"Jude" > wrote in message
oups.com...
> Well, today's the big day. My 9 year ld daughter will be baking
> quick-bread all day long for the science fair. We have a recipe for a
> good oatmeal-raiain bread. Her hypothesis is that a combination of
> baking soda and baking powder will produce the highest rise. Our other
> loaves will contain: no leavening; just soda; just powder; and dry
> yeast (not proofed, just dumped in). She's going to measure the height
> of each loaf and also have 3 testers (herself, me, and my BF) taste and
> rate the on a scale of 1 to 10 for lightness or density, chewiness or
> softness and a few other characterisitics. Should be an interesting
> project!
>
> Through her preliminary research, she has learned about how leavning
> agents produce carbon dioxide bubbles which cause the loaf to rise.

Since she has already researched how CO2 is produced, it seems that the
basic design of the experiment is flawed. First of all, the inclusion of
yeast is inconsistent for two reasons. First, it is not a chemical
leavening agent. Secondly, it is not used properly as compared to the
chemical leavening agents since you are not allowing any time for CO2 to be
produced by the yeast. In other words, you have all too many variables to
the experiment and any findings will be inconclusive. If she were older, I
would suggest finding some additional chemical leavening agents to compare,
but this would add too much complexity.

The second issue relates to your (her) assumption that the combination of
baking soda and baking power will have the best results. Unless there are
acidic ingredients, the baking soda will just sit there and produce no
additional CO2. This indicates that neither of you really understand how
CO2 is produced by chemical leavening agents.

A more easy to understand and therefore more educational comparison would be
to make the recipe with no leavening agent, with baking soda only, and with
baking powder only. The first to batches should be the same - flat. This
would show that baking soda ALONE is not a leavening agent. The batch with
baking power should be normal, thus proving you need both an acid and baking
soda (aka BAKING POWDER) for CO2 production. An extension to the experiment
would be to use increasing quantities of baking powder and use some
objective measure like density to measure the optimum amount of baking power
per unit of batter. There is a point where too much leavening agent will
cause the product to collapse and become more dense, not less.