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4
Preservation and Physical Property Roles of Sodium in Foods

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 (He and MacGregor, 2007), but sodium levels, especially in processed foods, remain high. As discussed in Chapter 3, the tastes and flavors associated with historical salt use have come to be expected, and the relatively low cost of enhancing the palatability of processed foods has become a key rationale for the use of salt in food (Van der Veer, 1985). However, taste is not the only reason for the continued use of high levels of sodium 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 chapter begins with a review of the non-taste or flavor-related roles of salt and other sodium-containing compounds in food. The second part of the chapter briefly discusses the role that sodium plays in various food categories and provides examples of the sodium content of various foods.

FOOD SAFETY AND PRESERVATION

As mentioned previously, the first major addition of sodium to foods was as salt, which acted to prevent spoilage. Prior to refrigeration, salt was



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4 Preservation and Physical Property Roles of Sodium in Foods H istorically, 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 (He and MacGregor, 2007), but sodium levels, especially in processed foods, remain high. As discussed in Chapter 3, the tastes and flavors associated with historical salt use have come to be expected, and the relatively low cost of enhancing the palatability of processed foods has become a key rationale for the use of salt in food (Van der Veer, 1985). However, taste is not the only reason for the continued use of high levels of sodium 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 chapter begins with a review of the non-taste or flavor-related roles of salt and other sodium-containing compounds in food. The second part of the chapter briefly discusses the role that sodium plays in various food categories and provides examples of the sodium content of various foods. FOOD SAFETY AND PRESERVATION As mentioned previously, the first major addition of sodium to foods was as salt, which acted to prevent spoilage. Prior to refrigeration, salt was 

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 STRATEGIES TO REDUCE SODIUM INTAKE one of the best methods for inhibiting the growth and survival of undesir- able microorganisms. Although modern-day advances in food storage and packaging techniques and the speed of transportation have largely dimin- ished 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. Other sodium- containing compounds with preservative effects are also used in the food supply. 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 (Fennema, 1996; Potter and Hotchkiss, 1995). 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 (Davidson, 2001). 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 (Shelef and Seiter, 2005). Today, few foods are preserved solely by the addition of salt. However, salt remains a commonly used component for creating an environment re- sistant to spoilage and inhospitable for the survival of pathogenic organisms in foods. Products in the modern food supply are often preserved by mul- tiple hurdles that control microbial growth (Leistner, 2000), increase food safety, and extend product shelf life. Salt, high- or low-temperature process- ing and storage, pH, redox potential, and other additives are examples of hurdles that can be used for preservation. As shown in Figure 4-1, no single preservation method alone would create a stable product; when combined, however, these methods result in a desirable, stable, and safe product. For example, a food might be protected by a combination of salt, refrigeration, pH, and a chemical preservative. Multiple-hurdle methods offer the additional benefit of improving other qualities of some foods. For example, hurdle methods can be used to reduce the severity of processing needed, allow for environmentally friendly packaging, improve the nutritional quality of foods (by achieving microbio- logical safety with less salt, sugar, etc.), and reduce the use of preservatives that are undesirable to some consumers (Leistner and Gould, 2005).

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 ROLES OF SODIUM IN FOODS FIGURE 4-1 Examples of the multiple-hurdle method for reducing microbial ac- tivity in foods. At the level employed in many foods, individual hurdles may not provide adequate protection from spoilage or pathogenic microorganisms. When multiple hurdles are combined, each hurdle plays a role in reducing microbial ac- tivity (displayed as →) until, eventually, 4-1microbial population is so weakened Figure the revised Bitmapped that it cannot cross any further hurdles and the food is protected from spoilage and pathogen survival (letters a, b, and c). If hurdles are insufficient to reduce microbial growth, food products may not be adequately protected (letter d). NOTE: aw = water activity; Eh = redox potential; F = heating; pH = acidity; pres = preservatives; t = chilling. SOURCE: Reprinted from Trends in Food Science and Technology, 6(2), Leistner and Gorris, Food preservation by hurdle technology, 41–46, Copyright © 1995, with permission from Elsevier. Salt’s Role in Fermentation to Preserve Foods Salt commonly plays a central role in the fermentation of foods. Fer- mentation is a common process for preserving foods, in which fresh foods are transformed to desirable foods that can be preserved for longer periods of time than their fresh counterparts due to the actions of particular types of microbes (Potter and Hotchkiss, 1995). Products such as pickles, sauer- kraut, cheeses, and fermented sausages owe many of their characteristics

