Flashbacks to my first post in this forum... bad memories :-P (still feel bad about that interaction...). But, yeah, it shouldn't matter. You just have to get it dissolved before you add the rennet. CaCl2 is plenty soluble enough that it will dissolve well at any temperature you will want to add it (which is why we use it...) The *only* thing it does in cheese making is to add calcium ions so that the casein protein will have something to use to stick together. Usually not necessary in raw milk because there is usually enough dissolved calcium. The only reason you need it in pasteurised milk is because calcium phosphate (which is what is in milk) has a *lower* solubility as the temperature rises (opposite of what you might expect, but similar to many other calcium salts like chalk or gypsum). When the milk is heated to pasteurise it, the calcium comes out of solution. Calcium chloride has a *higher* solubility as the temperature rises, so by using that you can ensure that there is enough dissolved calcium in the milk.
