Welcome to the Cake Decorators Q&A
Hi Paul and David.My lovely off white SMBC turns yellow when I put my cake in the fridge. Is there any way to avoid this problem? Once my whole cake colour looked different the next day after putting it in the fridge!
The colour change is due the butter solidifying during refrigeration. A couple of ways to avoid this happening is to use a less yellow butter such as Lurpak or add a food whitener such as Sugarflair icing whitener:
Adding a tiny bit of Sugarflair grape violet to buttercream can also make BC appear more white. Take a peek at the following video by Raewyn Read:
Another way would be to use vegetable fat like Trex or Crisco instead of butter but it wouldn't taste very nice. The taste can be enhanced with the use of butter flavouring. I think Wilton have a vegetable fat 'buttercream' recipe on thier website. To see different brands of artificial butter flavouring, take a peek here:
Hope some of the suggestions help.