Inactivation Kinetics of Listeria monocytogenes Applying Mild Temperatures and Fractionated Mexican Oregano Essential Oil (Poliomintha longiflora Gray) in a Modified Simulated Meat Medium

Meat products are highly susceptible to contamination with Listeria monocytogenes, a foodborne pathogen associated with high mortality. To mitigate this risk, this study explored the use of Poliomintha longiflora oregano essential oil, both in its pure (PEO) and fractionated (FIV, fraction IV obtained at 140 °C) forms, as part of a hurdle technology combining natural antimicrobials with mild thermal treatments. In vitro thermal inactivation experiments were conducted at 52, 54, 57.5, and 63 °C using a simulated meat medium. The FIV group, characterized by 60.23% carvacrol and 21.17% thymol, exhibited significantly enhanced bactericidal activity, achieving up to 5.5 log-reductions in L. monocytogenes at 57.5 °C within 3 min, compared to <2 log-reductions for the control group. Inactivation kinetics were well described by the Weibull–Mafart model. The δ-values, defined as the time required to achieve a 1-log reduction in bacterial population, were consistently lower for FIV compared to the control across all tested temperatures (e.g., δ52°C = 0.64 min vs. 8.47 min for control). The estimated z-values, which represent the temperature increase required to achieve a tenfold change in δ-value, were 5.75 °C (control), 5.20 °C (PEO), and 5.00 °C (FIV), suggesting a consistent thermal sensitivity but enhanced inactivation efficacy with the essential oils. These findings suggest that fractionated oregano essential oil is a promising hurdle to shorten thermal treatments in meat products, thereby lowering L. monocytogenes contamination risk while preserving product quality.