Two expiration dates worth checking before baking a cake
Baking powder and baking soda can expire without being noticeable to the naked eye, and both determine whether the cake rises.
Everyone loves cake, and to make it turn out well, it's best to follow the recipe exactly. According to Wired, too much or too little of any ingredient can ruin the dessert: too much flour makes it dense or dry, and too little makes it sink. According to Southern Living, the texture suffers if the ingredients aren't combined well. A perfect cake has a uniform, moist crumb, is golden brown and tender, and holds frosting well.
Two ingredients are key to these characteristics, and both have expiration dates that should be checked. Baking powder is a combination of acid and base that, when mixed with liquid, produces carbon dioxide and makes the cake rise. Baking soda is a base that, with an acid like lemon juice or buttermilk, produces the same gas. Both are sensitive to humidity, which reduces their effectiveness over time.
According to the USDA, baking powder typically lasts about three months after opening, although Utah State University indicates it can last up to 24 months if stored in a cool, dry place. Most packages have an expiration date. For added safety, it's a good idea to note the purchase date and replace the baking powder a year later. According to Martha Stewart, baking soda lasts about six months after opening. Baking soda doesn't spoil, but over time it loses its ability to produce gas due to moisture absorption.
If the baking powder has been transferred to another container, the date will usually be lost, but there are home tests. David Lebovitz recommends mixing the baking powder with boiling water: if it bubbles vigorously, it may still be fresh enough. For baking soda, according to the Los Angeles Times, put a teaspoonful in a little vinegar, carefully, because it may bubble vigorously; if it does, it should still be good. Clabber Girl, which makes a double-action, aluminum-free baking powder, cautions that bubbles in water aren't enough to tell if the powder is old.
For a cake for an important occasion, if there is any doubt about the date, it is wisest to buy new baking powder and baking soda.
