Salmonella Risk Assessment Toolkit

This section identifies possible risks associated with egg product manufacturing processes including transport, storage, sale, management, use and maintenance of facilities & equipment in egg production.

Facility

Inappropriate building / facility design

All buildings and facilities used in egg production should comply with Food Standards Australia New Zealand (FSANZ) requirements. These aim to ensure egg products are safe and suitable to eat, with a strong emphasis on human health and hygiene.

The FSANZ standards include provisions that premises, fixtures, fittings, equipment and transport vehicles can be adequately cleaned and sanitised. This will minimise potential for bacterial contamination during post-grading egg processes.

Facilities that produce raw and low-cooked egg products should particularly have regular cleaning and sanitisation procedures in place. There may be a need for designated ‘clean’ and ‘dirty’ areas for food preparation.

It should be noted cleaning involves removing general dirt, grease and food waste and should be done before sanitising, which destroys micro-organisms.

hand sanitising facilities and protective clothing should be used in pasteurisation areas
Egg should be rapidly reheated in air forced ovens, microwaves or similar

Preparation of raw and low-cooked eggs products

Production of raw and low-cooked egg products needs careful attention. Many food-borne illness outbreaks in Australia have been caused by operators using the wrong egg handling procedures or recommended temperatures during preparation or cooking.

Controlling Salmonella in a kitchen environment is complex. For example, if bacteria are present in foods with low water activity such as chocolate or peanut butter, it takes a longer period of temperature treatment to destroy the bacteria than in food with high water content, such as raw egg mix. This can be as much as one year at ambient temperatures. Sugar can increase the heat resistance of Salmonella by reducing the water activity of the food.

Acidity is another factor and experience indicates it can take longer to destroy Salmonella at pH5.5 than at pH8.

Several outbreaks of Salmonella have been linked to highly acidified products, including apple cider and orange juice. If operators are using pH to control bacteria growth, research has found acidified products may need to be kept for several days at ambient temperatures before refrigeration to achieve a Salmonella-free status. 

When preparing eggs, several other variables can also affect the destruction rate and resistance of Salmonella, including:

  • rate of change of environmental conditions
  • amount of Salmonella present
  • cooking time
  • cooking temperature

Appropriate processing and handling practices need to be identified and conveyed to staff who are preparing, handling or serving food. This is especially important for raw or low-cooked egg food products. Without stringent systems, any food-borne illness outbreak in a retail business can be devastating.

Low cooked or raw egg food production needs careful attention
Raw egg food products are a higher risk

Raw or low-cooked egg products / foods served to vulnerable population

Raw and low-cooked egg products shouldn’t be served to ‘vulnerable populations’, unless Food Standards Australia New Zealand (FSANZ) measures have been met.

Vulnerable populations include people living in care facilities, such as hospitals, aged homes, hospices and childcare centres, or those having meals delivered.

Raw egg product can pose a higher risk to these groups if the egg internal contents has been contaminated and consumed. Any bacteria on the eggshell can also transfer into food during egg cracking or separation.

Vulnerable populations are more susceptible to food-borne illnesses and can succumb to illness from a lower dose of bacteria than the general population.

Extra care should be taken when serving low cooked eggs to vulnerable populations

Cross contamination of utensils, equipment or surfaces in contact with eggs

Regular cleaning and sanitising is needed for all utensils, equipment and surfaces that contact egg internal contents or eggshells prior to coming into contact with other food.

Any bacteria on the eggshell can be transferred to the surface it contacts, posing a risk of cross-contaminating food that also has contact with that surface.

Bacteria and viruses are able to grow inside the egg and in raw egg products, so this type of cross-contamination must be avoided.

Kitchen towels and sponges used to clean or dry utensils, surfaces, equipment and staff hands can harbour Salmonella for prolonged periods and be a source of contamination of raw egg products.

Studies have found some common disinfectants used to remove Salmonella in post-grading and food preparation facilities are not always effective, especially when Salmonella is able to form a biofilm – or bacterial protective ‘coat’ – in unfavourable conditions.

