Alum is a salt that has a variety of industrial uses. It is an ingredient in baking soda. It is a preservative and is good for fermented foods like pickles. Alum is also added to maraschino cherries to make them crisp and delicious. Regardless of its culinary uses, alum is a safe and useful ingredient in the kitchen.
It is widely available in grocery stores and can be purchased online, but it must be in crystal form. If you purchase alum in powder form, make sure to store it in an airtight container. For best results, store the powder in a dark, cool area.