Sodium chloride decreases the water activity of foods, thus helping to control the growth of pathogenic bacteria. Sodium chloride this used as a preservative in meats and is necessary to make fermented products.
Since microorganisms require water to survive, they cannot exist when their water requirement is diminished by the addition of salt. Amount of water can be reduced availability to microorganisms by lowering the water activity (aw).
Water activity is an excellent stability factor for microbial growth, because the creation of osmotic pressure difference between the hydrated microbial cell and the surrounding food leads to cessation of microbial growth.
Microorganisms require high levels aw. Most bacteria require a minimum aw level of 0.96, although halophilic bacteria can grow at a aw of 0.75.
Most yeasts grow at aw levels of 0.90 and above, although a few can grow at a aw level of 0.81. Mold grow at lower aw levels with some able to grow at a aw level of 0.62. While salt preserves foods mainly by lowering the aw, the chloride ion is believed to inhibit bacterial growth independently.
Sodium chloride as food additive
