Alum is used in food preparation to maintain the firmness of pickles, raise the acidic level of some baking sodas and as a crispness preservative in some pickled vegetable and fruit recipes. It is also used to remove snail slime before cooking in Nigeria. During the 1800s, alum was used in England as a bread whitener until it was prohibited by the 1875 Sale of Food and Drugs Act.
Alum in powdered form can be found in grocery store spice sections. Its chemical name is hydrated potassium aluminum sulfate. The term alum also refers to a class of chemical compounds used for a variety of industrial purposes. Used since Roman times as a water purifier, alum also has antibacterial and antiperspirant properties, making it useful in deodorant products. Because it is an astringent, it is used in styptic pencils to help prevent bleeding from small cuts.