Powdered Buttermilk

I have an unusual question but know that someone here will have the answer or good suggestion. 

I would like to use Buttermilk in my bread recipes instead of milk when called for... Since I will most likely not use the whole carton of milk, can Buttermilk be frozen in small, let's say, 1/2 cup quantities without ruining the Buttermilk or flavor? 

My idea is to freeze 1/2 cup Buttermilk(ice)cubes then when I need Buttermilk in a recipe, just remove what I need from the freezer and let thaw.  Does this sound like a good idea?.. 

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