It is recommended food containing raw egg product should be prepared using methods that prevent cross-contamination and be consumed within two hours if stored at ambient temperatures.

Research investigating Salmonella Enteritidis demonstrated that both dry and wet contaminated egg droplets were able to cross-contaminate other foods and surfaces. 

The invasive capacity of Salmonella is highly dependent on the environment.

In a food service environment, there are typically many sources of bacteria enrichment, including the presence of salt and sugars. This poses a higher human health risk than Salmonella present in an environment with limited enrichment.

The longer an egg product contaminated with Salmonella is kept at ambient temperatures, the higher the risk of illness. This is due to increased bacterial load and potentially increased invasive capacity to egg internal contents. 

Using eggshells to separate eggs is not recommended, particularly for the preparation of raw or low-cooked egg products

Food preparation equipment with multiple components is at high risk of cross-contamination due to the difficulty in achieving appropriate cleaning. If using stick mixers or blenders, it is advised these are taken apart for thorough cleaning. The risk is water entering components during washing and, if not cleaned thoroughly, can lead to potential bacteria proliferation and contamination of foods it is then used to prepare.

Australia has had several incidences of food-borne illness outbreaks with the probable bacteria source being Salmonella contaminated stick mixers and blenders. 

Using eggshells to separate eggs is not recommended
All utensils need to be thoroughly cleaned
Blending sticks and intricate equipment are notoriously high risk
Sponges and towels used to wipe down surfaces can harbour salmonella

Staff knowledge and training

Staff food safety training

Training and protocols are needed to minimise the spread of bacterial contaminants by staff, contractors, visitors, family members and other personnel during egg processing and food preparation. A detailed log of visitor entry and information should be maintained.

It is recommended all staff receive detailed information about preparing, handling and serving high-risk foods, such as raw or low-cooked egg products, and implement appropriate practices to minimise contamination risks.

Human error or mishandling of food account for a big proportion of Salmonella food-borne illness outbreaks linked to the consumption of egg products.

Resources

Staff training and protocols are essential to minimise contamination risks
Signage and training is important for staff awareness

Personal health hygiene and behaviour

Staff, contractors, family members and other personnel who are sick should not handle or prepare eggs, raw egg products or foods containing low-cooked eggs until at least 48 hours after recovering from symptoms.

Good personal hygiene and behaviour practices are required when handling whole eggs and egg internal contents, including:

  • no coughing or sneezing
  • avoiding all contact if suffering gastrointestinal upsets
  • regular hand washing.

Human pathogens, including Salmonella, that are present on the body or spread on to eggshells during handling can infect other humans and contaminate surfaces, eggs or egg internal contents. This cycle can persist if humans are then re-infected from these sources.

Egg internal contents provide excellent growing conditions for many bacteria, viruses and fungi.

Research indicates both symptomatic and non-symptomatic food handlers have caused food-borne illness outbreaks.

Salmonella-infected food handlers should be excluded from work until at least 48 hours after symptoms have ceased.

Humans can still carry Salmonella for weeks or months after infection. The Australian Government Department of Health has produced a set of guidelines for managing food handlers during Salmonella outbreaks.

Staff should practice regular hand washing when preparing eggs
High personal hygiene standards need to be followed when handling raw egg products

Insect / rodents / animals

Robust biosecurity measures during processing, handling and serving egg products include ensuring minimal insect, rodent and animal access to storage and transport areas.

It is recommended an adequate and regularly monitored rodent control program is implemented and baits replaced a regularly.

Insects such as flies, beetles and cockroaches and rodents, including pets, pose a high risk of disease contamination.

Livestock, domestic pets, chickens, turkeys, wild birds, ducks, foxes and other wild animals naturally carry various types of Salmonella that can spread. These can contaminate storage areas and transport equipment, which can then cross-contaminate eggs.

