Historically, the main reason for the addition of salt to food was for preservation. Because of the emergence of refrigeration and other methods of food preservation, the need for salt as a preservative has decreased, but sodium levels, especially in processed foods, remain high. The expected tastes and flavors associated to salt use is enormous coupled with the relative low cost of enhancing the palatability of processed foods, thus making it a key rationale for salt use in food preservation.
However, taste is not the only reason for the continued use of high levels of salt in foods. For some foods, sodium still plays a role in reducing the growth of pathogens and organisms that spoil products and reduce their shelf life. In other applications, sodium levels remain high because salt plays additional functional roles, such as improving texture. A number of other sodium-containing compounds are also used for increasing the safety and shelf life of foods or creating physical properties.
This work begins with a review of the non-taste or flavor-related roles of salt and other sodium-containing compounds in food. The second part will briefly discuss the role that sodium plays in various food categories and provides examples of the sodium content of various foods.

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FOOD SAFETY AND PRESERVATION
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As mentioned previously, the first major addition of salt to food was for taste and to prevent spoilage. Prior to refrigeration and even now, salt was one of the best methods for inhibiting the growth and survival of undesirable microorganisms. Although modern-day advances in food storage and packaging techniques and the speed of transportation have largely diminished this role, salt does remain in widespread use for preventing rapid spoilage (and thus extending product shelf life), creating an inhospitable environment for pathogens, and promoting the growth of desirable micro-organisms in various fermented foods and other products.
Salt’s Role in the Prevention of Microbial Growth
Salt is effective as a preservative because it reduces the water activity of foods. The water activity of a food is the amount of unbound water available for microbial growth and chemical reactions. Salt’s ability to decrease water activity is thought to be due to the ability of sodium and chloride ions to associate with water molecules.
Adding salt to foods can also cause microbial cells to undergo osmotic shock, resulting in the loss of water from the cell and thereby causing cell death or retarded growth. It has also been suggested that for some microorganisms, salt may limit oxygen solubility, interfere with cellular enzymes, or force cells to expend energy to exclude sodium ions from the cell, all of which can reduce the rate of growth.

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PHYSICAL PROPERTIES OF FOOD
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Salt can play a role in the development of physical properties of foods that are beneficial for processing or developing final product qualities. For example, salt levels play an important role in controlling the stickiness of some doughs, easing the processing of some baked goods. In meats, cheeses, and extruded snack products (e.g., cheese balls, shaped potato snacks), salt can help develop the characteristic texture expected by consumers. For example, in cheeses, salt acts to remove excess water, creating a firmer texture and, in some cases, a rind. Salt also contributes to characteristics such as meltability, shredding, stretching, and flow.
Other reasons for the use of salt as a processing technique is to improve the tenderness (which consumers may perceive as juiciness) of leaner cuts of meat. Such cuts of meat can become tough due to their low fat content, which, in the case of beef and pork, is a result of genetic advances made to produce leaner animals. Increasing product yield may be another driver for the use of this technique. Clearly, salt increases the sodium content of the overall product. For example, a regular serving of meat (114 g, reference amount commonly consumed) without enhancement contains 68 mg of sodium, but that same serving of meat injected up to 10 percent of its weight with brine containing 4.5 percent sodium tripolyphosphate and 3.6 percent salt results in 384 mg sodium per serving.
Ready-to-Eat Cereals
Salt is frequently added to breakfast cereals to improve flavor and texture. A survey of children’s cereals from around the world found that, on average, these products are about 1 percent salt by weight. When products are reformulated to reduce sugar content, the addition of salt may be particularly relied upon to maintain the taste of the product.
Rice and Pasta
Salt is often added for flavor during preparation. Many flavored rice and pasta products contain salt in the seasoning, with salt sometimes being used as a bulk carrier to evenly distribute flavorings used in smaller quantities.
Baked Goods
Salt plays multiple roles in breads and other baked goods. Salt, sodium bicarbonate, and sodium salts of leavening acids are mainly spread in baked goods, accounting for 95 percent of the sodium in these products. In most baked goods, salt is used to improve product taste and flavor. Without salt, many baked goods have an insipid taste.
Salt is also responsible for fermentation control and texture in yeast-raised breads. In the mass production of bread, salt levels are used as a tool to control yeast activity. Salt reduces yeast activity by reducing water activity and damaging the membrane of the yeast cells. Salt can also interact with gluten, one of the major proteins in flour responsible for the texture of baked goods, to ease the handling of dough during processing. The result of this interaction reduces the stickiness of the dough.
Salt also helps to control the growth of molds and the Bacillus species of bacteria, thus extending the shelf life of baked goods. The Bacillus species is capable of forming rope-like structures, off-flavors, and discoloration, especially in baked goods high in sugar or fats.

