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Cookies For Science.

12.15.2011

I have been struggling recently with the question of how old can baking soda get before it's inappropriate for baking. I decided to do some science - and baked up these cookies last Sunday night.

Chocolate chip cookies with year old baking soda

The above picture shows the cookies made the old baking soda, after having cooled on the rack for about half an hour. They're a little flat; they're tallest where the chocolate chips provide structure for the dough.

Chocolate chip cookies with month old baking soda

The above picture shows the cookies made the new baking soda (sorry for the poor focus). These cookies are puffy; the dough holds it's own structure.

Two cookies, side by side

A cookie with old baking soda is on the left, and a cookie with new baking soda is on the right.

Six cookies, side by side

As before, the cookies with old baking soda are on the left, and the cookies with new baking soda are on the right. The stack on the right is clearly much taller.

The Results

The results were clear to me - the old baking soda delivered a significantly worse cookie. The cookies made with old baking soda were too flat (they were puddles of dough clinging to chocolate chips), and dried out in just 2 days. The cookies with new baking soda were cookie shaped; and still tasty 4 days later. I hereby strengthen my resolve to buy new baking soda every 6 months.

The Recipe

Here is the recipe that I used:

Stir flour, baking soda and salt together. Cream the butter, shortening, white and brown sugar. Add eggs, one by one, to creamed mixture and beat until incorporated, then add vanilla. Gradually mix in flour mixture. Dish rough tablespoons of dough onto a baking sheet and baked for 9.5 minutes at 350° F (until golden brown and delicious). Allow cookies to set on cookie sheets, and to cool on wire racks.

Test Methodology

I prepared two mixtures of 5 5/8th oz flour and 1/2 teaspoon salt, and added 1/2 teaspoon of each version of baking soda to each mixture. I prepared two mixtures of 1/2 teaspoon of vanilla extract and 1 egg for each batch of dough.

I creamed the entire recipe of butter, shortening and both sugars together, weighed the total amount (with the bowl zeroed out), and spooned material out of that bowl until was split in half. While finishing the dough and baking, I stored the creamed mixtures and dough in the refrigerator.

The dough with the old baking soda got proper chocolate chips. I figured this would give them the best chance at being tall; as the chips provided some height. The dough with the new baking soda got chopped bar chocolate, which contributed to its darker color (and did help me to tell the cookies apart.)

Science is re-producible, so I urge you to preform your own experiments!

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