Synergistic Inactivation of Listeria monocytogenes on Chicken Breast by Combined Pulsed Light and Peracetic Acid

Listeria monocytogenes is a major concern in the poultry industry due to its ability to form biofilms on processing surfaces, increasing resistance to sanitation, and enabling persistence and cross-contamination. This study evaluated the efficacy of combining non-thermal treatments, pulsed light (PL) and peracetic acid (PAA), for L. monocytogenes inactivation on chicken breast. The effects of PL fluence (6.2, 12.2, and 14.1 J/cm²), energy delivery mode (6 × 420 µs or 12 × 210 µs), acid type (PAA or HCl), and immersion solution pH (3.15 and 3.05) were investigated. Treatment interactions were assessed using a synergism index ( S ), and post-treatment behavior was evaluated by modeling growth kinetics at 7°C using the Baranyi and Roberts model. The combination of PL + PAA was significantly more effective ( p < 0.05) than individual treatments or PL + HCl. Maximum inactivation (2.07 Log CFU/cm²) was achieved at 14.1 J/cm² delivered in 12 × 210 µs pulses combined with PAA at pH 3.05. Shorter, more frequent pulses resulted in higher lethality, likely due to increased peak irradiance. The combined treatment extended the lag phase by approximately 111% (from 18 to 38 h) and reduced the maximum cell concentration density compared with the control. Overall, PL + PAA showed a clear synergistic effect, providing both immediate microbial reduction and delayed regrowth. These findings support the application of this combined treatment as a non-thermal strategy to control L. monocytogenes in poultry processing environments, improving product safety and reducing contamination risks.