The purpose of this paper is to provide guidance to food processors in controlling Listeria monocytogenes in food-processing environments. Of particular concern are outbreaks of a few to several hundred scattered cases involving an unusually virulent strain that has become established in the food-processing environment and contaminates multiple lots of food over days or months of production. The risk is highest when growth occurs in a food before it is eaten by a susceptible population. The information presented in this paper provides the basis for the establishment of an environmental sampling program, the organization and interpretation of the data generated by this program, and the response to Listeria-positive results. Results from such a program, including examples of niches, are provided. Technologies and regulatory policies that can further enhance the safety of ready-to-eat foods are discussed.

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Meat and poultry products frequently have been implicated in outbreaks of foodborne illness. The risk of foodborne illness can be reduced through implementation of the hazard analysis critical control point (HACCP) concept. The basic principles of HACCP described by the International Commission on Microbiological Specifications for Foods are briefly reviewed. Examples are presented to describe how these principles can be used to manufacture meat and poultry products with improved microbiological safety and quality. The future acceptance of HACCP will depend on the resolution of certain issues.

In January 1999, the Food Safety and Inspection Service (FSIS) finalized performance standards for the cooking and chilling of meat and poultry products in federally inspected establishments. More restrictive chilling (stabilization) requirements were adopted despite the lack of strong evidence of a public health risk posed by industry practices employing the original May 1988 guidelines (U.S. Department of Agriculture FSIS Directive 7110.3). Baseline data led the FSIS to estimate a "worst case" of 10(4) Clostridium perfringens cells per g in raw meat products. The rationale for the FSIS performance standards was based on this estimate and the assumption that the numbers detected in the baseline study were spores that could survive cooking. The assumptions underlying the regulation stimulated work in our laboratory to help address why there have been so few documented outbreaks of C. perfringens illness associated with the consumption of commercially processed cooked meat and poultry products. Our research took into account the numbers of C. perfringens spores in both raw and cooked products. One hundred ninety-seven raw comminuted meat samples were cooked to 73.9 degrees C and analyzed for C. perfringens levels. All but two samples had undetectable levels (<3 spores per g). Two ground pork samples contained 3.3 and 66 spores per g. Research was also conducted to determine the effect of chilling on the outgrowth of C. perfringens spores in cured and uncured turkey. Raw meat blends inoculated with C. perfringens spores, cooked to 73.9 degrees C, and chilled according to current guidelines or under abuse conditions yielded increases of 2.25 and 2.44 log10 CFU/g for uncured turkey chilled for 6 h and an increase of 3.07 log10 CFU/g for cured turkey chilled for 24 h. No growth occurred in cured turkey during a 6-h cooling period. Furthermore, the fate of C. perfringens in cooked cured and uncured turkey held at refrigeration temperatures was investigated. C. perfringens levels decreased by 2.52, 2.54, and 2.75 log10 CFU/g in cured turkey held at 0.6, 4.4, and 10 degrees C, respectively, for 7 days. Finally, 48 production lots of ready-to-eat meat products that had deviated from FSIS guidelines were analyzed for C. perfringens levels. To date, 456 samples have been tested, and all but 25 (ranging from 100 to 710 CFU/g) of the samples contained C. perfringens at levels of <100 CFU/g. These results further support historical food safety data that suggest a very low public health risk associated with C. perfringens in commercially processed ready-to-eat meat and poultry products.

This review supplements the review by Hargreaves et al. (1972). Phosphate selection in the U.S. continues to be based upon achieving specific functional objectives other than microbial control. Current federal regulations limit the addition of phosphates to those levels which will achieve functionality. One notable exception is shelf stable pasteurized process cheese, cheese food, and cheese spreads. Adding relatively high levels of phosphates for emulsification coincidentally provides microbiological stability; however, the minimum levels for stability remain uncertain. It is becoming increasingly evident that phosphates, under certain conditions, have potential value for enhancing the microbial safety and stability of foods. Certain phosphates or mixtures of phosphates are clearly more effective than others. Through future research, it should be possible to further exploit the potential value of phosphates. This review offers direction for such research.

In an effort to reduce the initial levels of nitrite used to cure bacon and still supply the botulinal inhibition expected in cured meats, bacon was produced at nitrite levels of 0 and 40 ppm NaNO2 with and without 0.13 and 0.26% potassium sorbate. This bacon was inoculated with 1100 spores per g of a mixture of five Type A and five Type B strains of Clostridium botulinum. The time for occurrence of the first swollen package and number of toxic swells were recorded over 110 days of incubation at 27 C. The above variables were compared to bacon containing 80 and 120 ppm NaNO2 as well as a commercial sample. Presence of potassium sorbate in the cure significantly reduced the number of toxic swollen packages occurring during incubation and lengthened the time before a toxic swollen package was observed. The presence or absence of 40 ppm NaNO2 appeared to have no significant effect on the sorbate inhibition of C. botulinum in bacon in this study. Microbial growth of uninoculated samples was also retarded by addition of potassium sorbate to the brine. Flavor panel evaluations indicated that potassium sorbate decreased preference slightly using experienced judges. Also, reduced occurrence of nitrosopyrrolidine with reduced nitrite was observed.

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The effect of antioxidants, reducing agents, and a chelating agent were tested in perishable canned cured meat. Isoascorbate, ascorbate, and cysteine enhance the antibotulinal effect of nitrite in perishable canned cured meat. It was determined that this effect was not due to the antioxidant or reducing properties which these compounds possess. The data indicate that they enhance the effect of nitrite by sequestering a metal ion(s) in the meat. It is suggested that nitrite (nitric oxide) reacts with a cation dependent material within the germinated botulinal cell and blocks a metabolic step which is essential for outgrowth. Enhancement of nitrite by isoascorbate, and similar compounds, may be due to preventing repair of damaged material or formation of new cation dependent material.