Inactivation of Pseudomonas stutzeri in Beef Using High Pressure Processing, Gamma Radiation, and Ultraviolet Light

Introduction: Recent advances in microbiome research indicate that abnormal gut microflora may play a role in human disease processes. Pseudomonas species are typically regarded as nuisance spoilage microorganisms in foods, including beef. However, recent research on food and human gut microbiomes has indicated that P. stutzeri, may play a role in creation of abnormal gut microflora and inflammatory bowel disease in people with Autism Spectrum Disorder.

Purpose: The purpose of this study was to determine the inactivation kinetics of P. stutzeri in beef using High Pressure Processing (HPP), Gamma Radiation (GR) and Ultraviolet Light (UV-C).  

Methods: A six-isolate cocktail of P. stutzeri was inoculated (10⁹ CFU/g) into irradiated beef which was then treated with the non-thermal process interventions, and the P. stutzeri recovered using APC Petrifilms.

Results: When the P. stutzeri was inoculated into 80% lean ground beef and subjected to HPP (450 mPa, 0 - 15 min, 5°C) the D-10 was 2.09 min. When the P. stutzeri cocktail was suspended in the ground beef and irradiated (0-1.0 kGy, 5°C) the D-10 was 0.20 kGy. Approximately 1.6 log of P. stutzeri was inactivated on beef surfaces subjected to UV-C (5 mW/cm², 0-2.0 J/cm², 5°C).  When the ability of UV-C to inactivate the P. stutzeri suspended in beef purge inoculated onto food grade high density polyethylene and stainless steel surfaces was examined, ca. 3.5 log (0.5 J/cm²) and 6.5 log (1.0 J/cm²) reductions were observed.

Significance: These results indicate that HPP, GR, and UV-C, which do not require the use of exogenous water or chemicals to inactivate microorganisms, can be used to control P. stutzeri in beef and beef purge. While still speculative, control of opportunistic pathogens such as P. stutzeri may yield benefits for people with certain genetic or metabolic conditions.