Salt acts as a preservative by inhibiting microbial growth. Salt acts by drawing water out of the cells of foods and bacteria through a process known as osmosis.
Reducing the amount of water available to bacteria inhibits or slows bacterial growth and reproduction. High concentrations of salt can also rupture bacterial cells due to differences in pressure between the outside and inside of the microorganism.
Salt is also effective in protecting foods against moulds and yeast- it prevents the fermentation of yeast and the growth of moulds by reducing water supply. Vegetables are generally preserved by pickling them in a salt and water solution brine , while meat may be rubbed with salt and dry cured or may be injected with a salt solution. Most often foods must be preserved in much lower salt concentrations to retain the desirable qualities of the food. The moisture content of the food is, therefore, a critical aspect of how likely the food it to spoil in a short time frame.
We know then that by reducing the moisture content of foods we can inhibit microorganisms from growing and therefore extend the shelf life of the food. Dehydrating works on this same principle, many types of food such as fruits, vegetables, meat and fish is dried. Ancient ancestors in the right climates would have dried meat in the sun to save food from a hunt. In areas where the climate is not suitable to dry foods in the sun, our ancestors would have has to come up with a different method of dehydrating the food, salt was one of these ways.
The mechanism that is in effect when we salt foods to preserve them is osmosis. Osmosis works by drawing water across a cell membrane so that both sides have an equal amount of saltiness or salinity. Salt not only draws water out of food but also draws moisture out of any bacteria or microorganism that is on or in the food killing them in the process. When we cure foods with salt it can either be done by applying actual salt granules to the food or via a brine that the food is immersed in.
Both processes draw moisture out of the food to dehydrate it but some applications work in slightly different ways that affect how the food is preserved. The fish will last several months in the fridge longer than it would without the salt.
The same process can also be done with coarse salt without the brine. But additional features about these foods, such as dehydration beef jerky or addition of acid pickles or preservatives ham , help prevent spoilage. In addition, many salt-preserved foods require refrigeration after opening in order to slow microbial growth.
For most edible foods, the answer is no, a higher salt concentration doesn't help keep your food fresh unless you want to risk getting sodium poisoning. Did you know that bacteria grow best in conditions saltier than most foods we consume?
Even if salt was a good preservative, would it be a good idea? It's thought that the salt content of the Western diet is contributing to poor health, including kidney disease. From heart disease to autoimmune disease, to osteoporosis , learn why you may want to throw away the salt shaker to live longer. There seems to be plenty of evidence that salty foods aren't microbe proof foods.
That said, anyone asking these questions and learning about food safety is a very wise consumer. Food poisoning is common. The Centers for Disease Control and Prevention CDC estimates that annually 48 million people 1 in 6 get infected by a foodborne illness, , are hospitalized, and 3, die.
While salt isn't the solution, there are many things you can do to keep your food safe. First of all, practice good kitchen safety. Never use the same cutting board for raw meat and vegetables or fruits. Buy foods well before the expiration dates. Even if a food is not expired, if the smell is suspect, throw it out. Stay up to date on the news to hear of any food-poisoning outbreaks. Avoid unpasteurized milk to reduce your risk of milk-borne infections. Refrigerate foods promptly after eating and use safe food-storage practices.
Heat foods thoroughly when re-heating. It's important to note that even reheating can sometimes lead to food poisoning. The result is a reduction of the so-called product water activity a w , a measure of unbound, free water molecules in the food that is necessary for microbial survival and growth. The a w of most fresh foods is 0. Yeasts and molds, on the other hand, usually require even lower a w to prevent growth.
Salt and sugar's other antimicrobial mechanisms include interference with a microbe's enzyme activity and weakening the molecular structure of its DNA. Sugar may also provide an indirect form of preservation by serving to accelerate accumulation of antimicrobial compounds from the growth of certain other organisms. Examples include the conversion of sugar to ethanol in wine by fermentative yeasts or the conversion of sugar to organic acids in sauerkraut by lactic acid bacteria.
Microorganisms differ widely in their ability to resist salt- or sugar-induced reductions of a w. Most disease-causing bacteria do not grow below 0. Yet other microorganisms grow quite well under even more highly osmotic, low a w conditions.
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