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 STRATEGIES TO REDUCE SODIUM INTAKE to the action of lactic acid bacteria. Salt favors the growth of these more salt-tolerant, beneficial organisms while inhibiting the growth of undesir- able spoilage bacteria and fungi naturally present in these foods (Doyle et al., 2001). Salt also helps to draw water and sugars out of plant tissues during fermentation of vegetables. This water aids fermentation by filling any air pockets present in fermentation vats, resulting in reduced oxygen conditions that favor growth of lactic acid bacteria. The release of water and sugars also promotes fermentation reactions in the resulting brine, increasing the rate of the fermentation process (Doyle et al., 2001; Potter and Hotchkiss, 1995). Role of Other Sodium Compounds A number of other sodium-containing compounds provide preservative effects in foods. There is a wide variety of these preservatives with various product uses. Preservatives can act to reduce microbial activity and also may, like salt, act as a hurdle to microbial growth and survival. Some ad- ditives may also play a role in preserving food quality by reducing undesir- able chemical reactions, such as lipid oxidation and enzymatic browning. In some cases, the compounds can have more than one function in a food product, with preservative effects being one of several reasons for use. A brief listing of common sodium-containing compounds used for food preservation and the foods with which they are associated can be found in Table 4-1. TABLE 4-1 Common Sodium-Containing Compounds Used for Food Preservation Compound Name Food to Which the Compound Is Added Disodium ethylenediaminetetraacetic acid Salad dressing, mayonnaise, canned seafood, (EDTA) fruit fillings Sodium acetate Baked goods, seafood Sodium ascorbate Meat products Sodium benzoate Beverages, fermented vegetables, jams, fruit fillings, salad dressings Sodium dehydroacetate Squash Sodium diacetate Condiments Sodium erythorbate Meat, soft drinks Sodium lactate Meat products Sodium nitrate Cured meats Sodium nitrite Cured meats Sodium phosphates Meat products, cheese, puddings or custards Sodium propionate Cheese, baked goods Sodium sulfite Fruit and vegetable products, seafood SOURCE: Doyle et al., 2001.

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 ROLES OF SODIUM IN FOODS Challenges and Innovations for Lowering Sodium While Maintaining Safety and Shelf Life For many foods, reducing the sodium content of the product should not create food safety or spoilage concerns. Such foods include frozen products, products that are sufficiently thermally processed to kill pathogenic organ- isms (e.g., canned foods), acidic foods (pH < 3.8), and foods in which water activity remains low when sodium is removed (e.g., foods with low water activity due to high sugar content) (Reddy and Marth, 1991; Stringer and Pin, 2005). For other foods, reducing sodium content has the potential to increase food spoilage rates and the presence of pathogens. For these foods, product reformulation, changes in processing, and changes in handling may be required to ensure that the product has an adequate shelf life and to prevent pathogen growth. Such efforts do incur additional costs and require careful attention to ensure that new formulations and processes are sufficient to ensure product safety. These issues are discussed further in Chapters 6 and 8. Foods using sodium as a hurdle to retard microbial growth and survival present a reformulation challenge, since changing the sodium content alters the impact (or height) of the water activity hurdle. Changing this single hurdle may impact the safety and quality of the food because other hurdles that are present (pH, temperature, etc.) may work only in combination with the original sodium level. To maintain a safe, good-quality product, reformulation may have to include the introduction of additional hurdles or an increase in the impact of existing hurdles. If such additional measures are not taken during sodium reduction efforts, the remaining products may not be stable. For example, in cured meats, reducing the sodium content (by removing both salt and sodium nitrite) could allow for rapid growth of lactic acid bacteria and action by proteolytic microorganisms, resulting in a product that spoils more rapidly (Roberts and McClure, 1990; Stringer and Pin, 2005). In some foods, pathogen growth, rather than spoilage, may become a concern. There is speculation that some past salt reduction efforts may not have adequately accounted for the need to adjust additional hurdles to microbial growth. In the United Kingdom, salt reduction efforts in chilled, ready-to- eat foods were cited as one factor that may have contributed to an increase in the incidence of listeriosis from 2001 to 2005 (Advisory Committee on the Microbiological Safety of Food, 2008). Listeriosis is caused by Listeria monocytogenes, which has a high thermal stability and is able to grow and survive at refrigeration temperatures and elevated salt levels (Zaika and Fanelli, 2003). To decrease the risk of listeriosis, a draft report of the United Kingdom’s Advisory Committee on the Microbiological Safety of Food called on the Food Standards Agency to work closely with food

