Yeast is a living organism that needs time to develop and multiply in a
dough mixture. As it develops, it produces carbon dioxide gas. In
order for yeast to make dough rise, the dough has to have a certain
amount of gluten developed so that it can stretch and support the
bubbles of CO2 produced by the yeast. If the dough mixture is too thin
(more like batter), the gas bubbles will simply rise to the surface and
dissipate, like champagne bubbles. If there's not enough gluten, the
same thing happens. Typically breads that rely on baking powder rather
than yeast don't have enough gluten (usually provided by wheat flour) to
support the slow yeast-driven rising process.

Baking powder is a combination of chemicals that produce gas when
moisture is added. Usually it is added to a bread batter with the other
ingredients, and baked almost immediately. So it is still producing gas
as the batter begins to set up during baking, causing some of the gas to
be trapped in the batter as it solidifies, making it rise mostly in the
oven. Gluten content of the batter is much less of a factor than is
simply having the "right" amount of baking powder for the batter
mixture.

Bob
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In article <sAQ6h.4889$T_.684@trndny06>, says...
> Given a piece of bakery, how can you tell if it was made with yeast or
> baking powder?
>
> I want to be able to do this in order to make things that I don't have
> receipe for.
>
> Let me make a first attempt: if there are large, uneven bubbles inside, then
> it is made with yeast. If the texture is even and spongy, it is made with
> baking powder/soda. Right?
>
> Using this guide, that I would guess that corn bread is made with baking
> powder. But why? Afterall, shouldn't bread be made with yeast, by
> definition??
>