MEAT, SALTED. The food industry incorporates sodium chloride (NaCl) in preservation, processing, and manufacturing operations for vegetables, poultry, fish, seafood, and meat. Although a number of food preservation techniques have been used for many years, including drying, freezing, heating, canning, filtration, enzyme treatment, high-energy irradiation, and chemicals such as organic acids, nitrate, and liquid smoke, salt remains one of the common methods of meat preservation with a long history. Salt is used to preserve meat in its dry form, as a brine, or in solution pumped into tissues (Doyle and Roman, 1982). Researchers still are examining the beneficial functional properties of NaCl in meats and other food commodities (Hajmeer, Marsden, Crozier-Dodson, Basheer, and Higgins, 1999; Pszczola, 1997).
Use of Salt in Meat and Meat Products
Sodium contents of unprocessed meat are about 55 mg/100 g of beef fiber, and 65 mg/100 g of pork fiber (Institute of Food Technologists, 1980). The level is increased when NaCl is added to the meat during processing. Salt has been used by the meat industry as a dry application and in the formulation of fermented, processed (cured or uncured), and restructured meats. Salt added to a meat system serves three main functions: extracting salt-soluble proteins, enhancing flavor, and extending the shelf life (Claus, Jhung-Won, and Flick, 1994).
Originally, in the absence of refrigeration, meat was dry-salted for extended periods of time to preserve it from microbial deterioration. Excessive salting and extended storage increased water loss, and dehydration removed water from the tissues by osmosis, lowering the water activity in the system to conditions unsuitable for microbial growth and leading to cellular plasmolysis, shrinking of cytoplasm away from the cell wall. In addition to drysalting, NaCl is incorporated in fermented meats such as semi-dry sausage during preparation. Adding NaCl prevents growth of undesirable spoilage or pathogenic microorganisms by favoring the growth of acid-producing, salt-tolerant bacteria, such as lactobacilli and micrococci. Production of acid by these microorganisms gives the meat a desirable tangy flavor and lowers the pH of the system, which adds another safeguard against the growth of undesirable microorganisms.
In processed comminuted meats, for example, bologna, frankfurters, and summer sausage, and noncomminuted meats, for example, ham, bacon, and pastrami, NaCl is one of the basic ingredients, after the meat itself. Other ingredients include water, spices, nonfat dry milk, sweeteners, phosphates, and nitrite. Salt and nitrite are the main ingredients used to cure meats and are applied dry, by immersion, or by injection methods. Salt added to processed meats helps to extract NaCl-soluble proteins, increases the gel strength of the emulsion or batter, enhances the flavor, inhibits or minimizes microbial growth, and enhances antimicrobial activity of other compounds in the system. Salt-soluble proteins coat the fat molecules in the system and provide a stable emulsion, which is important in improving moisture retention and texture of the final product (Claus et al., 1994). Salting prerigor hot-boned meat to be further processed, for example, when making sausage, helps maintain its water-holding capacity (WHC) and fat-emulsifying properties (Hamm, 1981).
Salt, in conjunction with sodium tripolyphosphate, is used for protein extraction in the preparation of restructured meats, which are sectioned and formed noncured products. Restructuring meats makes it feasible to use lower-grade, less expensive cuts and, similar to the concept of processing meats, restructuring them provides more diversified products that are flavorful, nutritious, affordable, and convenient.
Salt can be encapsulated with partially hydrogenated vegetable oil to prevent excess extraction of salt-soluble proteins during meat processing. This eliminates undesirable changes in meat texture and viscosity. Encapsulated salt used in sausage preparation produces desirable qualities such as high moisture, crumbly and tender texture, and good flavor (Pszczola, 1997). Normally, 2 to 3 percent NaCl is added during the chopping or emulsifying process to help extract the proteins, but this amount may range from as little as 1.5 to 5.0 percent (Claus et al., 1994).
Advantages, Disadvantages, and Limitations of NaCl
Salt enhances the flavor of meat by suppressing undesirable or unpalatable savors. It extends the shelf life by retarding microbial growth because it exerts both bactericidal and bacteriostatic effects on many microbes found in meat (Marsden, 1980). This might be associated with changes in water activity and ionic strength that render water unavailable to microorganisms (Hajmeer et al., 1999). Other factors include dehydration, the direct effect of chlorine ions, removal of oxygen from the medium, sensitization of microorganisms to carbon dioxide, and interference with the rapid action of proteolytic enzymes (Polymenidis, 1978).
Spoilage and pathogenic bacteria such as Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, Clostridium botulinum, and lactic acid bacteria have various tolerances and differ in their responses to salt. Among other factors, these depend on microbial tolerance to NaCl, type and concentration of NaCl, exposure time, pH, and temperature. Salmonella spp., S. aureus, and C. botulinum have the ability to grow in brine solutions with high salt concentrations and at low temperatures (Marsden, 1980). Therefore, using a combination of ingredients and processing methods, such as the curing process, that employ both NaCl and nitrite is important in controlling microbial growth.
Excess use of NaCl has undesirable effects on the flavor, color, and appearance of meat. Application of dry NaCl, for example, can result in an unattractive and darker color of lean (Pearson and Gillett, 1999). As a powerful prooxidant, NaCl has undesirable oxidative effects on meats. Processed frozen products containing salt become rancid and produce unacceptable flavors during extended storage (Claus et al., 1994). Incorporation of other ingredients in the meat system, such as sugar, nitrite, and antioxidants, for example, butylated hydroxyanisole (BHA) helps minimize or control these negative effects by masking adverse flavors, preventing color degradation, and reducing oxidative properties. Salt can have a synergistic effect and enhance the activity of other preservatives such as BHA (Stern, Smoot, and Pierson, 1979). However, impurities in NaCl can reduce its effectiveness in extracting NaCl-soluble proteins because they interfere with the WHC and emulsifying properties of the meats. Therefore, it is important to use a purified grade of NaCl.
Because of increased concerns regarding high salt intake and its role relative to hypertension, high blood pressure, and potential heart disease, public health authorities recommend reduction in NaCl intake (IFT, 1980). Intake can be reduced by lowering its levels during processing or by substituting potassium chloride (KCl) for part of the NaCl (Pearson and Gillett, 1999). Unfortunately, reduction of NaCl in meat products weakens its preservative capacity and the binding and WHC of the systems. Furthermore, complete replacement of NaCl with KCl is undesirable because of the aftertaste left by KCl. Polyphosphates and other chloride salts also can be used to replace NaCl.
NaCl levels in the diet have been of some concern, and maintaining public health is a priority. Salt use cannot be eliminated completely in the meat industry to reduce health risks because of the important technological functions it performs. It is important to determine the minimum levels of NaCl necessary to maintain its functionality while addressing the health concerns of consumers.
See also Fish, Salted; Game; Hunting and Gathering; Iodine; Mammals; Meat; Military Rations; Preserving; Salt; Sodium .
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Maha N. Hajmeer James L. Marsden