Sodium chloride (NaCl), or common table salt, was among the primary food preservation tools used by ancient humans and its antimicrobial properties are well documented.

Characteristics and Properties

NaCl is used extensively as a nutrient vehicle (typically supplemented with 0.006–0.01% potassium iodide), flavoring or curing agent, and dough conditioner (IOM, 2003). The antimicrobial action of NaCl involves cellular dehydration resulting in growth inhibition of most pathogenic microorganisms by ≤13% NaCl. Secondary inhibition may follow the extraction of extracellular nutrients and available water (lowering aw ) from the surrounding environment.

In one study, McKellar (1993) found that sublethal levels of NaCl in tryptic soy broth interfered with the ability of L. monocytogenes to secrete the toxin listeriolysin O. Advances in food preservation techniques, such as refrigeration, vacuum-packaging, and the use of other antimicrobial ingredients have minimized dependence on NaCl as a preservative. Modern health concerns and the unpleasant sensory effects associated with excessive amounts of NaCl also discourage its use at concentrations sufficient for its autonomous control of microbial populations.

However, when used in conjunction with other additives, NaCl further reduces aw and inhibits salt-sensitive microbes. Enhanced activity is observed in the presence of benzoates, nitrite, sorbates, phosphates, spices, liquid smoke, and various antioxidants (Sofos, 1984) . Previous heat treatments, storage under refrigeration, and low pH may also increase the sensitivity of microorganisms to acceptable levels of NaCl.

Applications

The ability of NaCl to control spoilage organisms has been thoroughly investigated and is well accepted . Most spoilage and pathogenic microorganisms are unable to tolerate the levels of NaCl in fermented meat product formulations, while LAB proliferate in the absence of competition (Sofos, 1984) . Levels required for inhibition are generally lower at refrigeration than at ambient temperatures, although the bactericidal effects of NaCl may be enhanced at higher temperatures. Pelroy, Peterson, Paranjpye, Almond, and Eklund (1994) found that the effectiveness of sodium nitrite and NaCl combinations against L. monocytogenes was affected by inoculum level, packaging conditions, time, temperature and concentration of NaCl (3% vs. 5%). Sodium nitrite plus 5% water-phase NaCl was the most effective combination.