In pickling recipes, pickling lime makes pickled foods firmer and crunchier. Pickling lime works by introducing calcium into the pectin of the food. Old-fashioned canning recipes call for pickling lime, including recipes for pickles, green tomatoes and watermelon rinds.
When pickling vegetables, home canners soak the food in a mixture of pickling lime, canning salt and water prior to pickling it. Recipes usually call for soaking the food overnight or for 24 hours and then rinsing it to remove the pickling lime.
Pickles or other foods not properly rinsed after soaking in the solution may cause botulism when consumed. Rinsing the food three times in fresh water is usually sufficient to remove the lime. Grape leaves are a safer alternative to pickling lime and have the same effect of leaving foods crisp.