Alum may be used in pickling recipes as a preservative to maintain fruit and vegetable crispness. Alum is used as the acidic component of some commercial baking powders. It’s also an ingredient in baking powder (responsible for the faintly metallic taste). In recent years, alum powder has become increasingly difficult to find because it is toxic to humans if consumed in large quantities (more than 1 ounce). Potassium alum has been used in maraschino cherries and pickles. The aluminum helps make the cell walls of fruits and vegetables sturdier, producing a crisp pickle or firm cherry.
Alum powder is often used in vinegar brine for pickles or in homemade (and inedible) modeling clay for kids.
Try making “Sun Dried Potato Chips.” Simply thinly slice potatoes, place slices in water with a pinch of alum powder and soak overnight. Rinse them to remove the extra starch, boil with some rock salt until about 60% cooked. Strain slices in a strainer and spread the thinly sliced potato pieces onto clean cloths on cookie sheets outside in the sun for up to two days. (Fun fact: these dried chips can be stored for up to one year and fried at a later date). Fry in hot oil and sprinkle with red chili pepper! (Or use any dried spices or Niblack Seasoning Blends).
A wonderful way to use alum powder is in a light, crispy, yeasty batch of deep-fried youtiao (long Chinese doughnuts typically served with congee). Recipe after recipe calls for this ingredient, which is essential in creating a crisp crust on this delectable fried treat.
Youtiao (Chinese Donuts)
Youtiao, Chinese Cruller or Chinese doughnut are two long bread sticks attached together made up of flour deep fried in vegetable oil.