Has anyone tried to pasteurize their egg whites for royal icing? Like heating the egg white in a double boiler until it reaches 140F - 160F, then cooling it before using it for the royal icing. Would this still work, even if it is heated? I am thinking that it is since meringue powder is spray dried which uses heat as a medium of drying, please do correct me if I'm wrong. 

Another question; is it safe health-wise to really boil condensed milk in the can? I've read some articles (and vaguely remember being taught in my Food Technology course) of cans used in canned food containing chemicals that are carcinogenic and affects testosterone/estrogen levels which are released into the food when heated. Is there any other way to make dulce de leche?

a) yes, I'm doing that with egg whites. Just done some pavlova for a lunch at a friends house and I heated the egg whites before making the meringue.  Call me crazy but I feel better serving people something DEFINITELY NOT containing salmonella. 

b) I once tried the can in pot method but am not a huge fan. Sounded easy to make. Also tried the oven method (that might be something for you since you remove the content of the tin into an oven dish - foil -water bath - done). But honestly I'm sticking with the good old tradition of making it from scratch in a pot with milk and sugar ; ) Takes longer but it's worth it I find.