Rodent bait stations like this can be used
Pests can carry Salmonella, and should be controlled

Transport of egg products

Raw egg pulp transport

It is recommended to transport eggs or raw egg pulp in regularly cleaned, fit-for-purpose vehicles, with appropriate equipment and at temperatures of less than 5°C if chilled and below -18°C if frozen.

Research indicates Salmonella can grow at temperatures of less than 15°C, but growth is significantly suppressed at temperatures below 7°C. 

Egg pulp can be contaminated with bacteria, including Salmonella, from eggshells if these break or crack during processing, handling or transporting.

The pasteurisation process does not destroy all bacteria. The integrity of the final pasteurised product depends on the bacterial load of the pulp to be processed.

To ensure eggs are safe and suitable for consumption, it is advised to:

  • keep premises, equipment and transport vehicles effectively cleaned at least weekly
  • sanitise regularly
  • ensure good maintenance and repair
  • clean and maintain any pipes, connectors or valves used for filling and discharging egg pulp
  • use fit-for-purpose vehicles and equipment
  • adopt systems to minimise risks of eggs cracking from mechanical stresses.
Raw pulp should be transported in fit for purpose containers and equipment
Refrigerated transport and storage is essential

Inappropriate transport equipment / vehicle for whole eggs

Egg transport vehicles are designed and constructed to minimise risks of egg breakage and contamination, allow effective cleaning and sanitisation and avoid access by pests and vermin.

Vehicles and equipment used to transport eggs need regular cleaning at least once each week to prevent the build-up of Salmonella.

Salmonella can persist on eggshells, even after washing. Washing eggs can reduce bacterial load but will not remove all bacteria to make them sterile.

Any eggs transported for grading, processing, warehousing or retailer storage before the end-location for consumption, should be handled at a temperature of less than 7°C. Any hotter, and Salmonella can grow.

Correct equipment and packaging needs to be used in transporting eggs
Eggs should not be transported in inappropriate vehicles or equipment

Transportation temperature of pre-prepared egg products

Transporting pre-prepared egg products to the point of consumption, such as to a wholesaling or catering location, should occur at temperatures of less than 5°C.

Any higher than this risks bacterial proliferation if the eggs are raw or low-cooked, as there is no bacterial ‘kill’ step in the food preparation process.

Off-site preparation of raw or low-cooked egg products poses a significant risk of bacterial contamination and spread due to the extra time needed and possible temperature fluctuations that could arise from transportation delays or serving constraints.

Some epidemiological surveys have found mass catering has a high risk of causing human food-borne illness outbreaks.

If heated transportation is required, the risks of bacterial growth due to temperature fluctuations need to be closely considered. This is particularly important for Salmonella Enteritidis.

The University of Tasmania has developed a ‘Risk Ranger’ tool that can help determine food safety risks for different egg product, pathogen and processing combinations.

Be careful not to allow egg temperature to fluctuate substantially when transporting
Correct transport and refrigeration of products is crucial

Presence of yolk broken during transport and storage

Research has found the growth rate of Salmonella in egg yolk is faster than in whole eggs at all storage temperatures studied, as yolk is an excellent growth medium.
The dose of Salmonella required to cause human illness can be below 103 CFU. Some studies have found levels of 108-109 CFU/mL of the bacteria could be reached:

  1. After 3 days, at temperatures of 15°C.
  2. After 26 hours, at temperatures of 22°C
  3. After 10 hours at 37°C

It is advised to clean yolk spillages on equipment, utensils and surfaces with appropriate disinfectant or sanitiser. Fast action is needed to prevent Salmonella from growing to levels that increase the risk of cross-contamination.
Antibodies present in the yolk have little effect on the growth of some types of Salmonella, but there may be some inhibitory effect in some conditions.

It is advised to clean yolk spillages on equipment, utensils and surfaces with appropriate disinfectant or sanitiser

Presence of water / moisture on eggs

Eggs must be kept dry at all stages through the transport and storage process, as Salmonella grows faster if there is moisture than in a dry environment.

