Using Salt as a Food Preservative

Salt has been used as a food safety aid since ancient times. While salt helps preserve food by reducing water content and disrupting microbial cells, it takes very high salt concentrations (around 10% or more) to prevent bacterial growth—much higher than what is found in most foods you eat.

Beef jerky, pickles, and smoked salmon are just a few examples of foods that are preserved using salt. While it can keep them fresher longer, it doesn't entirely rule out the possibility they can give you food poisoning.

This article goes over how salt is used to keep food fresh, including the types of foods that are commonly preserved this way.

How Salt Preserves Food

As a preservative, salt works in two ways:

1) Salt Dries Food Out

Salt draws water out of food and dehydrates it. All living things need water and cannot grow without it—including bacteria that can cause food poisoning.

For example, in butter, salt draws water out and leaves fat behind, which helps butter from spoiling.

2) Salt Kills Microbes

High salt is toxic to most—but not all—microbes because of the effect of water pressure.

Water goes between cells in the environment to make the concentration of salt (and other solutes) the same on both sides of the cell. In very high salt solutions, many microbes will explode because of the difference in pressure between the outside and inside of the organism.

High salt can also be toxic to processes inside microbes, like DNA and enzymes. Solutions that are high in sugar have the same effects on microbes, which is why it is used as a preservative in foods like jams and jellies.

Misconceptions About Salt As Preservative

If you assume that salty foods aren't a food poisoning risk, think again.

While it's true that many of the bacteria that can cause food poisoning do not grow well in salty conditions, there are some that need salt to grow.

Called halophiles, they don't exactly love salt, but they can survive in it because they have a warning system for detecting very salty conditions that helps them avoid losing water (halotolerant).

It's also important to know that bacteria are not the only thing that can make you sick. Molds can also be a source of foodborne illness and are able survive higher salt levels than bacteria.

Salt Content of Foods: Is It High Enough to Be Safe?

None of the foods that may immediately come to mind when thinking of something salty come even close to the 10% salt threshold for preventing bacterial growth. Even foods traditionally thought of as salt-preserved foods don't.

The percentage of salt is calculated by dividing the total weight of the food by the weight of the salt. The following nutrition information was obtained by using CalorieKing's food database.

Salt-Preserved Foods

• 1 dill pickle: 306 mg/34 g = 0.9% salt
• 1 piece beef jerky: 443 mg/20 g = 2.2% salt
• 1 slice ham: 365 mg/9.3 g = 3.9% salt

Additional features these foods have—such as dehydration (beef jerky) or the addition of acid (pickles) or preservatives (ham)—help prevent spoilage. In addition, many salt-preserved foods need to be refrigerated after opening to slow microbial growth.

Other Salty Foods

• 1 serving Nacho Cheese Doritos: 314 mg/48 g = 0.7% salt
• 1 serving Campbell’s Chicken Noodle Soup (condensed): 1,779 mg/252 g = 0.7% salt
• 1 serving McDonald’s French fries (medium): 260 mg/117 g = 0.2% salt
  

Brines and Condiments

Brines and condiments are known to have high salt content, but not high enough to inhibit bacterial growth. For example:

• 1 packet ketchup: 100 mg/8.5 g = 1.1% salt
• 1 packet mustard: 65 mg/5.67 g = 1.1% salt
• 1 packet soy sauce: 333 mg/5.67 g = 5.8% salt

Do Higher Salt Levels Prevent Spoilage Better Than Lower Salt Levels?

For most edible foods, the answer is no. And adding lots of salt to foods in an attempt to keep them fresh can put you at risk of sodium poisoning.

Bacteria grow best in conditions saltier than most foods we eat. Science labs where bacteria are routinely grown for experiments use a solution called Luria Broth or Lysogeny Broth (LB).

The solutions come in different formulas and salt concentrations depending on what the organisms need to grow. Some LBs have salt concentrations of around 10% while others are between 0.5%-5%.

Many of them also have sugar and other ingredients like yeast that help bacteria grow.

How to Keep Your Food Safe

The Centers for Disease Control and Prevention (CDC) estimates that, annually, 48 million people (1 in 6) get infected by a foodborne illness, 128,000 are hospitalized as a result of one, and 3,000 die.

There is plenty of evidence that salty foods are not microbe-proof. While salt may not be the solution, there are plenty of steps you can take to keep your food safe.

• Practice good kitchen safety. For example, never use the same cutting board for raw meat and produce (e.g., vegetables, fruit).
• Buy foods well before the expiration dates. Even if a food is not expired, if the smell, appearance, or texture seems off, throw it out.
• Stay up to date on the news to learn about any food-poisoning outbreaks or recalls.
• Avoid unpasteurized milk to reduce your risk of milk-borne infections like listeria.
• Refrigerate foods promptly after eating and use safe food-storage practices.
• Heat foods thoroughly when reheating. However, it's important to note that even reheating can sometimes lead to food poisoning. Some bacteria, such as Staph, make toxins that are heat stable and won't be killed by reheating food.
• Know the signs and symptoms of food poisoning. Talk to your healthcare provider if you think you may have a foodborne illness.

Summary

Salt can be an effective way to preserve food but also increases the sodium content of the food. Using too much salt to try to keep food fresh can also have the opposite effect if it creates the right conditions for bacteria to grow.

Even without salt, there are plenty of steps you can do to keep your food safe, including practicing proper food safety.