Hi. I have yet to make IMBC but want to try it. Is it safe for pregnant women, especially if I use pasteurized egg whites?
Raw eggs can carry bacteria such as salmonella. If eggs have been pasteurized to at least 138 degrees F they are safe. (the website below is one of many for more info). I have made SMBC and IMBC with pasteurized eggs successfully although a few time I had a batch that wouldn't whip.
With IMBC since the hot sugar syrup is poured into the room temp egg whites, and rapidly mixed, there is some controversy as to wether the eggs are heated enough to be considered pasteurized if starting with raw whites. I checked the temperature once and found that after adding the sugar syrup they were well above 138 degrees, but don't quote me! (and don't take chances during pregnancy). Using pasteurized whites of course alleviates that concern. Another option which allows the use of raw eggs (cheaper, and better tasting IMHO) is to make SMBC. I used to make IMBC exclusively, but found that SMBC is easier, and avoids the hot sugar syrup danger and mess. The first step is to heat the whites and sugar in a bowl over hot water (Bain Marie, double boiler, or I just put my mixer bowl on the pot of hot water. I have made a rim of foil to wrap around the pot edge to stabilize it and prevent scratches to my bowl). I bring the eggs and sugar to between 150 and 160 degrees while whisking frequently, which is well above the pasteurization point. One bowl clean up is a plus also. Hope this helps, and Congratulations!!
You could even look up Mike McCarey's SMBC, which is super easy and requires no heat of any kind! It falls between IMBC and American buttercream for sweetness, but tastes like whipped cream!