Prolonged exposure to moisture also facilitates the movement of bacteria into the egg internal contents from the eggshell. Eggshell and cuticle quality is a vital determinant of the rate of such Salmonella penetration.

Washing processes can damage the egg cuticle, putting washed eggs at a higher risk than unwashed eggs of experiencing bacterial penetration in the presence of moisture.

Eggs are not sterile, especially if dirty or contaminated with faeces, and there is a possibility that Salmonella or other pathogens will persist on the shell.

Diffusion of these pathogens into the egg internal contents can occur if there are differences in density or pressure and when the external environmental temperature is higher than the egg internal temperature.

Any external application of water or other moisture-based treatments, such as cleaning solution, to eggs must be at a temperature higher than the internal egg temperature.

Cooling systems used during processing, transport and storage should avoid eggs or associated equipment getting wet or producing condensation, which is referred to as ‘sweating’.

To limit risks of condensation, eggs are best maintained in cold-chain when they reached the required storage temperature.

If eggs are washed – the solution needs to be slightly warmer than egg internal temperature
Keep eggs dry as Salmonella grows faster in wet environments

Pasteurisation

Eggs to be pasteurised

Unacceptable, cracked and dirty eggs that are not suitable for human consumption can be pasteurised by a licensed and approved egg processor.

Pasteurisation is an industry standard for any egg pulp (defined as internal egg contents without added sugar or salt) to be sold for human consumption.

If pasteurised egg product tests positive for Salmonella, it is acceptable to re-process that batch until the required testing produces the required results. But Australian states and territories interpret these industry standards differently and it is important to check and adhere to the relevant legislation.

Pasteurised-in-shell is an alternative process used overseas where whole eggs without cracked shells are treated using a process that significantly reduces bacterial contamination on the eggshell and to the centre of the yolk.

It should be noted that pasteurisation is not a sterilisation process and its efficacy will depend on the initial microbiological load of the eggs or egg pulp.

Eggs and egg pulp to be pasteurised shall be stored at temperatures well below 7°C to minimise Salmonella growth, and processed as soon as possible after grading. Minimising the time bacteria has to grow will help to reduce the bacterial load and boost the efficacy of the pasteurisation treatment.

Cracked and dirty eggs may be pasteurised and sold for human consumption instead of rewashing

Contamination of pasteurised egg pulp

Egg pulp, which is the internal egg contents without added sugar or salt, provides an ideal growth environment for many bacterial pathogens, including Salmonella.

When exposed to air, pasteurised egg pulp can be contaminated by environmental bacteria, such as from dust or dirt. This is similar to pasteurised milk ‘going off’. 

Pasteurisation is not a sterilisation process, so bacteria can also persist in egg pulp after treatment.

For these reasons, pasteurised egg product should be treated similarly to raw egg product when exposed to the environment after storage or packaging. It is best practice to discard it after 24 hours if not stored at temperatures less than 7°C and within three days of opening, regardless of storage temperature.

Pasteurised egg product should also adhere to the commonly used ‘two-hour, four-hour’ principle of being stored in the fridge within two hours of opening and discarded after four hours of exposure to room temperature.

Ignoring this advice for pasteurised product, or using inadequate pasteurisation temperatures during processing, have been found to increase the risk of human illness from Salmonella.

Egg pulp should be stored below 7°C, and used within 3 days of opening

Whole shell eggs and pasteurised eggs in a single food product

Food preparation facilities need to ensure pasteurised egg products are used before whole-shell eggs are handled or used and avoid having both in the area at the same time.

Pasteurised eggs are at high risk of being cross-contaminated with any bacteria on the shell of the whole eggs, especially if the pasteurised product is not going to be used in the preparation of the food and will be re-stored.

Food preparation staff should wash their hands after handling whole-shell eggs, especially if they are preparing raw or low-cooked egg products.