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 STRATEGIES TO REDUCE SODIUM INTAKE manufacturers to ensure that the microbial safety of food products would not decrease with changes in formulation to reduce salt (Advisory Commit- tee on the Microbiological Safety of Food, 2008). There is also evidence suggesting that reductions in salt might result in greater risk of toxin formation by Clostridium botulinum (the organism responsible for botulism) in certain foods if additional hurdles are not in- corporated. This is particularly the case for foods that have not been heated sufficiently to inactivate C. botulinum spores and have little oxygen present. Processed cheese (Glass and Doyle, 2005; Karahadian et al., 1985), meat products (Barbut et al., 1986), and sous vide products (products that are prepared in vacuum-sealed plastic pouches and heated at low temperatures for long times1) have been recognized as having potential for C. botulinum control problems when sodium is reduced (Simpson et al., 1995). For ex- ample, decreases in salt content from 1.5 to 1.0 percent by weight greatly reduced the time needed for C. botulinum type A and B spores to produce toxins in sous vide spaghetti and meat sauce products when stored at typical refrigeration temperatures. At salt concentrations at or above 1.5 percent, no toxin production was detected from the inoculated products during the 42-day storage period, while at 1.0 percent salt addition, toxins were produced within 21 days (Simpson et al., 1995). Similarly, turkey frankfurters inoculated with C. botulinum and held at 27°C showed more rapid toxin production when salt content was 2.5 percent than when it was 4.0 percent (Barbut et al., 1986). In addition to C. botulinum and L. monocytogenes, the growth of other foodborne pathogens may be more rapid in foods with reduced contents of salt and other sodium-containing preservatives. These pathogens include Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, Aeromonas hydrophila, Clostridium perfringens, and Arcobacter (D’Sa and Harrison, 2005; Reddy and Marth, 1991; Stringer and Pin, 2005). While the pathogens described above must be taken into account, product developers and researchers have been able to accomplish sodium reductions even in products such as processed cheese and processed meats (Reddy and Marth, 1991). A number of hurdles can be added or increased when sodium is reduced to ensure that a product’s safety is maintained. Examples of additional hurdles are listed in Table 4-2. This list includes a number of emerging technologies (e.g., high-pressure processing, electron beam irradiation) that may have wider applications in the future. Compounds, such as potassium chloride (Barbut et al., 1986) and mixtures of potassium lactate and sodium diacetate (Devlieghere et al., 2009), that might be used to replace salt and other sodium-containing pre- 1 Available online: http://amath.colorado.edu/~baldwind/sous-vide.html (accessed October 25, 2009).

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 ROLES OF SODIUM IN FOODS TABLE 4-2 Hurdles That Could Be Added to Counteract Microbial Activity in Sodium-Reduced Foods Chemical Physical Biological Organic acids Additional heating Bacteriocins (e.g., nisin) Nitrites Cooler storage Protective cultures Phosphates Drying Fatty acid esters Irradiation (e.g., electron Ingredients with natural beam) antimicrobial properties Hydrostatic pressure (e.g., spice extracts, processing smoke) Controlled-atmosphere Potassium chloride storage or packaging SOURCES: Barbut et al., 1986; Doyle et al., 2001; Rybka-Rodgers, 2001. servatives have been shown to be somewhat effective at retarding growth and toxin production by pathogens. The effectiveness of alternative salts relative to sodium chloride seems to vary based on the pathogen of interest (Barbut et al., 1986). Partially replacing salt with other compounds, such as potassium chlo- ride and calcium chloride, may also be possible in fermented products (Bautista-Gallego et al., 2008; Reddy and Marth, 1991; Yumani et al., 1999). However, these alternatives may be less effective than salt so higher concentrations may be needed in formulations to achieve the same func- tionality (Bautista-Gallego et al., 2008). Some predictive models have been developed that may be promising methods of screening new product formulations for their potential to grow pathogenic microorganisms. A large study conducted by Kraft foods (Legan et al., 2004) modeled the impact of salt on the growth of L. monocytogenes and used this modeling technique to establish no-growth formulations of cured meat products that contain lactate and diacetate to prevent growth of L. monocytogenes. PHYSICAL PROPERTIES OF FOOD 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 (Hutton, 2002; Vetter, 1981). In meats, cheeses, and extruded snack products (e.g., cheese balls, shaped potato snacks), salt can help develop the characteristic texture expected by consumers (Desmond, 2007; Guinee and Fox, 2004; Guinee and O’Kennedy, 2007; Hedrick et al., 1994). For example, in cheeses, salt

