Validation of a traditional Italian-style salami manufacturing process for control of salmonella and Listeria monocytogenes

Italian-style salami batter (formulated with pork shoulder) was inoculated with ca. 7.0 log CFU/g of either Salmonella or Listeria monocytogenes. Salami links (55-mm cellulose casings) were fermented at 308C for 24, 40, or 72 h and then dried to target moisture/protein ratios (MPRs) of 1.9:1 or 1.4:1. Links were sampled after fermentation (24, 40, and 72 h) and after combined fermentation-drying treatments (MPRs of 1.9:1 and 1.4:1 for all fermentation periods), and microbiological and proximate analyses were performed at each sampling. Pathogen populations were enumerated by direct plating on selective agar and by an injured-cell recovery method. When enumerated by the injured-cell recovery method, Salmonella populations were reduced by 1.2 to 2.1 log CFU/g after fermentation alone (24 to 72 h) and by 2.4 to 3.4 log CFU/g when fermentation was followed by drying. Drying to an MPR of 1.4:1 was no more effective than drying to an MPR of 1.9:1 (P . 0.05). When enumerated directly on selective media, Salmonella populations were reduced from 1.6 to 2.4 log CFU/g and from 3.6 to 4.5 log CFU/g for fermentation alone and fermentation followed by drying, respectively. L. monocytogenes populations were reduced by ,1.0 log CFU/g following all fermentation and combined fermentation-drying treatments, regardless of the enumeration method. These results suggest that the Italian-style salami manufacturing process evaluated does not adequately reduce high pathogen loads. Processors may thus need to consider supplemental measures, such as raw material specifications and a final heating step, to enhance the lethality of the overall manufacturing process

Use of Oxyrase® enzyme to enhance recovery of Escherichia coli O157:H7 from culture media and ground beef

Escherichia coli O157:H7 is a bacterium that has caused great concern in the meat and food industry during the last few years because of several, well-publicized, disease outbreaks, including the incident at the Jackin- the-Box fast food chain in Seattle, Washington. The organism can cause severe sickness and even death in certain population groups. To better assure meat safety, federal meat inspection is focusing on developing rapid methods to detect this disease agent and others. Oxyrase is a commercially available enzyme that can accelerate the growth of some bacteria. Current techniques for isolation and culturing of E. coli O157:H7 from foods require an enrichment period of 18 to 24 hours, thus limiting their usefulness for perishable foods that are marketed quickly. Our investigation found that Oxyrase shortened required enrichment periods in broth culture only. The enzyme was less effective in sterilized ground beef

Effects of cetylpyridinium chloride treatment of roast beef on Listeria monocytogenes populations and quality attributes

The effectiveness of cetylpyridinium chloride (CPC) for reducing microbial populations, in particular Listeria monocytogenes, on ready-to-eat roast beef was evaluated. Roast beef slices inoculated with L. monocytogenes were dipped in a solution of 1% CPC for 1 minute. Samples were then vacuum packaged and stored at refrigeration temperature. The effects of CPC treatment on microbial populations, as well as on color and texture of the roast beef samples, was evaluated over a 42-day period. Immediately after CPC treatment, L. monocytogenes populations were reduced by 99 to 99.99%, with the treatment being somewhat more effective on exterior than on sliced/cut surfaces. Throughout 42 days of refrigerated storage, populations of L. monocytogenes, total bacteria, and lactic acid bacteria remained lower on CPC-treated samples than on non-treated samples. Treatment with CPC did not significantly affect the color or texture of roast beef. Treatment with CPC, especially when applied to products before slicing, may serve as an effective antimicrobial intervention for ready-to-eat meat products