Hand washing facilities need to be used regularly, especially between production categories

Storage after pasteurisation

Bacteria can remain in egg pulp after pasteurisation, depending on the time, storage conditions and temperature variations.

Refrigeration at temperatures less than 7°C after processing has been shown to limit Salmonella growth. 

Freezing does not destroy Salmonella, but may reduce the load, and it is recommended to store any frozen egg pulp below a temperature of -18°C.

Studies have found some foods, including liquid egg, can protect some salmonellae for several years when frozen.

Processors are required to store or transport pasteurised egg product in the recommended time and temperature conditions needed to control the growth of bacteria, such as Salmonella.

Ineffective pasteurisation process

Pasteurisation will not sterilise egg products and the process needed to be verified to comply with FSANZ or states and territories food safety guidelines. Pasteurised egg product in Australia has to be negative for Salmonella.

Food Standards Australia New Zealand (FSANZ) has a set of pasteurisation parameters that can help reduce Salmonella loads and produce a safe egg product.

Ineffective pasteurisation of egg yolk is the most significant risk to human health from contaminated or ineffectively processed pasteurised product. 

Best practices for staff in pasteurisation and grading areas

Egg grading area staff should not access pasteurisation areas for at least 24 hours before undertaking pasteurisation processes.

This can risk Salmonella being carried into the area on clothes, shoes, skin, hair and from any gut infections. Bacteria could be transferred to eggs or egg products.

Appropriate interventions, such as hand sanitising facilities and protective clothing, should be used.

Egg yolks, in particular, are an ideal growth medium for Salmonella and can easily be re-contaminated after pasteurisation.

Research has shown depending on the initial Salmonella load, it can grow to levels causing human illness within two hours if stored at room temperature.

Grading area staff should not access egg pasteurisation areas within 24 hours
hand sanitising facilities and protective clothing should be used in pasteurisation areas

Food manufacturing processes

Hot-holding of egg foods

Hot-holding, such as use of a bain-marie, is used to provide food to consumers at a warm temperature. This may not be adequate to control bacterial growth if it is at a temperature of less than 45°C.

It is recommended egg products prepared as hot dishes should be stored in a hot-holding area as soon as possible to limit cooling of the product.

Raw or low-cooked egg products, including sauces that contain eggs, retained in a hot-holding area should not be held for more than 20 minutes before consumption.

There is limited research into the 20-minute recommendation, but the assumption is bacterial growth would not be extensive during that time period in most conditions, especially if the holding temperature is 45°C or higher.

The temperature of the holding area should be checked using an external device to ensure it is operating at the required level, as in-built temperature gauges can de-calibrate.

Eggs products should be transferred to bain-marie areas as soon as possible after cooking

Dried egg product

Storage conditions for dried egg product will change, depending how effective the drying process is in removing viable bacteria, including Salmonella.

Salmonella can survive in desiccated (dry) environments and the drying process may not remove all bacteria.

There have been incidences of powdered egg being recalled due to Salmonella contamination concerns, but it is unknown whether contamination occurred pre or post-processing.

Powdered egg should be stored in a dry, cool area until reconstituted and then refrigerated. Salmonella can grow in reconstituted powdered egg product.

Salmonella can still be present in powdered egg

Refrigeration of cooked food prepared with whole shell eggs

Cooking egg products at temperatures higher than 60°C for the correct length of cooking time will typically destroy most bacteria, including Salmonella.

It is recommended food prepared with whole fresh eggs is refrigerated within two hours of preparation and discarded if held at room temperature for more than four hours.

Most salmonellae can survive at temperatures of less than 4°C and grow at temperatures higher than 7°C.

Use of preservatives can impact on the ability of Salmonella to grow in egg products. There is some evidence that Salmonella can develop resistance to some preservatives and it is recommended these are used only if fit-for-purpose.

Cooking egg products at temperatures above 60°C will destroy most bacteria

Egg cracking

If processing eggs to pulp product, it is recommended that eggs are cracked at a reasonable distance from pasteurisation plant and equipment to minimise bacterial contamination risks.

