<<Disclaimer:  Verify this information before applying it to your situation.>>
 
Ginny,
  recipes calling for buttermilk are usually relying on the acid in it to
react to the base (backing soda) to make the batter rise. An old cook's trick
is to add a spoon of vinegar to sweet milk to make it acidic. The same trick
should work with soy milk.
Pam
[log in to unmask]