A Fresh Look at Food Safety
Linda Milo Ohr
The call for clean labels has food processors to seek ‘natural’ antimicrobials and shelf life extenders.
During my days of working for an analytical food laboratory, I witnessed firsthand the havoc that spoilage microorganisms, mold and pathogens can cause when they are left unchecked in foods. Thanks to countless shelf life and challenge studies, I can no longer eat reified beans or bagged salads without envisioning their appearance after they’ve surpassed their predicted shelf life or been inoculated with the likes of Listeria, E. coli and Salmonella.
Fortunately for the food industry, preservatives such as sorbates, benzoates and acidulants are available to extend shelf life and reduce contamination. However, the demand for clean labels has spurred the growth of foods that are minimally processed or. claim to contain no preservatives. According to New Product News, the number of products flagged as having no additives or preservatives topped 300 in 1999, more than double the previous year. Many of these products are found in natural food stores and include bakery dairy, meals and additive-free meat products such as lunchmeat and sausage.
Consumers, blissfully unaware of the steps that must be taken to ensure the safety of clean-label foods, continue to demand such products. As a result, processors have spent considerable time and effort learning how to use ingredients that extend shelf life while still appeasing the call for all natural and “uncomplicated” labels. Some function as additional hurdles while others hold promise for future use.
Spice Power
In addition to boosting flavor, spices have long been known to possess antimicrobial properties. Much research has focused on these properties, but it was not until recently that studies looked specifically at spices and their effect on Escherichia coli O157:H7 in food.
Daniel Fung, Ph.D., professor of food science at Kansas State University, and his students Erdogan Ceylan and Judith Sabah conduct research using this pathogen. Fung recently studied the antimicrobial properties of 23 spices in McConkey sorbitol agar (MSA), ground beef and salami, all inoculated with E. coli O157:H7. He found that garlic had the most antagonistic effect in MSA and salami, while clove had the highest activity against O157:H7 in ground beef.
“In meat products, more than 1% by weight of garlic is effective at controlling E. coli O157:H7. Some food already contains 3% garlic, so it is feasible to use garlic as an additional barrier to contamination,” says Fung.
Fung took the study further and looked at the relationship between garlic and heating in ground beef inoculated with the pathogen. The study indicated that in the case of undercooking, the presence of garlic results in added protection. Additionally, the antagonistic effect of garlic increased as the cooking temperature increased.
“Garlic contains allicin and other sulfide compounds that suppress organisms,” explains Fung. Other spices exhibited antimicrobial effects against E. coli O157:H7 in ground beef. They include clove, which contains eugenol and caryophyllene; sage, which contains picrosalvin, carnosol and cineole; and oregano, which contains thymol, carvacrol and borneol.
Fung has also investigated the antimicrobial effects of cinnamon, which contains cinnamaldehyde and eugenol, when added to pasteurized apple juice inoculated with E. coli O157:H7. His work showed that 0.3% cinnamon has an inhibitory effect on E. coli O157:H7 stored for 3 days at 25[degrees]C. The same concentration is effective at 8[degrees]C for up to 8 weeks.
In addition to functioning as antimicrobials, the phenolic compounds present in these spices also function as antioxidants. Spices have been found to be effective in retarding rancidity during frozen storage of ground meat. Rosemary extract, for example, has found commercial application as a natural antioxidant in products such as beverages and meats.
Bacteria vs. Bacteria
Certain bacteria serve as sources of natural antimicrobials and shelf life extenders. Some function by producing antimicrobial substances such as bacteriocins or fermentation end products. Others inhibit the growth of harmful pathogens by competing directly for the resources they need to survive.
Bacteriocins are antimicrobial proteins produced by both Gram-positive and Gram-negative species. They generally exert a bactericidal effect only against closely related species of bacteria. The most obvious way to incorporate bacteriocins into a food formulation is to isolate the natural active antimicrobial, purify it, and use the resulting ingredient as a direct FDA-approved additive.
Two approved bacteriocins include nisin and natamycin. Produced by a strain of Streptomyces natalensis, natamycin displays an antimycotic effect against yeast and molds. It is approved for preventing mold growth on the surface of cheese.
Nisin is a peptide derived via fermentation. It is bactericidal against a variety of Gram-positive bacteria. Research at Ohio State University showed that nisin acts as a bactericidal agent against vegetative cells of Clostridium botulinum, whereas its mode of action against the spores is sporostatic.