Any bacteria on the eggshell can be a source of contamination in egg pulp post-processing.

Staff and other operators handling eggshells should have limited access to the finished pulp.

To further reduce risks of contamination, it is recommended finished egg pulp is also kept a good distance away from pasteurisation and processing equipment.

Eggs due to be cracked for pulp should be stored at temperatures of well below 7°C to limit Salmonella  growth and processed as soon as possible after grading. This will help to minimise the time bacteria has to grow and reduce the bacterial load for the pasteurisation process.

There is some anecdotal evidence in Australia that Salmonella can survive in raw egg pulp that has been sent for pasteurisation.

Staff and other operators handling eggshells should have limited access to the finished pulp
Pulp egg cracking should take place away from the pasteurisation plant

Cooling and reheating pre-prepared egg products

The potential rate and load of Salmonella in re-heated food depends on the initial level of the pathogen and the temperatures used to cool and then re-heat the food.

Mass catering can pose a high risk of human food-borne illness outbreaks, according to some epidemiological surveys.

Often catered functions do not have sufficient capacity to refrigerate or re-heat foods. This increases the chances of human illness from off-site prepared egg products, particularly those that are raw or low-cooked.

Re-heating needs to be rapid so food passes quickly through the hazardous temperature range of between 5°C and 60°C.

Typically, this requires using forced air ovens, infrared or microwave re-heaters and regularly checking the temperature of the heated food.

It is recommended consumers are given clear information that a product contains raw eggs. It is best to prepare raw egg products to order at the place of consumption, refrigerate after two hours and discard after four hours at room temperature.

Research has found that Salmonella Enteritidis growth rate and presence can be high in eggs that have been subjected to fluctuations in temperature and yolk is the biggest risk, as bacteria grows most rapidly in egg yolk.

Egg should be rapidly reheated in air forced ovens, microwaves or similar

Storage

End user storage of eggs / eggs stored at room temperature during food service

Storing eggs at temperatures of less than 4°C is recommended for end-users in Australia, especially if the eggs will be used in raw or low-cooked products. This will help to maintain egg quality, limit Salmonella growth and reduce the risk of Salmonella penetrating the eggshell.

Many types of salmonellae can grow at temperatures of greater than 10°C and most will not grow below temperatures of 7°C. Bacterial load will decline over time, depending on type of pathogen and storage temperature used.

Low storage temperatures and appropriate handling techniques, including staff washing hands after handling whole eggs, are critical to limit cross-contamination to other foods in preparation areas.

Studies into some Salmonella bacteria have found eggs subjected to fluctuations in storage temperatures are at a higher risk of bacteria proliferation.

Eggs should not be out of storage areas or close to a heat source for long enough to increase internal temperatures to a level that can facilitate the growth of Salmonella, which is above 7°C.

High external temperatures can reduce egg quality, as the internal contents degrade when subjected to fluctuations in temperature.

If a recipe calls for eggs to be at room temperature before use, these should be used promptly and treated as any other perishable food item. It is recommended to discard any eggs that have been at room temperature for more than two hours.

End user storage needs to be less than 4°C
Fan units should provide adequate airflow around pallets of eggs
Staff handling end user eggs should follow strict hygiene practices

Storage temperature of eggs for pasteurisation

Eggs that are going to be pasteurised should be stored at temperatures less than 7°C to minimise risks of bacteria being able to proliferate into the internal content and affect quality.

This is especially important if eggs are being taken off-site and will not be pasteurised for some time.

It should be noted the pasteurisation process does not kill all bacteria, as it is not a sterilisation process. This means it is important there is only a low bacteria load before the process starts to have a meaningful reduction through pasteurisation.

Studies indicate reducing egg storage time before pasteurisation and avoiding temperature fluctuations can reduce consumer risk of illness.