Fresh Meats
Unprocessed cuts of meat have some naturally occurring sodium, but are generally considered low in sodium. However, as described earlier, in recent years, fresh meat products increasingly have been injected with salt- and phosphate-containing brines, increasing the sodium content of fresh products.
Processed Meats
Once meat is further processed into sausages or deli meats, the sodium content increases substantially. Salt is used in meats not only for the flavor it imparts, but also for its role as a preservative and its impact on the textural qualities of the final product. Similar to fresh meats, salt addition to processed meats can help increase water binding in the muscle tissues, leading to increased yields (more product to sell) and greater tenderness. The mechanism by which salt increases water binding is not fully understood, but it is thought to be related to the ability of salt to create repulsion between myofibrillar proteins. At times, phosphate salts containing sodium are also used to improve water binding of muscle foods and to lengthen the time before products turn rancid.
Salt is also used in the processing of products such as sausages and restructured meats. The presence of salt can solubilize myofibrillar proteins that are insoluble in water alone.
Kosher Meats
Salting also plays a role in the kosher processing for meats. All blood must be removed from the tissues for a meat or poultry product to be considered kosher. To achieve this, meat is soaked and then salted. While the salt is used only on the surface of the meat, some is still able to penetrate, leading to increased salt content.
Milk
Cow’s milk—as a source of essential nutrients for a growing mammal—naturally contains some salt. Whole, low-fat, and skim milk all contain similar levels of sodium.
Cheese
Salt in cheese is due to sodium naturally present in milk as well as added salt. While the characteristic salt taste of cheese is popular with consumers, salt also plays roles in the cheese making process that contribute to the texture, shelf life, and safety of the end product.
Butter
Salt was initially added to butter as a preservative prior to widespread use of refrigeration. Salt still plays a preservation role today, but it is less important because access to refrigeration is possible throughout the supply chain. Instead, taste and flavor development are the main drivers for common levels of salt in butter and margarine.
Other Dairy Products
Other dairy products, such as yogurt, ice cream, and puddings, contain salt naturally, from low levels of sodium-containing additives, such as sodium alginate and carrageenan (both thickening agents) or from added flavorings.
Sauces, Gravies, Stocks, Salad Dressings, and Condiments
Sauces, gravies, stocks, salad dressings, and condiments are often high in salt. Reasons for sodium use include flavor, preservation, and improving the stability of emulsions (by improving the solubility of emulsifiers). Flavour is a main reason for adding salt to these products, and saltiness is often one of the major characteristics of these items.
Fruits, Vegetables, Beans, and Legumes
Fresh fruits and vegetables are generally very low in sodium, although salt may be added to fresh produce during home or foodservice preparation. Canned vegetables are typically much higher in sodium than their fresh counterparts. In canning, a liquid medium is important for heat transfer during processing, and a salt brine is generally used because salt enhances the consistency and flavor of vegetables.

In chilled foods, salt can play a role in preventing the growth of pathogens. Vacuum and modified-atmosphere packaging can create oxygen-free environments that favor the growth of Clostridium botulinum. Salt, in addition to other hurdles, can help prevent the growth of this organism. If oxygen is present, Listeria monocytogenes is often a concern because it can grow even at low temperatures. Salt addition can serve as one hurdle to the viability of this organism.
Savory Snacks
Most savory snacks, including chips, nuts, pretzels, popcorn, French fries, and extruded snacks (cheese balls, shaped potato snacks, etc.), have added sodium in the form of salt. The function of salt in these foods is to contribute to taste and overall flavor. For many flavored snack products, salt is used to distribute minor ingredients, such as flavors and colors. Mixing minor ingredients with salt before application can help to ensure even distribution of these components over the surface of the snack.
Confections
Hard candies are generally low in salt, and other confections may have low levels of sodium-containing leavening or texture-modifying agents. Dairy-based confections will contribute to sodium intake due to the sodium naturally present in milk. Chocolates may also contain small amounts of sodium to contribute to flavor and texture. Some confections are likely to contain added salt for flavoring purposes, particularly those with fillings, such as crèmes or jams. Other confections that may include salt for flavoring purposes are caramels, taffy, and nut-containing candy.
Beverages
Salt is often present in sports drinks for the stated purpose of rehydrating the body during or after physical activity, although the medical justification for the sodium contained in these drinks under the conditions consumed (e.g., high school sports activities) is not clearly demonstrated.

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