"chembake" > wrote in message
oups.com...
>
> Scott wrote:
> picked up a copy of Baking 9-1-1 by Sarah Phillips,
> <http://www.amazon.com/exec/obidos/tg/detail/-/0743246829/qid=11268086...>
>
>>and came across a statement that piqued my interest. In her recipe for
>>sugar cookies, she writes "most cookies use baking powder for leavening;
>>I chose to use baking soda. It causes the cookies to spread rather than
>>puff, perfect for a crispy cookie, and have a wonderful buttery flavor
>>you can't get with baking powder."
>
> Baking soda in the absence of any acid salt will make the cookie dough
> slightly alkaline. Now alkaline conditions will alsoto promote
> Maillard's reaction promoting the formation of flavors.
>>The ingredients a unbleached AP flour, baking soda (1/2 tsp), baking
>>powder (1/4 tsp), salt, unsalted butter, sugar, an egg, vanilla extract,
>>and an optional 1/2 tsp lemon extract.
>>First, what could the acid be? What would interact with the baking soda?
>
> If baking soda is heated:
> 2NaHCO3 ( heat) = Na2CO3 + H2O + CO2, it does not need any acid to
> release the gas which can contribute some leavening action.
>
>>If nothing, why add baking soda?
>
> It is added primarily to generate CO2 but it has other effect on the
> cookie dough also.
> Baking soda is used alone in some cookie formulation but in my
> experience is not the best leavening salt; I prefer ammonium
> bicarbonate instead as it can produce more gases per molecule of the
> salt
> NH4HCO3 ( heat) = NH3 +CO2 + H2O
> Therefore for every molecule of ammonium bicarbonate it releases three
> molecule of leavening gases; ammonia, carbon dioxide, and steam .
> Where as two molecules of baking soda as shown above will only release
> a molecule each of carbon dioxide and steam.. Therefore in per molecule
> basis ( NaHCO3)its not efficient. Besides the sodium ion has a
> tightening effect on the protein due ionic bonding with the amino acids
> in the protein molecule which can confer some stabilizing effect .
> Now if the thesis is cookie spread, the reason for that is the cookie
> dough alkalinity which will tend to loosen the gluten structure but not
> much exhibited by baking soda actually.
> The pH of the ammonium bicarbonate leavened cookie is slightly higher
> and so promote more dough relaxation allowing it to spread better
> resulting in flatter cookie with wider diameter than the ones leavened
> with baking soda.
> As the ammonia does not form a tigher ionic bond than the sodium oon
> the cookie texture is more loose and so tends to spreads more.
> The only advantage of baking soda against bicarbonate of ammonia (
> baking ammonia) is that it does not leave any ammoniacal smell to the
> cookie.
> But I don't see that the spread factor( the ratio of the cookie
> diameter to its height is significant with baking soda and that can be
> influenced also by the amount of fat present in the recipe as well as
> the nature of the flour used.
>
> >Second, it DOES have baking powder,
>
> That is self explanatory, baking soda alone does not leaven the cookie
> dough efficiently but needs a boost from the baking powder. Besides it
> needs a higher temperature for the baking soda to evolve the needed
> carbon dioxide so if used alone and baked at moderate baking
> temperature you will not get what you expect in terms of leavening
> performance.. In addition the reaction of baking powder once its
> hydrated allow for the formation of some gas cells which are expanded
> by the released steam and CO2 from the oven heat release of baking soda
> and from residual amount of baking soda in the baking powder
>
>>too, so what's she talking about about choosing to use baking soda?
>
> I would say that her selection is opinionated based upon her limited
> experience in chemical leavening application .. If she happened to be
> well experienced and more knowledgeable with the chemistry of
> leavening agents she should not say that! I
>
>>know that some recipes use both, but (a), baking soda is often used to
>>also neutralize an acid,
>
> You are right, baking soda is used in baking with acidulant for the
> efficient release of the carbon dioxide
>
>>and (b) she seems to imply she was substituting
>>one for the other. OK, maybe that's a nitpick
>
> Her employment of two CO2 generating agents is due to the fact that
> with a slightly alkaline dough due to the formation of sodium carbonate
> will promote the cookie to brown faster resulting in a nice cookie
> color if baked at just moderate temperatures. If she is only employing
> baking powder it will appear to be pale colored as the slightly acidic
> dough does not promote the cookie crust to brown .
> Besides the crumb color will be not pale colored as well for the same
> reason.
>
>> Third, by saying that
>>baking soda makes the cookies spread rather than puff, doesn't that mean
>>it ISN'T a leavening agent here?
>
> I have already stated above the reasons for spreading . but its
> presence will add a bit more of CO2 to added baking powder.
>
>> And finally, how on earth would baking
>>soda add "a wonderful buttery flavor"???
>
> It is self explanatory,s the uses butter here which when it heated
> volatilizes the aroma components , and is the main source of butter
> flavor.
> But it does not hold if you use a bland tasting fat in the dough and I
> had confirmed thate extensively in the past.
> Butter flavor can arise if you use substances that contains it such as
> added butter flavor, the use of some margarines and surely of pure
> butter and anhydrous milk fat.
> Even the use of full cream milk and buttermilk seems to generate the
> buttery aroma also in cookies.
> I have used baking soda /baking powder tandem in the past to leaven
> some cookies containing vegetable shortening and I get a different
> smell , artificial and unappetizing more soapy in character. These is
> due to minimal fat breakdown resulting in the release of fatty acids
> which will combine with the sodium ion to forms soapy tasting cookie
>


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