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 STRATEGIES TO REDUCE SODIUM INTAKE acts to remove excess water, creating a firmer texture and, in some cases, a rind (Guinee and Fox, 2004). Salt also contributes to characteristics such as meltability, shredding, stretching, and flow (Reddy and Marth, 1991). Other sodium-containing compounds are also used to establish physical properties of food products. Some of the more common sodium-containing compounds are used in baked goods (e.g., sodium bicarbonate, also known as baking soda) for leavening and to condition dough for easier processing. For a variety of products, such as sauces and dressings, emulsification and thickening agents may contain sodium. Examples of sodium-containing compounds that impact the physical properties of foods, along with their functions, are provided in Box 4-1. The practice of enhancing raw poultry, beef, pork (Baublits et al., 2006; Brashear et al., 2002), and seafood products (Rattanasatheirn et al., 2008; Thorarinsdottir et al., 2004) with solutions that contain sodium is also worth noting. Typically, these enhancement solutions include salt and sodium phosphates. One reason for the use of this 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 (Detienne and Wicker, 1999). Increasing product yield may be another driver for the use of this technique (Detienne and Wicker, 1999). Clearly, salt and sodium phosphates increase the sodium content of the overall product. For example, a regular serving of meat (114 g, reference amount commonly consumed) without enhance- ment 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 (DeWitt, 2007). Challenges and Innovations for Lowering Sodium While Maintaining Physical Properties The difficulty of reducing sodium without losing desirable physical properties is dependent on the specific food application and the availability of other ingredients that can fulfill similar functions. In some foods (e.g., certain cheeses and processed meats), the salt used to create special physi- cal properties may be impossible to remove, given current technologies. As previously mentioned in the discussion of challenges to reduce sodium while maintaining food safety, reformulation has a number of costs that are described further in Chapter 6. Still, for many products, more salt may be added than is truly needed for the desired physical property. In these cases, research to determine criti- cal salt levels may be necessary to quantify the amount of salt that can be

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 ROLES OF SODIUM IN FOODS BOX 4-1 Common Sodium-Containing Compounds and Their Functions in Food Emulsifying Agents: Stabilizing Agents: Sodium pyrophosphate Disodium Dioctyl sodium sulfosuccinate ethylenediaminetetraacetic Disodium hydrogen phosphate acid (EDTA) Sodium alginate Disodium pyrophosphate Sodium caseinate Potassium sodium L-tartrate Sodium phosphate Sodium alginate Trisodium citrate Sodium carboxymethylcellulose Trisodium phosphate Sodium caseinate Sodium stearoyl lactylate Trisodium citrate Sodium stearoyl lactylate Buffering Agents: Neutralizing Agents: Aluminum sodium sulfate Disodium hydrogen phosphate Trisodium phosphate Sodium adipate Sodium sesquicarbonate Sodium dihydrogen citrate Sodium phosphate Sodium dihydrogen phosphate Sodium DL-malate Sodium DL-malate Sodium dihydrogen phosphate Sodium hydrogen carbonate Sodium dihydrogen citrate Sodium phosphate Sodium citrate Trisodium citrate Sodium adipate Trisodium phosphate Aluminum sodium sulfate Sodium potassium tartrate Anticaking Agents: Sodium acetate Sodium aluminosilicate Thickening Agents: Sodium ferrocyanide Sodium alginate Flavor-Enhancing Agents: Sodium carboxymethylcellulose Monosodium glutamate Disodium 5′-guanylate Moisture-Retaining Agents: Disodium 5′-inosinate Sodium hydrogen DL-malate Disodium 5′-ribonucleotides Sodium lactate Sodium lauryl sulfate Leavening Agents: Texture-Modifying Agents: Sodium bicarbonate Disodium pyrophosphate Sorbitol sodium Sodium acid pyrophosphate Sodium tripolyphosphate Sodium aluminum phosphate Pentasodium triphosphate Sodium hydrogen carbonate Disodium hydrogen phosphate Dough-Conditioning Agents: Bleaching Agent: Sodium stearoyl lactylate Sodium metabisulfite Sodium stearyl fumarate SOURCE: Lewis, 1989.

