Every time you freeze whey or milk, you add a couple of extra chances to get stray bugs into your product.
Pour it into a tray, cover it, sit it in the freezer, pop it frozen from the tray and rebag it....
This may not be an issue if you are heating heavily, but if you intend to culture the whey at low temperature (or make cheese from frozen milk) then the chance of contamination increases significantly.
I tried making cheese from frozen raw milk, just an experiment to see if it could be done, and rapidly realised the extra steps mean a lot more sanitising and contamination risk.
Thanks for the response, Fritz... I've bolded the bit above that I still don't get.
Only as an example, poultry products must reach 160⁰F to kill off the beasties (primarily salmonella).
So, given that most of the pathogens that are generally found near or in food products also will be killed at temperatures just slightly higher than this, how is it remotely possible that whey thawed in a refrigerator from a completely frozen state, and then heated to 192⁰F (just 20⁰F below boiling at 1Atm) will have any possibility to have any contamination, unless from a super-bacteria that can survive at near-boiling point heat? I see that you say "may not be an issue if heating heavily" which I presume means over 170⁰F. Is this the exact answer I was looking for?
In any case, making a whey ricotta by the recipe I have, does not use any bacterial cultures, and uses vinegar as a curding agent. So why would bringing up "culturing whey" be necessary? All the rest of that is what is confusing me.
I'm sorry, but I still don't understand.