How does beef, vegetable and milk turn bad by microbes? - Help required (Nov/24/2007 )

Is there any sites recommended to read more about how these food turn bad?

Read books like Food microbiology by Frazier or Adams. Fundamental and frontiers of food microbiology (book) will also help.

www.google.com

if you use terms like 'spoilage' you should get some good information. I would check websites like www.cdc.gov/ and the USDA's website; they should have some info as well that is pretty reliable.