Melba's Jammin' wrote:
> You folks know stuff: What's acidic in a peanut brittle mixture (sugar,
> corn syrup, nuts, vanilla) that would cause it to foam when baking soda
> is mixed in?

Um... nothing?

[You knew I'd come back and lurk briefly on RFC, didn't you? And here
you go, pulling me out of my cave...]

Look he
http://scifun.chem.wisc.edu/chemweek...iumBicarb.html

Specifically, check out the second equation. NaHCO3(s) is sodium
bicarbonate (aka baking soda), the temp of the candy syrup is
sufficient to break it down (you wouldn't need 300 C temps in the
kitchen!), and you produce Na2CO3(s) + CO2(g) + H2O(g) - that is to
say, sodium carbonate, carbon dioxide gas, and water vapor (the s and g
in parens are solid, gas). Carbon dioxide is being released, and you
have the foam trapped in the sugar syrup to make the brittle.

Btw - Matt's not going to see any of your cashew brittle unless I'm
uncharacteristically generous. And I had jam-slathered bread for
breakfast this morning. I'm in heaven!

I wonder also if the tossing in of a fine particulate that doesn't
dissolve would act as nucleation points for boiling (as we discussed
last night with the superheated water!) and would also cause a minor
amount of foam. Wanna make some brittle with talc powder instead of
soda and test out my theory?

> It's assumption on my part that the soda is neutralizing
> acid (I'm thinking about what happens when I add a bit of soda to my
> tomato sauce to reduce it's acidity.)

You're absolutely right about the tomato-acid thing, though. It's still
carbon dioxide being produced but through a different chemical
reaction.

And just for the record, I had to look up the decomposition products of
baking soda. I don't have that kind of stuff memorized.

-j.