Ed Bechtel wrote:
> Jeff Miller wrote:

> > buttermilk. I've done some searching, but haven't found anything that really explains why
> > that might be -- anyone have an idea? Or am I deceiving myself again that buttermilk might
> > be the culprit? Adding buttermilk to whole wheat sourdough just seems silly, but, what do I
> > know?)
>
> Ed Bechtel replies:
>
> Jeff, buttermilk is like a single acting baking powder. I don't know
> why. In the old days, they didn't have baking powder. One would keep a
> jar of clabbored milk (sp) on the back of the stove which was just
> fresh milk that sat around and soured. Or one would use buttermilk. Or
> one would use milk with a little vinegar added. In either case things
> like biscuits, pancakes, or quickbreads would use the sour milk and
> maybe a pinch of baking soda (not powder) to achieve the rise. Sounds
> like your yeast breads work so quickly that the buttermilk rise is
> still active and giving some assist.
>
> By the way. Biscuits or muffins made with just buttermilk and no baking
> powder are the best - you should try them.

Alton Brown covers why you get extra rise wih butter milk (an acid) and
baking soda (an alkaline). Ever seen a bottle rocket? From Altons show:

AB: I mean, so's ... so's that chicken there. I mean, come on. You guys
need to get your mind right on buttermilk. Everyone gather around while
I preach some, okay? Now, pay attention. In the good ole days,
buttermilk referred to the watery, whey-like liquid leftover from
butter churning. It really wasn't good for much of anything. But
today's buttermilk actually has more in common with sour cream or
yogurt than its ancestor over here. See, low fat or skim milk is
inoculated with a bacterial culture. Now these little beasties eat some
of the lactose and turn it into tangy lactic acid, right? Now when the
acid reaches a particular level, the milk is heated, the bugs are thus
dispatched and that leaves buttermilk. Now, bakers love this stuff. Not
only because of its trademark twang, but because a cup will neutralize
a quarter teaspoon of baking soda thus providing sufficient CO2 to lift
one cup of flour. Okay, any questions?

http://www.goodeatsfanpage.com/Seaso...Transcript.htm