Cheese Making Fundamentals Leeners, Northfield, Ohio has this excellent page that explains it all!

Making Cheese at Home by Dr. A.R. Hill, Department of Food Science, University of Guelph, Ontario, Canada

Fankhauser's Cheese Page by David B. Fankhauser, Ph.D., 
Professor of Biology and Chemistry, University of Cincinnati Clermont College, Batavia OH, I think is one of the best out there on the subject!

rev. 3/08