Getting a sour mozzarella.

[paulriccio]

I am using raw milk and a thermophilic culture.  My cheese is getting sour before it gets to 5.3 PH.  Could using too much thermophilic culture make it sour?  From what I read, and emailing a local cheese maker, it seems I should be able to get it to acidify in 3 to 4 hours.  My only successful, non sour cheese had less than a dash of culture.  It took almost 48 hours to acidify.  The curd ended up being pretty dense too because much of the whey left.  Could I be leaving it in the rennet too long?  I am soooooooooooo close!!!!  I want to change one thing at a time so I know the causes of things.  I had it in the rennet for an hour and a half. 

[Kern]

Welcome to the Forum.  You haven't supplied a whole lot of information.  What was the batch size?  Specifically, what culture was used?  What was the culturing temperature and how long was it cultured?  How much time did it take after adding the rennet to get a "clean break"?  Were the curds cut after the "clean break"?  What size cubes?  How long after cutting and at what temperature were the curds "cooked" before separating from the whey?  How are you measuring the pH?

Answer these questions and someone will be able to supply an opinion.