Can someone please tell me what the purpose of meringue powder is? I always thought it was necesary to use it to make the buttercream crust but now I'm not so sure. I use the Wilton class buttercream recipe which is ok but will it crust without the meringue powder added?

You can use meringue powder to make royal icing and colorflow, instead of using real egg whites. I don't know if the wilton class icing crusts...it's been awhile But if you search for "crusting buttercream" in the recipes on this site, you will find a ton of awesome recipes, and none of them call for meringue powder. I don't ever use meringue powder in my buttercream, and it crusts beautifully. HTH

The Wilton class recipe will crust w/o meringe powder. I always thought the reason some people use it in icing was to help keep the colors from bleeding. Not sure about that though.

When taking the Wilton classes, I also used the recommended meringue powder in the Wilton (crusting) Class Buttercream recipe.

(Now I don't use that recipe.) But I did make it without the meringue powder and didn't notice a significant difference in the crusting.

Here's some info I found on using meringue powder for Royal and other cookies icings that result in a firm "shell":

http://www.preparedpantry.com/meringue-powder-royal-icing-frosting.aspx

Same info for Wilton meringue powder, which in additions says that the meringue powder contains "binders" to keep other ingredients from separating:

http://www.epinions.com/review/Wilton_Meringue_Powder_706_6007/content_115399298692

Personally, in an American b/c (crusting or not) I don't know how a Tablespoon or so of meringue powder is going to make a significant impact in the "binding" properties.

HTH

Meringue powder is essentially a replacement for egg whites. It's only practical application is in making royal icing or color flow. As for it's uses in Wilton's buttercream, it's purpose is to make Wilton money.

Thank you all so much for your replies...I was sort of beginning to think maybe it didn't really have a purpose in the buttercream. Next time, no MP...save that money!

The Wilton class BC will crust w/o the meringue powder. But I use it in my BC frosting because it seems to make it lighter and fluffier if blended long enough (like whipping egg whites to make the topping for a meringue pie). It changes the consistency enough that less water/milk is used in the BC and you don't taste the 10X sugar as an independent flavor. JMHO