Thermal resistance of avirulent Salmonella enterica serovar Typhimurium in albumen, yolk, and liquid whole egg.

Authors: Bermudez-Aguirre, Luz; Boyd, Glenn; Niemira, Brendan; Uknalis, Joseph

Submitted to: ACS Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2024
Publication Date: 8/14/2024
Citation: Bermudez-Aguirre, L.D., Boyd, G., Niemira, B.A., Uknalis, J. 2024. Thermal resistance of avirulent Salmonella enterica serovar Typhimurium in albumen, yolk, and liquid whole egg. ACS Food Science and Technology. https://doi.org/10.1021/acsfoodscitech.4c00108.
DOI: https://doi.org/10.1021/acsfoodscitech.4c00108

Interpretive Summary: The use of surrogate microorganisms is required where pathogens are not allowed because of a safety risk, for example, during process validation in pilot plant or industry settings. However, the available microbial strains of surrogates are limited for some species, and their resistance to different inactivation factors and specific food matrices needs to be assessed and compared to the pathogenic strain before using them. Therefore, the thermal resistance of a surrogate strain of Salmonella was tested in broth and liquid whole egg at different temperatures, from 50°C to 60°C. Mathematical models were used to evaluate the thermal resistance using two parameters, the decimal reduction time, known as D-value, and the decimal reduction temperature, known as the z-value. These values were used to calculate the pasteurization standard for this surrogate microorganism in liquid whole egg. The results showed the thermal resistance of this microorganism very similar to the pathogenic strain in terms of D- and z- values, but also in the required time to achieve the pasteurization when compared to the official standard.

Technical Abstract: The thermal resistance of avirulent strain of Salmonella enterica serovar Typhimurium inoculated in broth and liquid whole egg (LWE) was evaluated at different temperatures. A log-linear and a Weibullian model were used to calculate D- and z-values. Experiments included assessing and overseeing the come-up time (CUT) to reach the desired temperature. Results showed a higher reduction time for LWE compared to broth (D60°C =0.73 ± 0.03 min vs. D60°C = 0.43 ± 0.05 min). The effect of CUT was only significantly different (p < 0.05) for the D-values at 60°C. Statistical analysis showed that the Weibull model best fit the survival data according to R2 and RSME. The bias factor (Bf) indicated no under- or over-prediction from the Weibull model, and the fitting could be classified as good. The required 5D pasteurization standard for this avirulent Salmonella strain at 60°C was 3.3 ± 0.3 min (log-linear) and 3.6 ± 0.2 min (Weibull). The heat resistance of this Salmonella strain is very similar to the pathogenic strain and can be used for process validation without safety risks.