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00 STRATEGIES TO REDUCE SODIUM INTAKE removed. For example, attempts to reduce sodium in natural and processed cheese products while maintaining desirable textures and achieving a safe product have been successful using new technologies, such as ultrafiltration (Reddy and Marth, 1991; Van der Veer, 1985). Similarly, in enhanced meat, some brine injection may be desirable to increase the palatability of leaner cuts of meat (Detienne and Wicker, 1999) and help consumers avoid fattier meats that are naturally more tender. However, it is likely that, for many of these products, additional brine is added to further reduce moisture loss (or purge) that normally occurs in the product during its retail shelf life. The benefit that may result from additional brine at that point may be more for economic than sensory reasons, and the brine may not be needed to create acceptable products. In other products, additional salt may be added for enhanced taste and flavor. Table 4-3 shows the difference in sodium content of similar foods in TABLE 4-3 Differences in Sodium Content of Similar Foods Sodium Serving Sodium (mg/100 g Food Size (g) (mg) product) Hams Carl Buddig Honey Ham 56 460 821 Oscar Mayer Baked Cooked 63 760 1,206 Oscar Mayer Shaved Smoked 51 640 1,255 Pork Sausage, Sage 365 Brown & Serve Links 56 380 679 Jimmy Dean Premium 56 420 750 Bob Evans Savory 56 570 1,018 Turkey, Fresh or Frozen Butterball Fresh Whole Turkey Breast 112 55 49 Shadybrook Farms Turkey Breast Cutlets 112 240 214 Marval Prime Young Turkey Breast (frozen) 112 390 348 Butterball Frozen Fully Cooked Whole Turkey Breast 84 500 595 Cheese, Cheddar, Sliced Kraft Cracker Barrel Natural Sharp Slices 28 180 643 Great Value (Wal-Mart) Mild 19 135 711 Kraft Deli Deluxe Sharp Slices 28 440 1,571 Buns, Hot Dog Pepperidge Farm 50 190 380 Wonder 8 43 210 488 Great Value (Wal-Mart) Enriched 43 230 535 NOTE: g = gram; mg = milligram. SOURCE: CSPI, 2008. “Salt Assault: Brand-name Comparisons of Processed Foods.” Re- printed with permission.

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0 ROLES OF SODIUM IN FOODS which sodium plays a role in creating a physical property or in preser- vation. The varied sodium levels suggest that the sodium levels in some products may be greater than those needed for these functions. Cases such as these may provide opportunities to lower the sodium content of some foods. A similar conclusion was reached by researchers who surveyed the sodium content of processed foods in Australia and found variation in the salt concentration of comparable foods, frequently ≥ 50 percent between the highest- and lowest-salt foods within a category (Webster et al., 2010). Another survey2 found differences in the salt content of the same brand name foods, including fast food restaurant items, among different coun- tries. Many branded food manufacturers operate internationally and may participate in sodium reduction programs in other countries. Alternatives that can replace the texture development functions of sodium are limited. However, advances in ingredient technologies have made it possible to replace some salt. Restructured and emulsified items (e.g., sausages, deli meats), for example, are products for which lower-sodium ingredient options have been identified. In these products, functional pro- teins (e.g., soy or milk), hydrocolloids (e.g., gums or alginates), and starches have replaced some of the functionality of the salt-soluble proteins that form a gel network and “glue” the meat pieces together in higher-salt products (Desmond, 2006). In addition, sodium tripolyphosphate, potassium phos- phates, and transglutaminase have been used to improve the stability of reduced-salt emulsified meats in which there may be less salt-soluble protein available to coat and stabilize fat particles (Ruusunen et al., 2002). In their review on sodium reduction, Reddy and Marth (1991) described several studies successfully demonstrating that sodium reduction in meats could result in products evaluated to have acceptable functionality and flavor. In pork, they described a modified processing procedure referred to as emulsion coating that reduced the salt content by 50 percent in chunked and formed ham products. Successful reductions in sodium were also reported for fresh pork sausage, frankfurters, bologna, and comminuted meat batters. Another method of reducing sodium in foods is to find alternatives to other (non-salt) sodium-containing additives. A number of alternatives have been developed. Table 4-4 provides examples (although not an exhaustive list) of alternatives to sodium-containing compounds that are often used for leavening, dough conditioning, and emulsifying. Some industries are conducting their own research or funding universi- ties to research alternative processing methods as another strategy to reduce sodium. For example, these approaches include use of pre-rigor mortis muscle in emulsified and restructured meat products (Desmond, 2006) 2 Availableonline: http://www.worldactiononsalt.com/media/international_products_survey_ 2009.xls (accessed February 22, 2010).

