Pasteurization of eggs in the shell

Application of Ultrasound to Animal-Based Food to Improve Microbial Safety and Processing Efficiency

Animal-based foods such as meat, dairy, and eggs contain abundant essential proteins, vitamins, and minerals that are crucial for human nutrition. Therefore, there is a worldwide growing demand for animal-based products. Since animal-based foods are vital resources of nutrients, it is essential to ensure their microbial safety which may not be ensured by traditional food preservation methods. Although thermal food preservation methods ensure microbial inactivation, they may degrade the nutritional value, physicochemical properties, and sensory qualities of food. Consequently, non-thermal, ultrasound food preservation methods are used in the food industry to evaluate food products and ensure their safety. Ultrasound is the sound waves beyond the human audible range, with frequencies greater than 20 kHz. Two types of ultrasounds can be used for food processing: low-frequency, high-intensity (20-100 kHz, 10-1,000 W/cm2) and high-frequency, low-intensity (>1 MHz, <1 W/cm2). This review emphasizes the application of ultrasound to improve the microbial safety of animal-based foods. It further discusses the ultrasound generation mechanism, ultrasound technique for microbial inactivation, and application of ultrasound in various processing operations, namely thawing, extraction, and emulsification.

A review on egg pasteurization and disinfection: Traditional and novel processing technologies

Salmonella Enteritidis is a pathogen related to many foodborne outbreaks involving eggs and egg products. Regulations about whether eggs should be pasteurized are very different and inconsistent worldwide. In the United States, eggs are not required to be pasteurized. Hence, less than 3% of the eggs in the country are pasteurized. The standard pasteurization method (57°C, 57.5 min) uses a long thermal process that increases the cost of the product and affects its quality. Foodborne outbreaks can be reduced if eggs are properly pasteurized to inactivate Salmonella spp. However, the technology to pasteurize eggs needs to offer a faster and more reliable method that can be scaled up to industry settings at a low cost and without affecting product quality. Several novel technologies have been tested for eggshell disinfection and egg pasteurization. Some thermal technologies have been evaluated for the pasteurization of eggs. Microwave has limited penetration depth and is a technical challenge for egg pasteurization. However, radio frequency can penetrate eggshells effectively to inactivate Salmonella, considerably reduce processing time, and maintain the quality of the product. Nonthermal technologies such as ultraviolet, pulsed light, cold plasma, ozone, pressure carbon dioxide, electrolyzed water, and natural antimicrobials have been explored for surface cleaning of the intact egg as alternatives without affecting the internal quality. This review presents some of these novel technologies and the current challenges. It discusses the possible combination of factors to achieve the egg's internal pasteurization and the eggshell's disinfection without affecting the quality at a low cost for the consumer.

A Successful Technique for the Surface Decontamination of Salmonella enterica Serovar Typhimurium Externally Contaminated Whole Shell Eggs Using Common Commercial Kitchen Equipment

Eggs are a highly nutritious food source used in a wide range of food products. In Australia, eggs are a frequent source of foodborne salmonellosis outbreaks, associated with eggshell contamination with Salmonella enterica serovar Typhimurium (ST). Despite their potentially hazardous nature, raw eggs are often used and consumed in mayonnaise, mousse, ice cream and eggnog. The aim of this study was to develop a shell egg decontamination method that removed ST contamination from the outside of an egg without impacting its usability. The decontamination method was developed by the adaptation of a temperature-controlled water bath (commonly present in kitchens and associated with the sous-vide technique) for the surface decontamination of eggs. The outside of whole eggs was artificially inoculated with two ST strains. The eggs were decontaminated by placing in a sous-vide cooker with the water heated to 57°C. The remaining viable ST present on the whole shell egg, crushed shells, internal egg contents and sous-vide water were enumerated over time by culturing onto XLD agar. The quality of the uncontaminated heat-treated eggs was determined by measuring the Haugh unit, yolk index, albumen pH, thermocoagulation, and stability of foam. A blind control study was conducted to assess the acceptability and usability of the treated eggs by chefs and food handlers for the preparation of mayonnaise. Complete decontamination of ST was achieved by treating eggs for 9 min in the sous-vide cooker (57°C). No statistically significant difference was observed in the quality of treated eggs compared with nontreated eggs using the quality measurements and acceptability score from chefs. This method provides a simple approach that can be adopted by chefs and food handlers to obtain safe eggs before the preparation of raw egg products.

