Consuming raw or undercooked eggs potentially causes Salmonella infection, which can pose severe, sometimes life-threatening, health risks, especially to susceptible populations. During August 2017 to August 2020, the Centre for Food Safety has received referrals of more than 300 food poisoning outbreaks related to food premises, involving nearly 1000 victims, caused by Salmonella species.
Both the outside and the inside of eggs can be contaminated with Salmonella. Egg shells can be contaminated with faecal matter and germs may enter through pores or cracks on the shell of eggs. Moreover, Salmonella can be introduced to the egg from infected reproductive tissues of poultry prior to shell formation. Eggs contaminated with Salmonella may look normal.
To assist the food trade in preventing food poisoning due to Salmonella in eggs and egg products, the Centre for Food Safety gives out practical food safety advice about using eggs in food preparation:
Choose safe raw materials
Purchase eggs from reliable sources and only accept eggs that are clean without cracks or leakage.
For dishes that often use lightly cooked or uncooked eggs, choose pasteurised eggs, egg products or dried egg powder. Pasteurisation is the process of applying low heat to kill pathogens and inactivate spoilage enzymes.
Storing and handling of raw eggs
- Shell eggs should be stored in a cool, dry place, ideally in the refrigerator, and used on a first-in-first-out basis.
- Wash hands thoroughly before and after using eggs. All utensils and other food contact surfaces such as whisks, bowls and benches should be cleaned and sanitised every time before handling eggs and egg products.
- Washing shell eggs is unnecessary because this facilitates the entry of bacteria from the outside of the shell to inside the egg through the pores in the shell.
- When separating the yolk from the white, it is better to use a clean egg separator instead of the egg shell which may contain traces of Salmonella on the surface.
Pooling eggs is a high-risk practice when preparing egg dishes
- Pooling refers to the practice of breaking a number of eggs into containers and using the combined eggs to make multiple servings of egg dishes or for use in multiple recipes.
- Pooling is a common practice in some restaurants to save time and control portion size. However, pooling eggs can allow one or more infected eggs to contaminate the whole pool of eggs. If people consume egg dishes prepared from the pool without thorough cooking, they may get food poisoning.
- Restaurants should only break enough eggs for immediate service in response to a consumer’s order.
- If choose to break eggs for later use, keep the pooled eggs in covered containers in the refrigerator and only take out the amount as needed.
- Use all pooled eggs on the same day and do not top up with new eggs.
- As pooled eggs have a higher chance of harbouring bacteria, they should be cooked thoroughly and not be used for making raw or lightly cooked dishes.
Cook eggs thoroughly and keep them at a safe temperature
- The best way of eliminating harmful bacteria is to cook the eggs thoroughly until the core temperature reaches 75°C or the yolks are firm.
- If not consumed immediately after preparation, hot dishes such as soft-scrambled eggs should always be served or kept at above 60°C, and cold dishes such as sandwiches and desserts should be kept at 4°C or below.
The above advice is applicable not only in food businesses but also in domestic settings to reduce risks of food poisoning.
Periodical and Publication
Food Safety Focus
- Preparation of Eggs and Egg Products – Safety First (October 2020)
- Food Poisoning Caused by Salmonella in Sandwiches Containing Eggs (August 2020)
- Food Poisoning Caused by Salmonella in Soft-scrambled Eggs at Improper Cooking and Holding Temperature (July 2019)
- Bacteria on Eggs – Should Eggs be Washed? (December 2008)