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0 STRATEGIES TO REDUCE SODIUM INTAKE Dairy Foods The sodium content of selected dairy foods is listed in Table 4-8. Milk Cow’s milk—as a source of essential nutrients for a growing mammal— naturally contains some sodium. Whole, low-fat, and skim milk all contain similar levels of sodium. Cheese Sodium 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. A function of salt in most cheese production is to draw water or whey out of cheese curds. Cheese curds are formed during the initial stages of cheese production when casein proteins in milk coagulate. The coagulation process also traps other milk components, such as fat, carbohydrates (lac- tose), minerals, and water. Often, more water is trapped in the curd than is desired in the final product. Commonly, cheese curds will be pressed prior to the ripening process to remove this excess water, but pressing alone is usually insufficient. Addition of salt by brine solution or dry rub is used to remove additional water by osmosis to reach desired moisture levels (Potter and Hotchkiss, 1995; Walstra et al., 1999). TABLE 4-8 Sodium Content of Dairy Foods Average Sodium Average Sodium Dairy Food RACC Average Content (mg/RACC) Content (mg/100 g) 240 mL ≈ 240 g Whole milk 94 39 240 mL ≈ 240 g Skim milk 101 42 Yogurt 225 g 135 60 American cheese 30 g 452 1,505 Cheddar cheese 30 g 190 632 1 T ≈ 14 g Butter 81 576 ½ c ≈ 70 g Vanilla ice cream 52 74 ½ c ≈ 113 g Chocolate pudding 349 309 NOTE: c = cup; g = gram; mg = milligrams; mL = milliliter; RACC = reference amount customarily consumed; T = tablespoon. SOURCES: 21 CFR 101.12; FDA, 2007.

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0 ROLES OF SODIUM IN FOODS Removal of water from cheese curds helps to reduce the water available for microbial growth, reducing the likelihood of microbial spoilage and pathogen growth. For some types of cheese, salting creates a hard rind that protects the cheese during ripening and transport. In addition, the presence of salt in the resulting moisture-reduced cheese decreases the water activ- ity of the product. Lowering water activity controls the growth of cheese starter cultures, which can influence the pH, texture, and ripening of cheese (Guinee and Fox, 2004). Texture is also altered by the removal of excess water and by the overall sodium content of the cheese. Cheeses with lower salt content are typically soft, pasty, and adhesive, while those with higher content are harder, drier, and crumblier (Guinee and Fox, 2004). For example, ricotta and Swiss cheese have a lower sodium content than firmer cheeses, such as cheddar and gouda, which in turn have a lower sodium content than hard cheeses, such as parmesan (Van der Veer, 1985). Salt also impacts physical characteristics, such as meltability, shredding, stretching, and flow (Reddy and Marth, 1991). Texture is also altered by the activity of proteolytic enzymes, and the activity of proteolytic enzymes is altered by salt (Guinee and Fox, 2004). Processed cheeses can have additional sodium in the form of sodium phosphates and sodium citrates, which are emulsifying agents important to the formation and final texture of these products (Guinee and O’Kennedy, 2007). Non-salty tastes are also affected by the presence of salt. Undesirable bitterness in cheese is thought to be related to insufficient salt levels (Guinee and Fox, 2004). In addition, the activity of starter cultures is impacted by salt level and time of addition. Starter cultures are responsible for the production of a number of flavor compounds in addition to acid (Doyle et al., 2001). 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 com- mon levels of salt in butter and margarine (Brady, 2002; Hutton, 2002). Other Dairy Products Other dairy products, such as yogurt, ice cream, and puddings, contain sodium naturally, from low levels of sodium-containing additives, such as sodium alginate and carrageenan (both thickening agents) (Goff, 1995; Lal et al., 2006), or from added flavorings.

