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Pickling lime is an ingredient used in the pickling process to preserve vegetables such as cucumbers. The purpose of food-grade lime is to preserve the pickles’ firmness, and a similar firming agent, alum, is sometimes used instead of lime in some pickling recipes. Calcium hydroxide, another name for pickling lime, is combined with water to make a soak for cucumbers in many pickling recipes, and the soaking period can vary from 12 to 24 hours. Following this time period, however, it is essential that all lime be washed away from the food that is being pickled, whether it is pickles or watermelon rinds or some other type of produce. Failure to do so could lead to botulism, a nerve toxin that causes severe illness and sometimes paralysis and death.
Food safety experts recommend that pickling lime and alum be discontinued as firming agents in pickling recipes, despite their use as ingredients in generations of pickling recipes. Experts say that pickling lime and alum can be harmful. Alum is deadly if an adult consumes a total of just 1 ounce (28.34 grams), and lime can cause botulism as well as other serious health problems that also could result in death. If pickling lime is used in a recipe, the cucumbers or other vegetables being pickled must undergo a number of rinses with clear water to wash the lime away. Extra rinsing is necessary because the vegetables being pickled can absorb some of the lime from the pickling mixture the vegetables were first soaked in.
Safety recommendations call for an initial water rinse or soak for one hour, and then two more similar rinses immediately following the first. To avoid the use of pickling lime, an alternate way of firming cucumbers before pickling is to immerse the cucumbers in cold water and leave them soaking for up to five hours. Another recommendation is to make sure all vegetables to be picked are as fresh as possible because any hint of softness or spoilage cannot be reversed.
Industrial grade lime is not recommended for use as a pickling lime because it may contain impurities that are not safe for ingestion or use with food. Industrial lime can be found in cleaners, solvents and cement. In addition to botulism, lime ingestion can cause calcium hydroxide poisoning with numerous symptoms that require medical attention, including throat pain, vision loss, digestive problems that include vomiting and pain, organ damage, breathing trouble, skin burns and a rapid drop in blood pressure.