Why does salt preserve food?

In this brief guide, we are going to answer the question “why does salt preserve food” with an in-depth analysis of the characteristics that makes salt a good preservative. Moreover, we are going to discuss the salt concentration that is required to preserve the food.

So without much ado, let’s dive in and figure out more about it.

Why does salt preserve food?

Salt preserves food owing to its two main characteristics. It dries the food and kills the microbes thereby increasing the shelf life of food.

Dries the food

Salt has the property to draw water out of the food and resultantly make it dry. Owing to this property of salt, it is used as a preservative to store and preserve different food items including meat, vegetables, etc.

In the case of meat, what we do is, apply salt in a generous amount on the meat and leave it. After some time the salt draws out the water from the meat, thereby making it dry.

So what happens during this process is that after applying salt on the meat, the outside of the meat becomes hypertonic and has a higher concentration of salt present at outside as compared to inside the cells of the meat. Therefore the water tends to move from the point of lower solute concentration (cells of meat) to the point of higher solute concentration (outside the meat). Thus salt draws out water from different food items.

The same is the process for the vegetables in which the addition of salt makes the surrounding hypertonic that resultantly draws the water out of the vegetables and thereby makes them saggy and too much softened.

As we all know that bacteria and microbes need moisture and a particular temperature to grow on the meat. So the meat that is devoid of its moisture won’t provide a suitable environment for the microbes to grow onto. Therefore the bacterial growth will be halted and the meat that has been cured lasts for a very long time.

Most of the fresh foods have a water activity of 0.99, and lowering it to 0.91 can considerably protect the foods from most of the bacteria and salt does that for you.

Kills the bacteria

Salt is very toxic and harmful for some microbes and bacteria. In a hypertonic solution owing to the process of osmosis and plasmolysis, the water will move out of the bacterial cells, thereby shrinking and killing them. 

Moreover salt can also be harmful to the internal machinery like the DNA of the bacteria, therefore salt has the ability to kill the bacteria, thereby protecting the food from the bacteria and preserving it for a long time.

Moreover salt also helps in the process of fermentation that considerably increases the shelf life of foods. You can read more about the role of salt in fermentation here.

What is osmosis?

Osmosis is the process in which the solvent moves from a point of lower solute concentration to a point of higher solute concentration. The process of osmosis maintains the solute-solvent balance throughout the semi-permeable membranes and this process also plays an important role in the body of living organisms.

What is plasmolysis?

Plasmolysis is a process that takes place because of osmosis. In plasmolysis, the cell loses its water content when it is placed in a hypertonic solution (the solution having a high solute concentration). As the cell loses its water content, it shrinks.

What should be the salt concentration to preserve food?

So there is a concept, that you need to use a 10% salt solution in order to preserve the food and protect it against both the pathogenic and spoilage bacteria, circling preservation of food using salt.

So when it comes to microbes and their salt-bearing potentials, apart from halophiles (salt-loving bacteria), all other bacteria can not survive a salt concentration of more than 10%.

How will a 10% salt solution taste like?

So in order to get a 10% salt solution you need to dissolve 10 g of salt in 100 ml of water which means that in order to get a cup of 10% salt solution you should add 24 g of salt in 240 ml of water. 

To estimate the saltiness of this solution just know that seawater is only a 3.5% salt solution, so what you are targeting is a solution that is 3 times saltier than seawater. 

Do higher salt levels prevent spoilage better than lower-level salts?

For most of the foods, the answer to this question is “No”, as the higher salt levels (more than 4%) do not have any noticeable additional benefit on the prevention of food spoilage. Most of the traditional foods like pickles (0.97%), a slice of ham (3.9%) that are considered to have long shelf life have their salt concentration less than 4%. The commercially processed brines and condiments do have a higher concentration of salt like soy sauce has 5.8% salt concentration.

Moreover, you should keep in mind that consuming a food that has a high salt concentration will put you at the risk of sodium poisoning. Moreover, it can also result in causing high blood pressure and related health problems. 

Conclusion

In this brief guide, we answered the question “why does salt preserve food” with an in-depth analysis of the characteristics that makes salt a good preservative. Moreover, we discussed the salt concentration that is required to preserve the food.

Citations

https://www.verywellhealth.com/eat-it-with-a-grain-of-salt-1958878

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Mahnoor Asghar is a Clinical Nutritionist with a bachelor's degree in Nutrition and Dietetics. She is compassionate and dedicated to playing her part in the well-being of the masses. She wants to play a fruitful role in creating nutrition and health-related awareness among the general public. Additionally, she has a keen eye for detail and loves to create content related to food, nutrition, health, and wellness.

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