Growing sales in both the U.K. and the U.S. indicate refrigerated foods continue to please consumers seeking foods that provide convenience and quality benefits. These products are processed to less than sterile conditions and require little to no consumer preparation time.

Granted, convenience and flavor are major selling points, but the safety of these products is of utmost importance. Processors must formulate meat products to prevent the growth of both spoilage microorganisms and pathogens such as Listeria monocytogenes. Fortunately, ingredient suppliers provide an arsenal of antimicrobials and antioxidants that promote the safety and sensory quality of processed meat and poultry products. Some are tried and true, while newer ingredients and technologies are increasing in usage.

Processors must formulate meat products to prevent the growth of both spoilage microorganisms and pathogens such as Listeria monocytogenes.

Safety Line-up

In processed meats, some of the staple ingredients include salt, phosphate, lactates, acetates and ingredients that possess antioxidant capabilities, while other components—such as spices—are finding multiple functions as flavor enhancers.

Lactates. Lactates are salts (e.g., potassium or sodium) of lactic acid. There are several theories into the exact mechanism of how these organic acids interfere with cell metabolism. The pH reduction that occurs is likely to be one important factor.

The lag phase of bacterial growth for a number of pathogens including Listeria and Salmonella is increased, says M. Susan Brewer, associate professor, food science and human nutrition, University of Illinois, Champaign. Brewer adds that lactates are permitted at up to 4.8%, but common usage levels tend to be in the 1.8-3.0% range.

Research at Kansas State University, Manhattan, Kansas, indicates that when lactates are put into solution and injected into products such as steaks and roasts, the best use level is at approximately 0.2%, says Curtis Kastner, professor, meat science. “Lactates in meat products preserve flavor and help control microbial growth,” he adds.

Acetates. “Diacetates are salts of acetic acid,” says Brewer. “They are bacteriocidal against spoilage organisms and some pathogens—by immediately lowering the pH and reducing the initial microbial load. “They are used at 0.25% but, sometimes, result in off-flavors.” Combining lactates and diacetates allows for lower usage levels of both, which reduces the chance for undesirable flavors.

Salt. Salt restricts the available water in a meat product (i.e., lowers Aw), inhibiting microbial growth. Salt long has been used as a meat preservative. In addition, it solubilizes proteins and contributes to the texture of processed meats.

“Salt is a functional ingredient in emulsified meat products such as hot dogs,” explains Brewer. “These products are emulsions of meat fat droplets surrounded by meat protein, all suspended in the water phase of the meat. In order to surround the fat droplet, the meat protein must be pulled out of the muscle cells. Salt functions to extract the meat protein from the cells.”

Nitrites. Nitrites are used for flavor and color development, as well as for their antimicrobial activity. They inhibit the growth of Clostridium botulinum and a variety of other bacteria. Sodium nitrite has been used in the curing and preservation of processed meats for centuries.

Today, meat processors use sodium ascorbate or sodium erythorbate, in combination with lower levels of nitrites to control microbes.

Chelators. Ingredients that assist in reducing oxidation in processed meats include alkaline phosphates and sodium erythorbate. Usage levels vary, but typical levels are between 0.25 and 0.40%, according to Kastner.

“(Certain) ingredients chelate metal ions, such as iron, from the meat pigment myoglobin,” states Brewer. “Under the right conditions, some metal ions, including iron, are powerful pro-oxidants. Binding them reduces their ability to initiate oxidation of the fats, which results in off-odor and off-flavors.”

Demands for reduced-salt and lowfat meat products pose challenges for food formulators.
Organic acids. Acetic, lactic, and some other organic acids can be used in very specialized products to lower pH, says Brewer; however, reducing the pH below 5.7 impacts the meat's water-holding capacity. Formulators usually add organic acids in “encapsulated” form. The addition of microbial cultures (such as lactic acid bacteria) to fermented meat products, along with a source of fermentable carbohydrate, also results in bacterial production of lactic acid.

Spices. Increasing research points to both the antioxidant and antimicrobial properties of certain spices. “Antioxidant fractions extracted from spices and herbs (rosemary) are mostly phenolic substances, which allow themselves to be “sacrificed” to the oxidative process and, thereby, protect the fats in the meats and delay the onset of oxidation,” says Brewer.

Past research at Kansas State University studied the antimicrobial properties of various spices. Garlic contains allicin and other sulfide compounds that suppress organisms. Other spices exhibiting antimicrobial properties include clove, which contains eugenol and caryophyllene; sage, which contains picrosalvin, carnosol and cineole; and oregano, which contains thymol, carvacrol and borneol.

Trends and Technologies

Although popular among health-conscious consumers, reduced-salt and lowfat meat products pose challenges for food formulators. Lowering salt content increases the available water. Lowfat products also are generally higher in water content, notes Brewer. Since moisture is a major determinant of microbial growth, increasing the water content (i.e., increasing Aw) increases risk of microbial spoilage. Other hurdles to microbial growth become more critical.

Newer technologies—such as high-pressure processing and vacuum packaging—will help overcome the problem of spoilage and pathogenic microorganism growth, notes Brewer.

Products also will be improved by pumping in a solution of salt, phosphate, and/or flavor enhancers, a newer method utilized in lean, whole muscle cuts. The salt and phosphate hold water, while salt and flavor enhancers increase flavor profile.

Another technology, post-process pasteurization, eliminates surface contamination after final packaging, states Kastner. “In wieners, for example, you remove the casing after they come out of the smokehouse. There is risk of surface contamination at this point, before they are finally packaged. With post-process pasteurization, you package the wieners and make sure they are not touching each other, run them through a steam chamber or hot water, and post-process pasteurize them. This will eliminate surface contamination.”

No matter what trend one is trying to satisfy or what antimicrobial or technology is being utilized, Kastner reminds formulators that the ultimate challenge is to make sure the meat product has the appropriate shelf-life and gets properly handled and processed to control microorganisms.