cells.Yeast Ph actually doesn't drop during fermentation.The fermentaion liquid does,from 5.3 on average to 4.3 on average.This Ph drop is due to production of Co2,organic acids,such as lactic acid,removal of buffers,formation of some inorganic acids,such as phosphoric acid.Ph usually falls 1 unit,or more.Yeast Ph is important as to it's biological state.

Lager optimum fermentation temperature is 50 to 55F,range 40 to 60F
Ale optimum fermentation temperature is 70 to 75F,range 60 to 80F

Hope this answers your questions,any additional info needed,please let me know

                 John