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.
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.
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.
A cookie with old baking soda is on the left, and a cookie with new baking soda is on the right.
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 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.
Here is the recipe that I used:
- 11 1/4 oz all purpose flour
- 1 teaspoon baking soda
- 1 teaspoon salt
- 1/2 cup butter (room temperature)
- 1/2 cup shortening
- 3/4 cup granulated sugar
- 3/4 cup packed brown sugar
- 2 large eggs
- 1 teaspoon vanilla extract
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.
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!
I received a subscription to Cook's Illustrated for my birthday last year, an excellent instructional magazine for cooks.
For each recipe, Cook's Illustrated first devotes an entire page (sometimes two) to the challenges that the author overcame in developing and testing this recipe, which I initially thought was all worthless jibber-jabber. I've since realized that the whole point of the play-by-play recipe evolution story is to tell me why certain arcane steps are necessary. By more fully engaging my brain, it's helping me not to skip a step in the process they've outlined. By involving me, I learn.
Another huge advantage of Cook's Illustrated is that the authors are always kind enough to always provide the weight equivalent for flour in baked good recipes.
When baking, I prefer to measure flour by weight rather than by volume, particularly when measuring flour. The best results come from the precise and repeatable measurement of ingredients that measuring by weight delivers. Measuring by weight is also much faster - since I don't have to fiddle around with sifting or leveling off the cup. The only difficulty was in converting the volume-based measurements called for in most recipes into a weight for my kitchen scale.
For a while, I would simply equate a quarter cup of flour to one ounce of flour. Then I came to the conclusion that my cookies were simply not as puffy as they should have been; shown in the left of this picture. They had a crispy outside, but were missing a softer inside.
I looked through The Fannie Farmer Cookbook, I'm Just Here for More Food, and several issues of Cook's Illustrated to compile the table below. After using the conversions in this table, I was rewarded with the much softer, puffier cookies; shown at the right of the above picture.
|12 1/2 oz
||2 1/2 cups
|2 1/4 cups
||11 1/4 oz
||9 1/2 oz
|1 1/2 cups
||7 1/2 oz
See this chart for more detail.