Microbial flora of commercially produced vacuum packaged, cooked beef roast

Commercially produced vacuum packaged, fully cooked, microwaveable beef roasts from four producers were purchased from local retail markets. Salt concentration, pH, water activity (aw), and percent moisture, fat and protein were determined. Samples of both package juice and homogenized beef plus juice were analyzed for the presence of aerobic, anaerobic and lactic acid bacteria and clostridia-type organisms. The cooked beef products had pH values from 5.82 to 6.19, water activity of 0.992 to 0.997, and contained 0.34 to 1.07% salt, 61.89 to 72.39% moisture, 4.29 to 18.21% fat and 15.92 to 20.62% protein. No growth was detected in juice for aerobic, anaerobic or lactic acid bacteria or clostridia-type organisms. Combined beef and juice had less than 2 CFU/g for aerobic, anaerobic or lactic acid bacteria or clostridia-type organisms. Cooking and chilling schedules used in the manufacture of the four products we evaluated in this study limited survival and outgrowth of microorganisms

Validation of a steam based post-process pasteurization system for control of Listeria monocytogenes in ready-to-eat roast beef

Listeria monocytogenes has been implicated in outbreaks of illness involving ready-to-eat (RTE) meat products, prompting researchers to look into intervention technologies to reduce or eliminate this risk. In our study roast beef was inoculated with a 5-strain cocktail of Listeria monocytogenes, vacuum-packaged, and then pasteurized at 205°F for 0, 2, 3 or 4 min in a Stork RMS-Protecon Post-Process Pasteurization System. More bacteria were killed as pasteurization time increased. Initial inoculum level was 5.8 log10 CFU/cm2 of product surface area. Pasteurization for 2 min resulted in 2.5 to 2.7 log10 CFU/cm2 reductions. Similar reductions were seen at 3 min. At 4 min pasteurization, L. monocytogenes decreased in roast beef by approximately 4.5 log10 CFU/cm2; over 99.99% had been killed. The Stork steam based system is effective for reducing the risks of L. monocytogenes in RTE roast beef while providing acceptable quality characteristics

Evaluation of consumer reheating methods for destruction of Listeria monocytogenes in frankfurters

The USDA Food Safety and Inspection Service has issued a “zero tolerance” for Listeria monocytogenes in ready-to-eat meat and poultry products. The Food Safety and Inspection Service recommends that consumers “Reheat [hotdogs] until steaming” to reduce the risk of listeriosis. We evaluated L. monocytogenes survival on inoculated frankfurters after reheating using common, in-home consumer practices. Frankfurters were inoculated with a six-strain mixture of L. monocytogenes to an initial level of approximately 107 colony forming units (CFU)/gram. Eight inoculated franks for each treatment were cooked using boiling water, a conventional electric oven, or a microwave oven. L. monocytogenes recovery was calculated after plating on Modified Oxford Agar and Tryptose Phosphate Agar. L. monocytogenes reductions were 3.2 log10 CFU/gram on franks microwaved with or without water for 60 seconds or cooked in a conventional electric oven at 500°F for 2 or 5 minutes. Franks cooked in boiling water for 30 and 60 seconds achieved reductions of 4.3 and 4.9 log10 CFU/gram, respectively. Franks wrapped in a paper napkin and microwaved for 60 seconds resulted in a 6.8 log10 CFU/gram reduction, the most effective consumer reheating protocol

Control of Listeria Monocytogenes in ready-to-eat meats using cetyl pyridinium chloride

Cetyl Pyridinium Chloride (CPC) spray using variable application temperatures, pressures, and times was evaluated for its effectiveness in reducing Listeria monocytogenes inoculated on the surfaces of commercial frankfurters and Polish sausage. Frankfurters and Polish sausage were inoculated with a five-strain cocktail of L. monocytogenes (101M, 109, 108M, serotype 4c ATCC, and serotype 3 ATCC) and subjected to no treatment, CPC treatment, and CPC followed by water treatment. CPC (1%) was applied to the frankfurters and Polish sausage by spraying in a cabinet using all combinations of 77, 104, and 131°F spray temperatures; 20, 25, and 35 psi spray pressures; and 30, 40, and 60 second times of exposure. No individual effect (P>0.05) of any particular application temperature, pressure, or time on the reduction of L. monocytogenes was observed. Hardness and color of the product was not affected when treated with 1% CPC. From initial inoculum levels of 8.20 log colony forming units (CFU)/gram, 1% CPC reduced L. monocytogenes by 1.19 to 2.39 log CFU/gram

