Chicken eggs are nutritious, tasty and affordable. They are served in home-cooked meals in many households. Still, there are doubts about the food safety of eggs. For instance, should we wash the chicken eggs before storing? Is it necessary to keep them in a refrigerator? What are the potential health risks of eating soft scrambled eggs and soft-boiled eggs?

Is it necessary to wash chicken eggs before storing?

When a chicken lays an egg, the eggshell might be contaminated with bacteria of fecal matter, such as passing through the cloaca of the chicken. Eggshell has a thin outermost protective coating called cuticle to prevent bacteria from penetrating the egg through the tiny pores on the eggshell. If the egg is not consumed soon after washed, bacteria can easily travel across the tiny holes on the outside of the egg and enter the inside, thereby accelerating its spoilage. Therefore, it is not advisable to wash chicken eggs before storing.

In general, the packaged chicken eggs bought from supermarkets have gone through specific cleaning procedures in their commercial processing before they are placed on shelves for sale. However, the eggs sold in bulk may be usually unclean. If the eggshells are very dirty, it needs to wipe the eggs with a dry cloth or paper towel before storing them in a refrigerator or keeping them in a separate storage box so as to prevent the eggs from contaminating other food items. If it is necessary to wash the egg, cook it right away after washing.

Should chicken eggs be stored in the refrigerator?

Chicken eggs are perishable so it is best to store them in the refrigerator, in which low-temperature can inhibit the growth of bacteria like Salmonella spp. Always remember to keep cooked food above raw food in the refrigerator. Moreover, once the eggs have been refrigerated, they must be kept refrigerated to avoid “Sweating” of eggs, which is the phenomenon of condensed water sitting on the surface of eggshells caused by temperature changes. This condensation makes it easier for bacteria to penetrate the eggshell through its pores and contaminate the inside of the egg. Always follow the “First-In, First-Out” principle, so that chicken eggs and egg products which are close to their expiry dates will be consumed in a timely manner.

What are the risks of eating partially cooked eggs?

The inside and outside of chicken eggs may be contaminated with pathogens, like Salmonella spp. and Escherichia coli. It is hard to tell whether the egg is contaminated because its appearance looks normal. Consumption of undercooked chicken eggs (e.g. soft scrambled eggs, soft-boiled eggs and eggs Benedict), sauces and spreads prepared with raw chicken eggs (e.g. mayonnaise and dipping sauce for hot pots) or desserts prepared with chicken eggs which are not fully-cooked (e.g. tiramisu, mousse, soufflé and cheesecake) can result in foodborne diseases. For safety purpose, always use pasteurised eggs and egg products for preparing aforesaid food items. Pasteurisation is a heat-treatment and heats the eggs to a specific temperature for a set period of time so as to eliminate the pathogens in eggs without cooking the contents of the egg. It can significantly reduce food safety risks associated with dishes prepared with undercooked chicken eggs.

In addition, the elderly, young children, pregnant women and people with weakened immune systems should avoid raw or undercooked eggs and egg products. We should always wash our hands thoroughly after touching or handling chicken eggs, wipe them dry properly, and maintain personal and environmental hygiene. Always use separate utensils for raw food and cooked food while handling chicken eggs to avoid cross-contamination, and make sure that chicken eggs are thoroughly cooked to ensure food safety.

Shopping tips:

ü       Never buy cracked chicken eggs because bacteria can enter the eggs through the cracks on the shells;

ü       Do not buy chicken eggs with shells soiled with fecal matter, dirt or adhered feathers;

ü      Check whether the outer packaging of chicken eggs is marked with the “Use by Date” or “Best before Date”, and select accordingly based on the dates;

ü       Do not buy chicken eggs in large quantities for the sake of convenience. Purchase an appropriate amount based on actual needs and eat the eggs as soon as possible.

Chicken eggs are tasty and nutritious. Is it beneficial to eat one egg per day?

Chicken eggs are very nutritious, providing the nutrients needed by the human body, such as vitamin D, vitamin E, folic acid and high bioavailable proteins. People usually worry about the cholesterol in chicken eggs and avoid eating egg yolks. Indeed, studies in recent years have revealed that eating chicken eggs does not raise cholesterol levels in our body, and the whole chicken egg should be eaten to get balanced nutrition. Hence, consumers should be aware that it is important to take a variety of foods for ensuring a balanced intake of multiple nutrients and maintaining healthy diet.

For more information, the food industry can refer to: “Hygiene Guidelines on the Preparation and Supplies of Eggs and Egg Products” (Chinese version only). 

Leaflet: Eat Chicken Eggs Without Worry (Chinese version only)