Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2023
Publication Date: 1/18/2023
Citation: Bermudez-Aguirre, L.D., Niemira, B.A. 2023. Microbial inactivation models of Salmonella Typhimurium in radio frequency treated eggs. Food Control. https://doi.org/10.1016/j.foodcont.2023.109634.
Interpretive Summary: Radio frequency (RF) has been used to pasteurize eggs in short time. Previous results showed the effective inactivation of Salmonella Typhimurium 53647 inoculated in eggs after 20 minutes of treatment. Mathematical models were fitted to the microbial inactivation curves to facilitate the improvement of the RF process for in-shell egg pasteurization. Six mathematical models were adjusted to the survivor’s curves (linear, Weibull, logistic distribution, Fermi distribution, extreme tailing, and flat-shoulder equation). Six treatments were analyzed: hot air, hot water immersion, and hot water spraying, with and without radio frequency. The treatments varied in efficacy, based on the energy applied. For most datasets, the Weibull model gave the best mathematical fit. The model parameters clearly described 1) the effect of radio frequency in microbial inactivation, and 2) the effect of bacteria population dynamics on the efficacy of the process. Based on these results, the most effective treatment for in-shell egg pasteurization is RF together with hot water spray. These models will be useful in scaling up the RF process for commercial pastuerization of shell eggs.
Technical Abstract: The inactivation of Salmonella Typhimurium 53647 was previously conducted using selected radio frequency processes in in-shell eggs. The combination of hot air (HA), hot water immersion (HW), and hot water spray (HWS) were evaluated alone (56.7°C) and in combination with radio frequency (40.68 MHz, 35 W, 4.5 min). Microbial inactivation did not follow first-order kinetics in any treatments. Alternative mathematical approaches were used to describe the inactivation of S. Typhimurium in eggs. These models were based on the Weibull distribution, the logistic distribution, the Fermi distribution, a model for extreme tailing, and a model for flat shoulder with log-linear continuation. The survival curve from the treatment HWS plus radio frequency showed the best fit for the Weibull (R2 0.9900) and the Fermi distribution (R2 0.9999), and the extreme tailing model (R2 0.9749). This information is currently used to optimize the radio frequency pasteurization of eggs.