Egg Safety in the Realm of Preharvest Food Safety

Eggs are nutritious, yet they are a highly perishable commodity like other protein sources such as meat. Even though steps are taken all along the production process of shell eggs, from farm to table, the potential for contamination of the shells and egg contents poses a high risk to consumers. The main sources of contamination can be categorized as vertical transmission, in which the layers can be carriers of pathogens and can pass them on during egg formation, and horizontal transmission, in which environmental factors such as water, feed, layer houses, and personnel are the main source of contamination. Ongoing preharvest practices might not be enough to completely eliminate pathogens from shell eggs; however, consistently following good practices along with proper handling during transportation and retail sale and by consumers can be significant in reducing the risk. This article discusses the various aspects of production practices, their potential for cross-contamination, and decontamination technologies for shell eggs.

Salmonella enteritidis in shell eggs: evolving concerns and innovative control measures

The issue of egg contamination with Salmonella enterica serovar Enteritidis rose to prominence several decades ago with increasing rate of infection around the world. Recent outbreaks have assured that this problem maintains a place in the public consciousness. Extensive research has been conducted to investigate the factors precipitating contamination events, their avoidance, and mitigation of the threat of contaminated eggs; consequently, regulations have been put in place to increase the safety of shell eggs. Despite these measures, rate of illness remains significantly higher than projected goals. This chapter includes information regarding the contraction of Salmonella species by laying hens and the subsequent deposition of these cells in shell eggs. Particular attention will be given to the prevalence of Salmonella Enteritidis in eggs and egg-containing products relative to other salmonellae. Research has been conducted to elucidate the mechanisms behind the fitness of Salmonella Enteritidis strains for this environment, but a consensus has yet to be reached. Novel methods of sanitizing shell eggs also are reviewed.

Optimizing irradiation treatment of shell eggs using simulation

Accurate dose calculation is needed to ensure proper irradiation process control to maintain the freshness of the product. Our objective was to establish the best irradiation treatment for shell eggs taking into account their different components (shell, albumen, yolk). Computer tomography (CT) data were used to generate a 3-D geometry to simulate dose distributions within 1 egg using a radiation transport code (MCNP5). Radiation energies used for simulation were 10 MeV (high-energy) and 1.35 MeV (low-energy) for electron beam, 5 MeV for X-rays, and 1.25 MeV for a gamma-rays source such as Co-60. Low-energy (surface) e-beam simulation indicated that electrons only penetrate up to the thin albumen (0.6 cm). Because of their irregular shape, shell eggs should be irradiated from the side (rather than from top or bottom) for better dose distribution. For high-energy e-beam simulation, the entire egg was irradiated and the best results were obtained when the egg was irradiated from both sides, showing a dose uniformity ratio (D(max)/D(min)) of 1.42. X- or gamma-ray source simulation from one side only, the dose uniformity ratio was 3.38 and 3.12, respectively. For surface-only irradiation, a low-energy e-beam provides a uniform dose distribution. To irradiate the entire egg, 2-sided high-energy e-beam sources are required for an efficient treatment. Unless the product rotates in front of the source, the dose uniformity ratio for X-ray or gamma ray is not adequate for shell egg treatment for pathogen decontamination purposes. Practical Application: Proper control of irradiation treatment of foods such as shell eggs is critical to ensure pathogen inactivation while maintaining product freshness. Simulation allows for accurate calculation of dose distribution within the egg to further establish the best irradiation scheme.

Effect of pasteurization of shell egg on its quality characteristics under ambient storage

Three thermal processes viz. dry (55°C, 2 h), moist (57°C, 5 min) and microwave (power 9, 20 sec) were studied to determine their efficacy for the pasteurization of intact chicken eggs based on the extent of inactivation of artificially inoculated Salmonella typhimurium (ST) in the yolk of shell eggs and alteration in albumen protein solubility (APS). Moist heat treatment was superior to others as it brought about 2 log cfu/ml reduction of inoculated ST in much less time than dry heating but changes in APS were not significant. Subsequent quality evaluation of normal (uninoculated) eggs subjected to moist heat pasteurization during 15 days of ambient (35°C, 36% RH) (35 ± 0.5°C, 36 ± 2% RH)storage revealed no significant effect on percent loss in egg weight, albumen pH, viscosity of albumen and yolk and thiobarbituric acid values between pasteurized and unpasteurized eggs. Pasteurization had no adverse effect on foam volume and foam stability of albumen during storage in comparison to those of raw eggs. Naturally occurring aerobic mesophilic bacteria, coliforms, staphylococci, yeast and moulds on the egg shell surface and in egg contents got markedly reduced by pasteurization of shell eggs and their multiplication also retarded during storage. Both pasteurized and raw eggs remained fairly acceptable sensorily up to 10 days of storage at ambient conditions.

