# Analysis of Shell Egg Pasteurization Using Computational Fluid Dynamics
###### Abstract  
In the present work, the thermal pasteurization process of shell eggs was studied through Computational Fluid Dynamics. For large-size eggs (63-72 g), the required heating times at several different heating medium (water) temperatures, namely 54, 56, 58, and 60 \({}^{\circ}\)C (followed by cooling in water at 20 \({}^{\circ}\)C), were estimated as 55.1, 37.2, 29.1, and 24.5 min. Calculations were based on a 5-log reduction of the _Salmonella enteritidis_ population, that is, for a target \(F\) value at 60 \({}^{\circ}\)C in 0.85 min. Computations were performed at the critical point of the egg, which was established from \(F\) value distribution determinations and was approximately located at the center of the yolk. Both heating and cooling cycle lethality was considered. Similar calculations were performed for medium (53-62 g) and extra-large-size eggs (>72 g). Microbial destruction occurring during the cooling cycle of the pasteurization process was greater for higher heating temperatures and larger egg sizes, ranging between 11.8% of the total destruction for the medium eggs heated at 54 \({}^{\circ}\)C and 72.9% for the extra-large eggs at a heating medium temperature of 60 \({}^{\circ}\)C. Therefore, destruction during the cooling cycle should not be ignored during the design of thermal pasteurization processes. For the kinetic parameters employed, quality degradation calculations revealed minimal changes for the processes investigated. thermal processing; \(F\) value; critical point; _Salmonella enteritidis_; CFD 202  
thermal processing of eggs [2]. In the industry, the pasteurization process is applied to about only 1% of the eggs available in the market, and therefore eggs should be properly cooked by the consumer before consumption [5]. It is estimated that 1 in every 20,000 eggs produced in the United States is _Salmonella_-positive (0.005%) [6], while in Europe the frequency is higher at 0.37% [7]. Outbreaks due to _Salmonella_ spp. are still a big issue for the food industry, with the latest outbreaks [8; 9] impacting several countries and consumers, making whole egg pasteurization a necessary hazard step barrier. Implementing thermal pasteurization remains the principal industrial method to ensure the safety of eggs and egg products [5]. _Salmonella enterica_ is the egg's most heat-resistant pathogen (\(D_{60^{\circ}\mathrm{C}}=0.17\) min, \(z\) value = 4.08 \({}^{\circ}\mathrm{C}\)) [10; 11]. The standard pasteurization method at 57 \({}^{\circ}\mathrm{C}\) for 57.5 min might unnecessarily increase costs and affect product quality due to long heating time of the thermal process [12]. The pasteurization process makes the egg safer for the consumer; however, optimization of the process is necessary to ensure food safety without significant quality degradation. For many years, microbial destruction of _Salmonella enterica_ has been extensively studied experimentally [5; 12; 13; 14]; yet only recently, with the development and accessibility of computer simulation programs, has an increase in studies regarding optimizing the pasteurization process by studying and improving heat and mass transfer modeling been seen [11; 15; 16]. These studies, using Computational Fluid Dynamics (CFD), were able to simulate the temperature profile within whole eggs and calculate the time required to achieve the target lethality for _Salmonella enterica_. At this point, it is worth mentioning that CFD is a transformative tool in food processing, offering precision in modeling heat transfer, fluid dynamics, and mass transfer. It enables optimization of thermal processes like pasteurization and sterilization, enhancing food safety and quality while reducing energy use and experimental costs [17; 18]. Using CFD simulation, studies on egg pasteurization were able to determine the slowest heating point (or zone) within the egg and design the process based on this as the worst-case scenario for food safety [11; 15; 16].