OK, I guess I was getting a little cocky today and I decided for my third hard cheese I would try a manchego type using 1 gallon of milk from my Nigerian goat and 1 gallon of pasteurized, un-homogenized cow milk (the good stuff that comes in the glass bottles at Whole Foods). I am basically following the recipe for the saffron infused manchego in aArtisan Cheesemaking at Home, except that I am not adding saffron and I am using 1/2 packet of the mesophilic culture C101 from New England Cheesemaking and 1/2 packet of their thermophilic culture C201. I pasteurized the goat milk in a double-boiler set up to 145F for 30 minutes, then cooled in an ice bath to about 100F, then I added the (pretty cold) cow milk and after first overheating it to nearly 100F (because I was silly and put it back in the water bath), I cooled the whole thing down to 86F and then added the cultures.
The recipe said to wait 30-45 minutes for a clean cut. It has been over an hour and 15 minutes, and it is just now beginning to (slowly) coagulate. The temp did drop over the past hour from 86F to 84F. So I put it in a water bath and raised and it is SLOWLY coming back up to temp. However, my crude set up with a space heater near the pot did at least keep it steady at 86F for 1 1/2 hrs (ripening time and first 45 minutes after addition of rennet. I made a cheddar and a Havarti this week, and both set like magic.
So... without much experience, and with so many variables changed, I am not sure what is causing the delay and whether or not it is anything I need to worry about. My first cheese was all goat milk, the second, 7/8ths milk from my goat with one quart of goat milk from the store. I pasteurized my goat milk just prior to making cheese in both cases. I used the C101 mesophilic cultures with both prior cheeses with no problems. Given all that, I think I have narrowed it down to either the addition of cow milk, the fact that the cow milk was unhomogenized, adding cold milk to warm milk, the thermophilic culture (that I had not used before), or... I don't know. The rennet is the same calf rennet I used before, and I added the calcium chloride prior to the rennet as before. I did not add lipase.
When I split the packets of mesophilic and thermophilic cultures, I wrapped up the half of each I didn't use together in tin foil and then put it back in the freezer. If it IS the culture, I'd rather know now and order more if I need to.
Any insight is GREATLY appreciated.