I use it ALL the time. I buy it at
Ultra Foods in Forest Park, but I don't remember ever having trouble finding it at Jewel. Look by the baking section, near the condensed milk. Looks like this
I use it most often in muffins, but it works for almost any baked goods recipe that call for buttermilk or sour milk. Just note that you don't re-hydrate it. You mix it in with the dry ingredients and then add the additional water to your wet ingredients.
More information about powdered buttermilk from the Saco website
here. When your great-grandmother prepared her special baked goods with buttermilk, she knew they would be light and tender every time. From experience she had learned that the golden flaked, tart liquid leftover from butter churning made a definite difference in the texture and volume of her finished products.
Most of the buttermilk-based recipes you find today were originally formulated around real buttermilk, not the cultured skim milk product available in the dairy case today. Fluid "Cultured Buttermilk" is not really buttermilk! It is a cultured skim milk that does not have the same properties as real churned buttermilk.
SACO Foods, Inc., a Wisconsin-based dairy product firm, developed a Cultured Buttermilk Blend for consumer use made from real sweet cream churned buttermilk -- the by-product of Wisconsin butter making. It was, and still is, the first real buttermilk available to the consumer in nearly 50 years.