Escherichia Coli O157:H7 risk assessment for production and cooking of restructured beef steaks

Distribution of Escherichia coli O157:H7 in restructured beef from artificially inoculated meat pieces and destruction of E. coli O157:H7 in restructured beef steaks prepared from artificially inoculated meat was evaluated following broiling and grilling. In Study I, longissimus dorsi trimmings were inoculated with fluorescently marked E. coli O157:H7 cells to microscopically identify bacterial distribution throughout restructured steak cross-sections. E. coli O157:H7 fluorescent density was observed along the glue lines where meat pieces were enzymatically attached. Study II quantified the level of E. coli O157:H7 throughout the entire thickness of restructured beef. Cross-sectional slices of core samples from the steaks showed that bacterial contamination was evenly distributed (ca. 106 CFU/g). Study III determined the extent of E. coli O157:H7 reduction achieved during cooking. Beef trimmings were inoculated to a level of 107 CFU/g and used to prepare restructured beef chubs. Restructured steaks of three thicknesses (0.5, 1.0, and 1.5 inches) were sliced from the chubs and cooked to one of six target internal temperatures (120, 130, 140, 150, 160, or 170°F) by commercial gas grill or oven broiler. Broiling was more effective than grilling, although E. coli O157:H7 survival decreased as endpoint temperatures increased incrementally. To achieve an adequate level of safety confidence, restructured steaks should be cooked in a manner similar to ground beef; to an internal temperature of at least 160°F

Escherichia coli O157:H7 risk assessment for blade-tenderized beef steaks

The potential translocation of E. coli O157:H7 from the surface to the interior of whole muscle by blade tenderization was evaluated. Beef top sirloin subprimals were inoculated with 106 or 103 cfu/cm2 and passed once through a Ross blade tenderization unit. Core samples showed a translocation of 3 to 4% of surface inoculum to the geometric center of the subprimal. A second study evaluated thermal destruction of E. coli O157:H7 in blade tenderized (BT) steaks compared to nontenderized (NT) steaks of three thicknesses when ovenbroiled. Subprimal surfaces were inoculated to a level of 107 cfu/cm2 and blade tenderized. Steaks cut from these subprimals were ovenbroiled to internal temperatures from 120 to 170°F, then analyzed for surviving E. coli O157:H7. At internal steak temperatures of 140°F and higher, all E. coli O157:H7 were killed in both BT and NT steaks of all thicknesses. At 130°F, about 5 log reductions were noted for both BT and NT. With oven broiling to even moderate internal temperatures, BT steaks pose no greater risk of E. coli O157:H7 infection than NT steaks

Post-process steam pasteurization of packaged Frankfurters combined with acid/buffer treatments for control of Listeria monocytogenes

The efficacy of a saturated steam-based post-process pasteurization system to reduce/ eliminate Listeria monocytogenes on frankfurters was evaluated. Frankfurters were packaged individually or in a single layer format (4 per package, touching). Samples were surface treated with 2% lactic acid, 4% lactic acid, 2% buffered sodium citrate, or 2% buffered sodium lactate, vacuum packaged, and steam pasteurized to end-point surface temperatures of 160, 170 or 180°F using a Townsend Post-Process Pasteurization system (formerly Stork-RMS Protecon). Pasteurization of inoculated single layer franks to surface end point temperature targets of 160, 170, and 180°F resulted in L. monocytogenes reductions (P0.05) were noted between various surface acid treatments applied. Post-process pasteurization of frankfurters (in-package) using the saturated-steambased Townsend system was effective in reducing numbers of L. monocytogenes