This comes to us from a local Eugene Chapter member.  The New York Times recently had an article on real buttermilk:

“Many home cooks keep buttermilk on hand for pancakes, ranch dressing or corn bread. They might know that it makes more tender cakes (because it softens the gluten in flour), loftier biscuits (its acid boosts leaveners like baking soda and baking powder) and thicker dressings (lactic acid in buttermilk gently curdles proteins into a smooth mass).

But what few cooks know is that commercial buttermilk isn’t really buttermilk. It is made from regular low-fat or skim milk, usually low-grade rejects from cheese and butter companies. The milk is inoculated with cultures to make it acidic, and thickened with additives like locust bean gum and carrageenan. The result is a flattened facsimile of the real thing, as a ring tone is to a song.”

Read the whole article here: http://www.nytimes.com/2012/09/12/dining/buttermilk-often-maligned-begins-to-get-its-due.html