I know this topic is not exactly 'hot' anymore, but I still want to contribute to this discussion. All you've talked about is milk, but the phenomenon of food reacting to thunderstorms is not limited to that fluid. Try making mayonnaise, bread dough or stock: a waste of effort.

Explanations I've heard (but no one could mention reliable sources) vary from thunderstorms (the air itself turns 'sour' - low PH) and anaerobe bacteria to women having their period.

That it happens, is not a matter of discussion, it does. It's not a fable from the distant past. So, suggestions anyone?