What did I do wrong???

[advancewithcourage]

I was making cheddar today and something happened I do not understand. I added my culture and let is ripen as usual. When I added my rennet on hour later, I only stirred it for a few seconds and it suddenly curded up like ricotta does when you add the lemon juice. The temp was right at what it was supposed to be and I used the same culture I have been using. Any ideas on what might have happened so I can avoid a similar mistake in the future?

Thanks!

[linuxboy]

You mean you added rennet and waited, and when you went to stir after cutting, the curds shattered? Or you added rennet and stirred to incorporate it in?

If the first, then you got bad milk. If the second, then something about the amount of culture or milk quality was odd because it coagulated due to acid. That acid-induced coagulation when the temp is around 95F happens at a pH of 5.2-5.3

[advancewithcourage]

It was the second. I thought it must have something to do with acid, but I am not experienced with any sort of hard cheeses. I have only made chevre and ricotta so far. I am wondering if it is my culture because it was about 2 weeks old? the milk was fresh from this morning, but I added about a half cup of milk from the fridge because I was shy of 2 gallons by that much. I wonder if the milk was not fresh enough?

[iratherfly]

Sounds abnormal if the milk was good and the culture was good and used as you regularly do. This may be related to a 3rd party acidifier such as...

Could there have been a residue of cleaner or sanitizer on your pot, vat, rennet/water cup, or whatever utensil you use to stir it in?

[kenjin]

Did you dilute the rennet with water before adding it?