I took the liberty of generating a graph from the curve equations in
http://www.nyx.net/~dgreenw/whatisth...shipbetwe.html and I
believe also in http://aem.asm.org/cgi/content/full/64/7/2616 .

http://hans.fugal.net/images/sourdough_time_temp.png

or for printing

http://hans.fugal.net/images/sourdough_time_temp.pdf

Enjoy.