Cupcake connoisseurs know a great cupcake is tasty and moist, with a fluffy texture, and a perfectly round, dome-shaped center. Practice makes perfect and if your cupcakes don't yet thrill the senses, give your baking skills time to grow. Some fresh baking soda used as a leavening agent can make your cupcakes rise higher than the rest. Use an old box of baking soda and your cupcakes could be a flop.
1. Carbon Dioxide
Adding baking soda to your recipe makes your cupcakes light and porous by increasing the surface area of the batter. A chemical reaction between baking soda and whatever acid you add to your recipe -- buttermilk, sour milk, lemon juice, cream of tartar or molasses -- forms carbon dioxide when heated. The more carbon dioxide the baking soda produces, the higher your cupcakes will rise. Old baking soda will not produce the same amount of carbon dioxide as a fresh batch.
2. Flat Cupcakes
After a while, baking soda begins to lose its oomph. This will be worse if the baking soda is not stored in an airtight container, notes Joshua Trent, in his book “500 Uses for Baking Soda.” Using baking soda that is too old will result in flat, dense cupcakes that do not rise to the heights they should.
3. How Old is Too Old
When stored at a temperature of 70 degrees Fahrenheit, the average shelf life of baking soda is two years, notes Kansas State University Agricultural Experiment Station and Cooperative Extension Service. If the box of baking soda is open in your cupboard, the shelf life may be less. If the baking soda is stored in your refrigerator -- old, expired or only a week-old box -- do not use it in your cupcakes. You are better off buying a new box to ensure your cupcakes rise and do not take on the odors the baking soda picked up during its stint in the refrigerator.
4. The Test
If you worry your baking soda may be too old to add to your favorite cupcake recipe, perform the freshness test. Remove 1 1/2 teaspoons of baking soda from the carton and pour it into a small bowl. Measure 1 tablespoon of white vinegar and pour it on top of the baking soda. If the baking soda begins to fizz, it will work as an effective leavening agent.