Salt as microbial inhibitor

Salt is an excellent microbial inhibitor, mainly due to its suppression of the water activity of the material to which it is added. Its effectiveness is enhanced when the food is also dried or smoked or both. Smoking also imparts a partial preservative effect.

The early food uses of salt were for the purpose of preserving meats. This use is based on the fact that at high concentrations, salt exerts a drying effect on both food and microorganisms.

Salt can act in several ways to inhibit microbial growth and thus preserve the food. Perhaps most important, it reduces the amount of water available to micor0rganism for growth processes. Water activity (aw) is term used to express numerically degree to which water in foods is available to microorganisms.

The use of salt as a preservative serves to inhibit microbial growth by reducing the water activity and increasing the osmotic pressure of the food.

Salt (saline) in water at concentrations of 0.85-0.90% produces an isotonic condition for non-marine microorganisms. Because the amounts of NaCl and water are equal on both sides of the cell membrane, water moves across the cell membranes equally in both directions.

To damage microbial enzymes, NaCl must gain access to the intracellular pool. Enzymes can be damages in a variety of ways by high ionic environment and perhaps by NaCl specifically. Many of those involved in the preservation effect of NaCl are involved with cellular recovery from stress.
Salt as microbial inhibitor