Spoilage Pseudomonas survive common thermal processing schedules and grow in emulsified meat during extended vacuum storage

Some Pseudomonas species are common meat spoilage bacteria that are often associated with the spoilage of fresh meat. The recently reported ability of these bacteria to also spoil cooked and vacuum packaged meat products has created the need to investigate all potential routes of spoilage they may be able to utilize. The objective of this experiment was to determine if spoilage Pseudomonas spp. survive thermal processing and grow during refrigerated storage under vacuum. Pseudomonas spp. isolates collected from spoiled turkey products were inoculated into a salted and seasoned meat emulsion that was vacuum sealed and thermally treated to final temperatures of 54.4 and 71.1 degrees C to mimic thermal processes commonly used in the meat industry. Samples were stored for a total of 294 days at 4 and 10 degrees C and plated using Pseudomonas spp. specific agar plates. Pseudomonas spp. concentrations were below the detection limit (0.18 log(10) CFU/g) immediately after thermal processing and were first recovered from thermally processed samples after 14 days of storage. The final concentration was greater than 2 log(10) CFU/g (p < 0.05 compared to post-thermal processing) in thermally processed treatment groups at the end of storage, indicating that these Pseudomonas spp. isolates were able to survive thermal processing and grow during extended vacuum storage. This raises concerns about the ability of spoilage bacteria to survive the thermal processing schedules commonly used in the meat industry and confirms that some Pseudomonas spp. are capable of thriving in products other than aerobically stored fresh meat.