Effect of Heat Treatment and Selected Antimicrobials on the Shelf‐life and Safety of Cooked, Vacuum‐Packaged, Refrigerated Pork Chops

Abstract

The shelf-life of refrigerated (24°C) pork chops inoculated with Clostridium sporogenes PA3679 and Staphylococcus aureus 288 was examined in products sliced from loins cooked to 66°C (150"F), dipped in 5% polyphosphate blend, 2.5% potassium sorbate or 2% acetic acid solutions, vacuum-packaged and stored at 2-C. The effect of a second in-the-bag cooking step to 66°C (150°F) after vacuum packaging was also studied. Pork chops not reheated after packaging showed incipient spoilage after 15 days at 2-&C, depending on surface treatment. The second cooking increased the shelf-life of refrigerated product to more than 60 days and reduced counts of inoculated cultures to undetectable levels. However, on exposure of the chops to simulated mishandling (24-25"C), clostridial growth was detected in all samples except those dipped in polyphosphate or acetic acid solutions.

Microbiological Safety of Cooked Beef Roasts Treated with Lactate, Monolaurin or Gluconate

“…The inoculation was done using a sterile insulin syringe and a 21gl needle (Plastipak", Becton, Dickinson & Co., Rutherford, NJ) in the approximate geometric center of the roast section. The closhidial spore suspension (10) spores/ml) was prepared according to the procedure outlined by Swank (1972) by using a strain of C. sporogenes that had been selected for rhizoid colony formation to facilitate differentiation from other bacteria during plate counting as described by Molins et al (1986). The Listeria inoculum (lo3 cells/ml) was prepared by diluting with 0.1% sterile peptone water an appropriate volume of a culture grown at 37°C for 24 hr in Brain Heart Infusion broth (BHI, Difco).…”

“…Clostridium sporogenes was enumerated in the same plates prepared for total anaerobic and facultative anaerobic bacterial counts. This was possible by the unique rhjzoid morphology of the PA 3679 culture used as inoculum (Molins et al, 1986). Viable anaerobic spore counts were obtained by heat shocking 10 mL of initial homogenate (80°C for 20 mins), plating serial dilutions with TSA containing 1% starch, and incubating the plates anaerobically (3O"C, 48 hr).…”

“…Lack of competition by other spoilage bacteria would make it likely that such roasts would not have been considered spoiled by consumers. Siminovic et al (1985), Lechowich (1988), and Prabhu et al (1988) warned about the botulinal hazards inherent to seemingly wholesome cooked muscle foods for which spoilage flora had been mostly destroyed. Our results confirmed the instability of refrigerated, cooked, nitrite-free, "microwave-ready" meat products and should be viewed with concern by the meat industry and regulatory agencies.…”

“…Cooked, vacuum-packaged, refrigerated meat products may also present a listeriosis hazard (Schwartz et al, 1988). Substerilizing cooking temperatures (Harrison and Carpenter, 1989), partial elimination of competing spoilage organisms (Harris et al, 1989) and long shelf-life at low, above-freezing temperatures typify conditions that may lead to growth and predominance of Listeria monocytogenes.…”