Eggs to be pasteurised need to be stored below 7°C

Storage temperature of chilled raw foods

Food-borne illness outbreaks involving raw or low-cooked eggs typically involve consumption of products that have been subjected to temperature fluctuations.

Studies have found some types of dishes may pose a higher food safety risk.

The rate of Salmonella contamination in Australia is estimated to be less than one egg per 20,000. But any situation that allows bacteria to proliferate increases the risk of human illness from raw egg food.

It is recommended raw egg foods, prepared with pasteurised egg or not, should be kept at temperatures less than 4°C and discarded at the end of the food service day. This needs to be no longer than 24 hours from time of manufacture, as the risk from cross-contamination from raw eggshells in a food preparation area is high.

Salmonella can grow well in eggs subjected to fluctuations in temperature, indicating raw egg foods should be stored and maintained in refrigerated conditions as soon as possible. It is undesirable to have constant retrieval of raw egg food from refrigerated conditions to room temperature and back.

Pasteurisation is not a sterilisation process and does not destroy all bacteria. But the risks associated with producing raw egg products can be reduced by using pasteurised product.

Salmonella on eggshells, or remaining in the pasteurised egg product, can transfer into the raw egg product and grow. This is a bigger risk if the food is held at temperatures of between 5°C and 60°C.

Raw egg food products are a higher risk

Storage of dried / powered egg product

Salmonella can survive in desiccated environments and the drying process may not totally remove the bacteria.

Storage of dried and powdered egg product should adhere to manufacturer instructions. These will be based on an assessment by the manufacturer or egg processor of the efficacy of the drying process in removing viable bacteria, including Salmonella.

There have been cases of powdered egg being recalled due to Salmonella contamination concerns. But it was unknown whether contamination occurred pre or post-processing.

It is recommended powdered egg be stored in a dry cool area until reconstituted, where it should be kept refrigerated and be treated similarly to liquid pasteurised pulp. This is because Salmonella can grow in reconstituted powdered egg product. 

Salmonella can still be present in powdered egg

Ineffective stock rotation

Producers, processors, wholesalers and food service stakeholders are advised to sell or use first the eggs that have been stored for the longest time. This applies to all parts of the through-chain.

The longer Salmonella persists on eggs, the higher the contamination risk, as it can diffuse into the internal contents.

Yolk Mean Time (YMT) measures the length of time yolk membrane takes to breakdown. If Salmonella is present in the egg internal contents when the YMT is reached, the bacteria may be able to enter the yolk easier. Yolk is an ideal growth medium for Salmonella.

Salmonella levels on eggshells decline rapidly in refrigerated storage conditions, at temperatures of about 4°C, with no persistence after about four weeks.

Storage at room temperature can increase the persistence of Salmonella on eggshells. Although studies have found total bacterial count tends to remain constant or increase and Salmonella is unlikely to persist after four weeks on eggs for any storage conditions.

This indicates older eggs may be at lower risk of Salmonella persisting on the eggshell than newer eggs.

But, antibacterial properties in the egg degrade over time, which puts older eggs at higher risk of Salmonella growth in the internal egg contents if processing or storage conditions have enabled bacteria to penetrate the eggshell.

At temperatures above 15°C for one hour, there can be measurable Salmonella growth, which also occurs if there are storage temperature fluctuations. Eggs stored above 15°C should be sold as soon as possible.

Extraneous matter, such as faeces, feathers or dirt, on the eggshell can significantly increase Salmonella persistence and eggshell penetration.

It is recommended all eggs, regardless of age, washed or unwashed, are stored at temperatures less than 7°C. This will inhibit Salmonella growth. Eggs stored above 15°C should be sold as soon as possible.

Egg stock needs to be monitored and rotated
Eggs sold in supermarkets should be rotated daily

Ineffective cool room temperature and humidity control

Storage temperature and humidity have a big influence on egg quality, but not necessarily on egg food safety.

