Why salt is used for preservation?

Protection of foods from microbial spoilage using salt (usually sodium chloride) or sugar (usual sucrose) has ancient roots and is often referred to as salting, salt curing, corning, or sugar curing.

Salt has been used as a preservative for ages, and works to preserve food in two ways:

• Salt dries food. Salt draws water out of food and dehydrates it. All living things require water and cannot grow in the absence of it, including the bacteria which can cause food poisoning.
• Salt is effective as a preservative because it reduces the water activity of foods. The water activity of a food is the amount of unbound water available for microbial growth and chemical reactions.