Nisin functions by interacting with the phospholipids in the cytoplasmic membrane of bacteria, thus disrupting membrane function. With spores, nisin prevents outgrowth by inhibiting the swelling process of germination. The Food and Drug Administration has approved the addition of commercially prepared nisin to pasteurized cheese and processed cheese spreads.
Formulators can “indirectly” apply bacteriocins and other antimicrobials to fermented products through the use of cultures. For example, if a microorganism used in the manufacture of a fermented dairy food possesses the capability to synthesize a hacteriocin, the dairy food has its own built-in food preservation system. This allows for a cleaner label on the final food product.
One ingredient company supplies a meat starter culture that specifically reduces Listeria monocytogenes numbers in fermented sausage. It can be labeled as “lactic acid starter culture,” says Fred Borsa, technical services specialist, seasonings business unit for the supplier.
The bactericidal effect is due to the production of bacteriocins by the respective lactic meat starters, a blend of Pediococcus and Lactobacillus strains. Without subsequent heat treatment, the culture blend demonstrates 3-5 log reductions in L. monocytogenes in typical fermented sausage. With subsequent heat treatment to 1280F, a total Listeria kill of 5+ logs is observed.
“The real inhibition from these cultures comes from the bacteriocins each one produces,” Borsa explains. Secondary inhibition results from lactic acid production and competition.
Cultured whey is another cleanlabel ingredient that extends shelf life. Borsa’s company has developed a line of natural mold inhibitors that can be customized to individual requirements. The mold inhibitors are produced by fermentation with selected food-grade microorganisms.
“We use whey as the fermentation substrate, resulting in the production of primarily calcium propionate. The organisms we choose are propionic bacteria that form this calcium salt,” he explains. A small amount of acetate is another fermentation end product.
“Since the active ingredients in the cultured whey are propionates and acetates, applications are widespread for our natural mold inhibitors,” says Borsa. They can be formulated into seasoning blends or sprayed directly on the finished product surface. The mold inhibitors are ideal ingredients in formulations for jerky, sausage products, sauces, marinades, breads and other bakery products.
“In a dough formulation, you would typically mix 0.5% per weight of flour in with the dry ingredients. One of our studies showed general mold inhibition throughout a 90-day shelf life,” states Borsa. At 0.4% inclusion, the natural mold inhibitors resulted in beef jerky with a shelf life up to 4 months.
Non-dairy mold inhibitors are also available. Instead of whey, Borsa’s company might use cultured corn syrup solids or cultured dextrose as the substrate.
Natural Barrier Films
In addition to acting as fermentation substrates, whey proteins show potential as oxygen, aroma and oil barrier films at low to intermediate relative humidity (RH). Research conducted by John Krochta at the California Dairy Foods Research Center, University of California-Davis, showed that whey protein films provide durability when used as a coating on food products or films separating layers of heterogeneous foods.
The formulation of disulfide bonds and ionic bonding controlled by calcium ions helps build the structure of clear whey protein-based gels. With appropriate heating conditions, whey proteins contribute to favorable viscosity and heat-setting gel characteristics. Potential applications include lipid barrier films or coatings separating lipid-rich ingredients from other components of heterogeneous foods; and oxygen or aroma barrier coatings for low-moisture food products when used in conjunction with a simple, moisture-barrier packaging film.
“Whey protein film can be formed as a coating on nuts or other products that suffer from oxygen intrusion. By inhibiting oxidation, whey protein protective coatings help improve the quality and shelf life of nuts and such nut-containing products as confections and baked goods,” says Krochta.
The whey protein films could potentially eliminate the use of synthetic oxygen/aroma barriers in multi-layer packages, reduce food loss due to damage and extend shelf life. The California Dairy Foods Research Center is currently looking to license the edible films.
Adjusting the Hurdles
In addition to these ‘clean label’ antimicrobials and shelf life extenders, simple manipulation of processing, storage and formulation parameters can also help ensure safer foods.
“Think about the tried-and-true methods for preventing spoilage or maintaining foods in a safe manner,” advises Joe Shebuski, Ph.D., senior microbiologist program leader for an analytical food laboratory. “Be concerned about storage time and temperature, avoiding optimum environmental conditions for organisms to grow.”
