I am trying to determine the reasoning for the temperature inconsistencies in different recipes of Swiss Meringue Buttercream (I am referring to the type of buttercream where egg whites and sugar are heated over a double boiler, whisked into a meringue, then butter is gradually added):
I have an hotel recipe passed onto me that reads that the egg white/sugar mixture should be heated to 115-120 degrees Farenheit (46 Celsius).
I have also come across recipes that heat to 140 degrees Farenheit (60 Celsius), or even 160 degrees Farenheit (71 Celsius).
I am curious if the higher temperatures cooks/coagulates the whites at all.
I am also curious if the lower temperature is effective at safely controlling bacteria.
For those that have experience with this type of buttercream - what temperature do you cook your whites to?
Thank you for any information at all - it is greatly appreciated!