Welcome to brain stuff from how stuff works. Hey, brain stuff, Lauren Vogel bomb. Here, let's talk salt. You might toss a little over your left shoulder for good luck, sprinkle some on your eggs, or even tip a shaker into a frothy beer. However you use it, one thing's for certain. Most of us take salt for granted. Salt wasn't always such a simple matter. For centuries, it was a rare commodity, used as payment, as an impetus for wars, and often
for survival. Salt preserved fish and ancient Egypt seasoned Roman salad dressings, and even came to stand for a measure of a person's integrity. A competent Roman soldier was worth his salt. He had earned his allowance of the valuable seasoning. But more than being tasty, salt kept entire civilizations alive thanks to its ability to prevent foods from turning into
bacterial Latin killers. To understand how salt prevents foods from spoiling, it's important to first grasp how it's used to preserve foods. Salt is used in two primary ways, either in granual form or in brine form. A brine being a water and salt solution. A ham, for example, might be cured with salt, and cucumbers are preserved and turned into pickles
with brine. Curing with salt granules, known as dry curing, means applying salt to the outside of a cut of meat and storing it for a couple of days up to several weeks. It's one of the most ancient ways of curing meats. Modern curing can involve injecting meat with
salt brine. Whatever the form of salt it's used, the mineral preserves foods and makes them safer to eat by preventing bacteria from growing, including the bacteria that break down rotting food, and also food board pathogens such as salmonella, which can cause food poisoning, typhoid fever, and other serious problems. Salt inhibits bacteria in a variety of ways. It's a disruptor that reeks havoc in microbes, interrupting their enzymes and
chipping away at their DNA. It most often works through dehydration, though removing many of the water molecules the bacteria need to live and grow. Water molecules and food are measured in terms of product water activity, a number that signifies the free water molecules present before salt preservation. Many fresh foods have point nine nine product water activity. The product water activity is lowered when salt dehydrates the food through
the process of lasmosis. In essence, the salt around the outside of the food draws water molecules out and replaces them with salt molecules until the amount of salt is equal inside and out, Lowering the water product activity to point nine ford to point nine one is usually sufficient to prevent most bacterial growth. Today's episode was written by Laurie L. Dove and produced by Tristan McNeil. For more on this and tons of other salty topics, visit our home planet, how stuff works dot com.