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Speaker 1: Welcome to brain stuff from how stuff works. Hey, brain stuff,

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Speaker 1: Lauren Vogel bomb. Here, let's talk salt. You might toss

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Speaker 1: a little over your left shoulder for good luck, sprinkle

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Speaker 1: some on your eggs, or even tip a shaker into

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Speaker 1: a frothy beer. However you use it, one thing's for certain.

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Speaker 1: Most of us take salt for granted. Salt wasn't always

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Speaker 1: such a simple matter. For centuries, it was a rare commodity,

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Speaker 1: used as payment, as an impetus for wars, and often

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Speaker 1: for survival. Salt preserved fish and ancient Egypt seasoned Roman

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Speaker 1: salad dressings, and even came to stand for a measure

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Speaker 1: of a person's integrity. A competent Roman soldier was worth

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Speaker 1: his salt. He had earned his allowance of the valuable seasoning.

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Speaker 1: But more than being tasty, salt kept entire civilizations alive

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Speaker 1: thanks to its ability to prevent foods from turning into

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Speaker 1: bacterial Latin killers. To understand how salt prevents foods from spoiling,

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Speaker 1: it's important to first grasp how it's used to preserve foods.

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Speaker 1: Salt is used in two primary ways, either in granual

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Speaker 1: form or in brine form. A brine being a water

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Speaker 1: and salt solution. A ham, for example, might be cured

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Speaker 1: with salt, and cucumbers are preserved and turned into pickles

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Speaker 1: with brine. Curing with salt granules, known as dry curing,

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Speaker 1: means applying salt to the outside of a cut of

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Speaker 1: meat and storing it for a couple of days up

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Speaker 1: to several weeks. It's one of the most ancient ways

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Speaker 1: of curing meats. Modern curing can involve injecting meat with

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Speaker 1: salt brine. Whatever the form of salt it's used, the

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Speaker 1: mineral preserves foods and makes them safer to eat by

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Speaker 1: preventing bacteria from growing, including the bacteria that break down

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Speaker 1: rotting food, and also food board pathogens such as salmonella,

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Speaker 1: which can cause food poisoning, typhoid fever, and other serious problems.

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Speaker 1: Salt inhibits bacteria in a variety of ways. It's a

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Speaker 1: disruptor that reeks havoc in microbes, interrupting their enzymes and

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Speaker 1: chipping away at their DNA. It most often works through dehydration,

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Speaker 1: though removing many of the water molecules the bacteria need

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Speaker 1: to live and grow. Water molecules and food are measured

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Speaker 1: in terms of product water activity, a number that signifies

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Speaker 1: the free water molecules present before salt preservation. Many fresh

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Speaker 1: foods have point nine nine product water activity. The product

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Speaker 1: water activity is lowered when salt dehydrates the food through

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Speaker 1: the process of lasmosis. In essence, the salt around the

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Speaker 1: outside of the food draws water molecules out and replaces

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Speaker 1: them with salt molecules until the amount of salt is

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Speaker 1: equal inside and out, Lowering the water product activity to

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Speaker 1: point nine ford to point nine one is usually sufficient

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Speaker 1: to prevent most bacterial growth. Today's episode was written by

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Speaker 1: Laurie L. Dove and produced by Tristan McNeil. For more

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Speaker 1: on this and tons of other salty topics, visit our

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Speaker 1: home planet, how stuff works dot com.