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0 STRATEGIES TO REDUCE SODIUM INTAKE Sauces, Gravies, Stocks, Salad Dressings, and Condiments As shown in Table 4-9, sauces, gravies, stocks, salad dressings, and condiments are often high in sodium. Reasons for sodium use include flavor, preservation, and improving the stability of emulsions (by improving the solubility of emulsifiers). Flavor is a main reason for adding salt to these products, and saltiness is often one of the major characteristics of these items (Hutton, 2002). In most condiments, salt also plays a role in preservation (Brady, 2002), combined with other hurdles to microbial growth. Sodium-containing ad- ditives also may be added to salad dressings, sauces, and condiments to act as emulsifiers or preservatives. For soy sauce, which is very high in sodium, salt is needed to influence the fermentation process in its production (Doyle et al., 2001). 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 prepara- tion. Fruits that are processed further typically remain low in sodium (Van der Veer, 1985). Frozen vegetables generally do not have additional sodium unless components such as breadings or sauces are added to the product (Van der Veer, 1985). Dried pulses (beans, lentils, peas) are naturally low in sodium but they are often salted during home and foodservice cooking. 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 (Hutton, 2002; Van der Veer, TABLE 4-9 Sodium Content of Sauces, Gravies, Stocks, Salad Dressings, and Condiments Average Sodium Average Sodium Food Product RACC Content (mg/RACC) Content (mg/100 g) Italian dressing 30 g 443 1,478 Low-calorie buttermilk dressing 30 g 298 994 ¼ c ≈ 60 g Brown gravy 341 568 ¼ c ≈ 60 g White sauce 225 375 1 T ≈ 15 g Mayonnaise 81 543 1 tsp ≈ 5 g Mustard 58 1,156 2 T ≈ 30 g Salsa 184 612 NOTE: c = cup; g = gram; mg = milligram; RACC = reference amount customarily consumed; T = tablespoon; tsp = teaspoon. SOURCES: 21 CFR 101.12; FDA, 2007.

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 ROLES OF SODIUM IN FOODS 1985). However, salt is not essential for the canning process and no-salt- added canned vegetables are marketed. One study (Jones and Mount, 2009) that tested multiple brands of five types of popular canned beans showed that draining the beans for 2 minutes reduced sodium by 36 percent, and the draining treatment plus 10 seconds of rinsing followed by an additional 2 minutes of draining reduced sodium by 41 percent. According to one survey, draining and rinsing of canned beans is a relatively common food preparation technique (Bush Brothers and Company, 2009). Other stud- ies have shown that treatment involving draining, rinsing, and/or soaking of various canned and packaged foods results in sodium reduction (Sinar and Mason, 1975; Vermeulen et al., 1983; Weaver et al., 1984). The so- dium content of selected fruits, vegetables, beans, and legumes is shown in Table 4-10. Pickled vegetables such as sauerkraut and cucumbers are also high in sodium because of the salt added to drive the fermentation process and to maintain a crisp texture (Brady, 2002). Mixed Dishes Combination foods, such as pizza, soups, stews, casseroles, and ready- to-eat meals, are usually high in sodium, as shown in Table 4-11. Sodium in these foods comes from many sources and has multiple functions; when combined into a single serving, the sodium from these varied sources can TABLE 4-10 Sodium Content of Fruits, Vegetables, Beans, and Legumes Average Sodium Average Sodium Fruit, Vegetable, Bean, Legume RACC (g) Content (mg/RACC) Content (mg/100 g) Banana 140 0.1 0.1 Applesauce 140 2.2 1.6 Fruit cocktail 140 4.2 3 Raisins 40 4.8 12 Frozen broccoli 85 13 15 Raw tomato 85 2.6 3 Raw cucumber 85 1.7 2 Dill pickles 30 264 879 Fresh green beans 85 0.3 0.4 Canned snap beans 130 337 259 Frozen corn 85 0.3 0.4 Canned corn 130 242 186 Baked potato 110 4.4 4 Boiled pinto beans 90 0.2 0.2 NOTE: g = gram; mg = milligram; RACC = reference amount customarily consumed. SOURCES: 21 CFR 101.12; FDA, 2007.

