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Jan 28, 2007 04:51 PM

Food Scientist alert: What does baking soda do in this recipe?

The Alton Brown in me is dying to know...I made this recpe today, and a lot at Christmas time combining cereal (Quaker Oat Squares), nuts and then a butter-brown sugar-corn syrup mixture you boil then add baking soda and vanilla to. The baking soda makes the butter mixture foam up and turn cloudy. I was just wondering why it did that, and why it was necessary? You then pour the mixture over the cereal and nuts and bake it and it comes out all candied and brown and deliciously addictive! Anyone have any ideas?

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  1. since brown sugar has some molasses it is slightly acidic, and if it was dark corn syrup, then it has molasses as well. The acid would react with the soda to create the bubbles. However, I think that soda reacts at a high tempurature, even in the absence of an acid, but I don't know why this is so.

    1 Reply
    1. re: amkirkland

      "since brown sugar has some molasses it is slightly acidic, and if it was dark corn syrup, then it has molasses as well." Exactly. First time I watched someone making shoo-fly pie he diluted molasses with some boiling water and then stirred in some soda, and it foamed up like crazy. I do not believe that soda would react like this just from heat, but higher temperatures do exaggerate the speed and effect of such reactions as the one between alkaline and acid.

    2. -----

      I believe a statement to be somewhat related. See What is Baking Soda? ; Background ""Its mild alkalinity works to turn up fatty acids contained in dirt and grease into a form of soap that can be dissolved in water and rinsed easily.""

      My hair-brained conclusion is that BOTH the butter and baking soda is there to aid in the water solubility of the sugars. Otherwise the solubility could end up like that of a life saver or a lollipop. In other words making the sugars a soft candied effect, not a hard candy effect.


      1. isn't hard or soft a result of temp sugar is cooked at?

        I know that "foolproof fudge" also has baking soda added to it. In a cook's illustrated articles it said it was to reduce the chocolate's acidity and made a drier, firmer fudge. Similar???

        1 Reply
        1. re: Quine

          Hard candy results from high sugar temp, yes, but filling the sugar full of holes (bubbles) will weaken the sugar matrix, making it crumblier. I've made nut brittle both with and without soda and the kind with soda is noticeably crumblier and easier to bite through and chew. Without soda it is also lovely but you really need to pack it with nuts if you don't want to break a tooth.

          I don't know about the fudge though.

        2. Recipes for ANZAC biscuits (an oatmeal, coconut cookie from Down Under) call for mixing some baking soda with Lyle's Golden syrup (invert sugar). It foams in the same way.


          1. Ditto to most, but here's the science of it...

            ACID + CARBONATE ---> H2O + CO2 + a salt (not necessarily NaCl)

            The CO2 is the bubbles of gas you see that provides leavening. As suggested, the molasses or sugars act as the acidic agent to force this reaction to release CO2. The baking soda is the carbonate actually sodium bicarbonate (Na2CO3), so depending what acid gets used will influence what "salt" gets produced, though it will be some combination of sodium (Na) with another element present in the acid's make-up. Often vinegars or buttermilks are used as the acids.

            5 Replies
            1. re: Emme

              just to be sure, are you saying that molasses is acidic enough to create a significant amount of gas?

              1. re: amkirkland

                it acts as the acid in this recipe... donates a proton... and yes it's acidic enough to break down the Na+ and (CO3)2- bond that will release CO2... it's not a whole hell of a lot of it, bu enough to provide leavening

                and if you had the exact amounts of each used in a recipe, i could calculate for you the theoretical yield of CO2..

              2. re: Emme


                Emme Wrote: ""The CO2 is the bubbles of gas you see that provides leavening.""

                Unfortunately, the process is not about leavening, or as we know of it for a final rise. In other words, the entire leavening process was shot before it could take place, thus the question before us.

                There is no question a gas exchange has happened, but for "what real reason (?)".

                I say the exchange is help in sugar solubility that aids in eating the oatmeal cookie or bar.


                1. re: RShea78

                  I think it's a texture thing, just like peanut brittle. So I think the bubbles stay in.

                  1. re: amkirkland

                    Hence, texture in this case is aided by the "leavening agent,"