It is recommended robust temperature and humidity control is used in storage areas to maintain egg quality and limit bacterial growth when seasonal and environmental conditions fluctuate. This needs to be balanced to ensure eggs do not form condensation on the eggshell, or ‘sweat’, which can promote bacteria movement to egg internal contents.

Salmonella can grow at temperatures less than 15°C, but most  will stop growing at temperatures of 7°C or less. This may not destroy all bacteria, but will limit its growth.

It should be noted that storing eggs at or below temperatures of 7°C or 15°C may not always be sufficient to avoid condensation forming when they are removed from storage, such as in high humidity environments.

Humidity levels of about 60-70 per cent are considered appropriate for most environments to prevent condensation and limit bacterial growth. But environmental factors are a major factor, including outside humidity.

It is recommended storage and transport temperature and humidity are monitored regularly. This includes use of external monitors, as some in-built monitors can de-calibrate over time and compromise accuracy.

Cool rooms need to have adequate cooling capacity
Temperature control for storing washed eggs

Sale of eggs

Sale of cracked and or dirty eggs

Primary producers, wholesalers, retailers and any other business that handle eggs shall not sell visibly cracked, broken or dirty eggs. This is prohibited by federal and state government legislation.

Well managed tactics are needed to minimise potential for eggshell cracking at any stage of through-chain, especially from mechanical stress where there is force applied to eggs.

Every time eggs are subjected to a mechanical stress, there is a risk of shell fractures that can lead to cracks.

There is more potential for Salmonella to penetrate the eggshell if cracks are present. But there is limited research into the size of the crack that will pose a risk, as some Salmonella strains can penetrate intact eggshells.

Sale of cracked or dirty eggs is prohibited
Mechanical stress can cause micro cracks in eggs

Best before 42 days

It is recommended to use eggs before its ‘best before’ date. This is a period of six weeks or less from the time of packing but applies only to eggs maintained at optimal temperature conditions.

There are no legal requirements for eggs to have a ‘best before’ date of 42 days, unless requested by a customer. The 42-day recommendation stems from industry experience and relates to maintaining optimal egg quality, not to egg food safety issues.

The ‘best before’ date is considered to start from the date of pack, rather than the date of lay.

This has potential negative implications for food safety issues, as eggs may be re-packed and contaminated by Salmonella at any stage of the through-chain. This may distort the estimated perception of egg quality or safety.

Salmonella does not typically persist on eggshells for more than four weeks, so older eggs may have less Salmonella load on the eggshell than new eggs. This is assuming re-contamination has not occurred in the through-chain and that the eggs have been stored appropriately.

Antibacterial efficacy of the egg drops over time, along with the quality of the internal contents, due to water loss and protein degradation. This can increase the risk of Salmonella causing human illness if the bacteria has been able to contaminate the internal contents and migrate to the yolk.

All egg cartons should have a ‘best before’ displayed”
Eggs sold in supermarkets should be rotated daily

Egg recall

All producers, processors, wholesalers and retailers need a process in place in case of an egg recall.

Industry recommends producers, in particular, have a robust supply identification, withdrawal and recall plan in case their eggs are linked to a food-borne illness outbreak.

This process aligns with Food Standards Australia and New Zealand (FSANZ) recommendations for egg producers to have a system of identifying who has bought their eggs or egg pulp.

It should be noted, different states and territories may interpret the FSANZ standards differently. State legislation will reflect this and should be taken into consideration when assessing risks.

Egg usage and handling by customers

It is important producers understand how eggs will be used by their customers when developing risk management strategies for their business.

If customers produce high risk egg products, such as raw egg sauces, it can increase the chance of being investigated by authorities in the event of a salmonellosis outbreak.

This may occur even if the producer has taken all reasonable measures to manage Salmonella risks.

It is recommended producers provide advice to their customers, such as in written material or pamphlets, about correct egg handling, transport, storage and preparation techniques. This can be especially important if there are concerns about customer practices that may increase risks of food-borne illness outbreaks.

Risk management strategies should identify customer end use