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 STRATEGIES TO REDUCE SODIUM INTAKE TABLE 4-11 Sodium Content of Mixed Dishes Average Sodium Average Sodium Mixed Dish RACC (g) Content (mg/RACC) Content (mg/100 g) Pepperoni pizza 140 935 668 Meatless fried rice 140 571 408 Beef burrito 140 869 621 Clam chowder 245 887 362 Chicken noodle soup 245 982 401 Frozen meal (Salisbury steak, 140 491 351 gravy, potatoes, vegetable) Quarter-pound cheeseburger 140 743 531 NOTE: g = gram; mg = milligram; RACC = reference amount customarily consumed. SOURCES: 21 CFR 101.12; 9 CFR 317.312; FDA, 2007. easily contribute significant levels to the total diet. Pepperoni pizza is a good example of this because each of the major ingredients contains sodium. The pepperoni has sodium for preservation, meat binding, and flavoring. Sodium in the cheese contributes to texture and preservation as well as taste and flavor. Tomato sauce is seasoned with salt in addition to other herbs and spices. Finally, the crust contains sodium to control the leavening process and dough stickiness. The combination of these ingredients leads to an average sodium content of 668 mg/100 g, according to FDA’s Total Diet Study market basket data (FDA, 2007). Soups are classic examples of complex, high-sodium foods. Some soups have high-sodium ingredients, such as cheese or sausage. However, even foods made from low-sodium ingredients, such as vegetables, are high in so- dium due to the use of salt for flavoring. In soups, salt contributes not only to salt taste, but also to overall flavor, as discussed in Chapter 3 (Gillette, 1985; Rosett et al., 1997). In chilled foods, sodium-containing compounds 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 (Hutton, 2002). Refrigerated or frozen meals often contain sauces or gravies. Besides contributing flavor, these sauces have a secondary role of preventing or masking warmed-over flavors. The fats in precooked meats have a tendency to experience lipid oxidation upon storage, resulting in rancid and “painty” odors and flavors (Hedrick et al., 1994). Using strongly flavored sauces can help to mask these flavors, and coating meats in sauces before storing can help to exclude the oxygen needed for these reactions to take place (Kuntz, 2000). Unfortunately, the sauces are often high in sodium.

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 ROLES OF SODIUM IN FOODS 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 salt 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 (Matz, 1993). In fried products, antioxidants may also be incorporated in these mixtures to prevent the development of rancidity (Ainsworth and Plunkett, 2007). The sodium content of selected savory snacks is shown in Table 4-12. Secondary functions of sodium in some extruded products are to mod- ify texture and color. Extruded products have a puffy texture and the degree of expansion and airiness has been found to change with the salt concen- tration of the extrudate and is thought to be due to interactions between salt and starch (a main component of these snacks). Color has also been found to change with salt content, and this relationship has been proposed to be due to the ability of salt to change the water activity of the extrudate and thus change the rate of browning reactions (Ainsworth and Plunkett, 2007). Confections As shown in Table 4-13, hard candies are generally low in sodium, and other confections may have low levels of sodium-containing leavening or texture-modifying agents (Saulo, 2002). 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 TABLE 4-12 Sodium Content of Savory Snacks Average Sodium Average Sodium Savory Snack RACC (g) Content (mg/RACC) Content (mg/100 g) Potato chips 30 147 490 French fries 70 79 113 Buttered popcorn 30 242 808 Plain popcorn 30 0.1 0.3 Hard pretzels 30 482 1,607 NOTE: g = gram; mg = milligram; RACC = reference amount customarily consumed. SOURCES: 21 CFR 101.12; FDA, 2007.

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 STRATEGIES TO REDUCE SODIUM INTAKE TABLE 4-13 Sodium Content of Confections Average Sodium Average Sodium Confection RACC (g) Content (mg/RACC) Content (mg/100 g) Milk chocolate 40 28 71 Chocolate bar with nuts 40 84 210 Lollipop 15 7.5 50 Caramel 40 94 236 NOTE: g = gram; mg = milligram; RACC = reference amount customarily consumed. SOURCES: 21 CFR 101.12; FDA, 2007. (Van der Veer, 1985). Other confections that may include salt for flavoring purposes are caramels, taffy, and nut-containing candy. Beverages Water is relatively low in sodium, but sodium levels vary by water source and with the use of water-softening systems (Bradshaw and Powell, 2002; Pehrsson et al., 2008). Tea and coffee are also very low in sodium, although the level may increase slightly with the addition of milk and cream. Sodium-containing preservatives are sometimes added to carbonated beverages and fruit drinks (Doyle et al., 2001). Even though these beverages contain sodium, the levels are generally low compared to those of many other solid food items. The vegetable juice category of beverages is one in which sodium levels are traditionally quite high. Taste and flavor improvements are the reasons for addition of salt to tomato, carrot, and vegetable blend drinks. The so- dium content of selected beverages is shown in Table 4-14. Salt is often present in sports drinks for the stated purpose of rehy- drating 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 (Jeukendrup et al., 2009; Shirreffs et al., 2007). While no data on the so- dium content of sports drinks was available from the Total Diet Study, data from USDA’s National Nutrient Database3 suggest that such drinks contain 100 mg or less per 8 oz. (240 mL) serving. It is reported that the sodium in these products is not added for taste or preservative effects (Man, 2007). 3 Available online: http://www.nal.usda.gov/fnic/foodcomp/search/ (accessed January 27, 2010).

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