I generally use about 1.75 ml of the liquid calf rennet from Mad Millie for my makes with 2 gallons of milk. This tends to give me a flocculation time of 13 to 15 mins. On makes such as feta, where the culture is in the milk for longer, the flocculation tends to be more like 9 mins.
My question involves two makes (a fast cheddar, and a traditional mozzarella) where I intentionally waited for the pH to be 6.4 before adding rennet, and then the flocculation was less than 5 mins. In fact I cannot be sure it was not even faster, because I was not paying enough attention thinking it was not time yet....
However, for 2 other makes of the traditional mozzarella, I also waited for a pH of 6.4, and the flocculation was 9 and 10 mins.
I am not convinced that my pH meter is accurate, and I have started to be more consistent with cleaning and calibrating before each use.
So, is there any suggestion or guideline for decreasing the amount of rennet when working with a lower pH target?