SALT AS PRESERVATIVE - Table salt or sodium chloride is a common preservative because it is non-toxic, inexpensive, and tastes good. A high concentration of salt kills organisms that decay food and cause disease. A concentration of 20% salt will kill bacteria. Lower concentrations inhibit microbial growth until you get down to the salinity of the cells, which may have the opposite and undesirable effect of providing ideal growing conditions.

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Salt As Preservative

How Does Salt Preserve Food?

by Anne Marie Helmenstine, Ph.D. 

Salt draws water out of cells via the process of osmosis.

Essentially, water moves across a cell membrane to try to equalize the salinity or concentration of salt on both sides of the membrane.

If you add enough salt, too much water will be removed from a cell for it to stay alive or reproduce.

A high concentration of salt kills organisms that decay food and cause disease.

A concentration of 20% salt will kill bacteria.

Lower concentrations inhibit microbial growth until you get down to the salinity of the cells, which may have the opposite and undesirable effect of providing ideal growing conditions.

Other Chemical Preservatives

Table salt or sodium chloride is a common preservative because it is non-toxic, inexpensive, and tastes good.

However, other types of salt also work to preserve food, including other chlorides, nitrates, and phosphates.

Another common preservative that works by affecting osmotic pressure is sugar.

Salt and Fermentation

Some products are preserved using fermentation. Salt may be used to regulate and aid this process.

Here, salt dehydrates the growing medium and acts to maintain fluids in the yeast or mold growing environment.

Uniodized salt, free from anti-caking agents, is used for this type of preservation.

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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https://www.thoughtco.com/why-does-salt-work-as-preservative-607428