For example, minimally processed refrigerated products should be maintained as cold as possible throughout the manufacturing and distribution channels in order to minimize growth, says Shebuski. “Refrigeration acts as the primary barrier in these products. If temperature abuse occurs, there is potential for pathogen growth and reduced shelf life.”
Adjusting pH and water activity of products provides additional hurdles for spoilage organisms or pathogens to overcome, says Shebuski. Fruit purees or juices can “naturally” lower pH in products that are compatible. An article in Trends in Food Science and Technology cited several examples of using hurdle technology. In tortellini, for example, reduced water activity and mild heating are the principal hurdles employed during processing, in addition to a modified atmosphere or ethanol vapor in the package and chilling of the product during storage and retail display. Used in combination with novel processing techniques and “natural” antimicrobials, these adjustments can result in safe and wholesome products that carry the clean labels consumers demand.
Technologies for Meat Safety
Researchers at the California State Polytechnic University-Pomona may have discovered a new way to remove harmful bacteria from meat surfaces. The breakthrough involves applying a small amount of lactoferrin (isolated from whey) to the surface of meat during processing.
“We borrowed a page from Mother Nature,” states Dr. A.S. “Narain” Naidu, a medical microbiologist who heads the Center for Antimicrobial Research at Cal Poly Pomona. “We have taken a natural compound with antimicrobial properties and discovered a way to make it work on meat surfaces to provide a protective barrier against harmful bacteria.”
Lactoferrin is a naturally occurring protein in mammalian milk that has been shown to protect infants from infectious bacteria while their immune systems are developing.
The university’s research involved applying an activated form of lactoferrin to meat tissues that had been deliberately contaminated with high concentrations of bacteria. Laboratory tests confirmed that the activated lactoferrin was effective in removing more than 30 pathogens, including E. coli O157:H7, Salmonella and Campylobacter.
By not being able to attach themselves to the meat’s surface, the bacteria starve and fail to multiply or produce harmful toxins.
According to Naidu, the amount of activated lactoferrin required to protect a serving of meat is thousands of times less than the amount of lactoferrin found in a single glass of milk.
In a typical meat processing plant, the activated lactoferrin could be spray applied as a final step in the carcass-sanitizing process, or it could be applied to ground beef or other end products using available application technology. Because lactoferrin remains on the meat’s surface, the compound may keep bacteria from binding to the surface for an extended time period.
Research funding and support were provided by Farmland National Beef (FNB), which intends to incorporate lactoferrin into its operations once regulatory approvals are granted. The Kansas City-based beef processor estimates that it may take up to 18 months before the technology is approved commercially. FNB plans to develop a package seal to promote its meat products that are protected with activated lactoferrin.
Along with carcass treatments, HACCP, GMPs and proper sanitation practices, meat processors now have a new weapon to ensure a safe meat supply. On February 22, 2000, the USDA issued a final rule permitting the use of ionizing radiation for the treatment of refrigerated or frozen uncooked red meats and meat products.
Irradiation, which is defined as a food additive under FDA regulations, can reduce or eliminate many food pathogens, including E. coli, Salmonella and Listeria.
In early March, Colorado Boxed Beef Co. became one of the first meat processors to offer an irradiated ground beef product for retail and foodservice markets. “With E. coli being such a killer bug and having such a stigma within the industry and the public, we wanted to add this extra measure of safety;’ declares Steve Saterbo, co-owner of Colorado Boxed Beef.
Under its New Generation label, the Auburndale, Fla., company plans to market irradiated frozen ground beef patties in a 2-lb. box, and fresh ground beef in a 1-1.5 lb., case-ready MAP tray with a 10-day shelf life and a 1.5-lb. chub package.
Colorado Boxed Beef contracted with FoodTechnology Service, Mulberry, Fla., to irradiate the ground beef. “We are convinced that the gamma irradiation process best preserves the integrity and taste of the ground beef and it offers more options,” reports Saterbo.
To date, several major supermarket chains have requested samples of the irradiated products. “We are offering the retailer an opportunity to take his own taste test,” notes Saterbo. None of the retailers, however, have committed to stocking Colorado’s irradiated beef. But things may be changing.
In late February, Wal-Mart announced that it would test market irradiated beef products at a “handful” of its stores to determine consumer demand and pricing.
Bob Swientek, Editor-In-Chief
COPYRIGHT 2000 Cahners Publishing Company
COPYRIGHT 2000 Gale Group