Computational fluid dynamics analysis for process impact assessment during thermal pasteurization of intact eggs

Transient temperature and albumen velocity profiles during thermal pasteurization of intact eggs were studied using a commercial computational fluid dynamics (CFD) package. Simulated temperature profiles were in close agreement with experimental data for eggs of different sizes. Convective heat transfer only occurred in the egg white fraction, and conductive heat transfer only occurred in the yolk. For process assessment, a generally accepted kinetic inactivation model for Salmonella Enteritidis was incorporated into the CFD analysis. Minimum process times and temperatures needed to provide equivalent pasteurization at 5-log reductions of the target microorganism were obtained on a theoretical basis. The combination of CFD analysis and inactivation kinetics can be very useful for assessing pasteurization of intact eggs and can enable processors to gain a better understanding of these processes and to establish process conditions for consumer-safe eggs.

Thermal inactivation kinetics of Salmonella spp. within intact eggs heated using humidity-controlled air

The heat resistance of six strains of Salmonella (including Enteritidis, Heidelberg, and Typhimurium) in liquid whole egg and shell eggs was determined. Decimal reduction times (D-values) of each of the six strains were determined in liquid whole egg heated at 56.7 degrees C within glass capillary tubes immersed in a water bath. D-values ranged from 3.05 to 4.09 min, and significant differences were observed between the strains tested (alpha = 0.05). In addition, approximately 7 log10 CFU/g of a six-strain cocktail was inoculated into the geometric center of raw shell eggs and the eggs heated at 57.2 degrees C using convection currents of humidity-controlled air. D-values of the pooled salmonellae ranged from 5.49 to 6.12 min within the center of intact shell eggs. A heating period of 70 min or more resulted in no surviving salmonellae being detected (i.e., an 8.7-log reduction per egg).

The effect of shell egg pasteurization on the protein quality of albumen

The effect of a low-temperature, extended-time, in-shell pasteurization process on the protein quality of egg albumen was evaluated. Ten dozen fresh chicken eggs were pasteurized in a hot-air oven at 55 C for 180 min. The eggs were refrigerated and broken out for analysis on Days 0, 7, 14, 28, 42, and 56 following pasteurization. There were no significant differences in total or soluble protein over the experimental period for the pasteurized or unpasteurized albumen. Mean protein content was 80.6 +/- 0.5% for the pasteurized albumen and 80.9 +/- 0.5% for the unpasteurized albumen. In vitro digestibility, as measured by the AOAC method, was 82.4 +/- 0.7% for the pasteurized albumen and 81.7 +/- 0.6% for the unpasteurized albumen. There were no significant differences over the experimental period in the digestibility of the samples. Free amino acids and discriminant-computed protein efficiency ratio (DC-PER) also did not differ between the pasteurized and unpasteurized albumens or over the experimental period. The in-shell pasteurization process used had no effect on the protein quality of albumen.

Review of studies on the thermal resistance of Salmonellae

Heat resistance data for different serotypes of Salmonella enterica in different food products and laboratory media are reviewed. From all D-values reported, the highest heat resistance of Salmonella was in liquid eggs and liquid egg yolks. The equation from a line drawn through the highest D-values, and above all values reported, was log D-value = 11.7 - 0.188T degrees C. From this equation, the calculated z-value was 5.3 degrees C (9.5 degrees F), and a process at 71degrees C (160 degrees F) will require 1.2 s to inactivate 1 log of Salmonella cells. This calculation did not include data that evaluated the heat resistance after stress conditions or data for Salmonella Senftenberg. The heat resistance of Salmonella is highly influenced by the strain tested, the type of experiment (log reduction versus end-point), culture conditions prior to the experiment, heating menstruum, and recovery conditions. Heat resistance data for Salmonella are still nonexistent or scarce in chicken meat, fruit juices, and aquacultured fish.

The incredibly functional egg

A review of some of the old and newer uses of eggs. Twenty-one functional uses of eggs are described. The changing attitudes of the American population relative to eggs first with respect to cholesterol and recently with regards to potential pathogens in eggs are briefly discussed. The newer uses of eggs as nutraceuticals and sources for pharmaceuticals are emphasized. The outlook for eggs in the human diet remains good.