Eggs and Salmonella

Eggs and Salmonella

There has been a debate going on for years about, should eggs be refrigerated and if eggs salmonella plays a role in it. For those of you that don’t know, the U.S. is one of the only countries that keeps eggs in a fridge. 

It is not a choice whether you should keep your eggs in the refrigerator; it is the law. The U.S. Department of Agriculture requires eggs to be refrigerated. Should we refrigerate our eggs?

Why do some countries refrigerate their eggs?

In America, food safety officials emphasize that once eggs have been refrigerated, it is critical they remain that way. A cool egg at room temperature can sweat, facilitating the growth of bacteria that could enter the egg through its porous shell. 

This bacteria is usually Salmonella. It is because eggs undergo a different process before they hit the shelves in the U.S. We need to keep our eggs in the fridge because the eggs undergo a specific cleaning process before you can buy them. 

“The U.S. Department of Agriculture (USDA) determined that the best way to fight Salmonella contamination is by sanitizing the eggs before they reach the consumer. The washing process removes contaminants, but it also removes the natural coating of the egg, leaving the shell porous. 

On U.S. commercial egg farms, it is required that eggs are thoroughly washed and immediately refrigerated before they leave the farm and during transportation to the grocery store” [1]

By 1970, the U.S. had perfected an egg washing system that was easy, effective, and produced clean eggs. After washing, there was one catch: the eggs had to be refrigerated. The trade-off for clean, spotless, and bacteria-free eggs is that washing removes a thin, filmy, protective outer layer called the cuticle. 

This cuticle is a semi-permeable layer that keeps bacteria out of an egg while letting oxygen circulate. Without this layer, the egg becomes more permeable, allowing different bacteria to enter the egg. 

That is why eggs are handled differently in the U.S. without the cuticle; eggs need to be kept cold to discourage bacterial growth. This process also extends the shelf life of eggs by about two weeks, totaling about 40 days. Remember, once the egg is washed, it has to be refrigerated. 

Different Types of Eggs

Did you know that there is more than one type of egg out there other than the usual white ones you eat? Here’s what you need to know [2].

Standard White Eggs

These eggs come from white hens typically raised in conventional housing systems. For decades, traditional housing has been the standard, but the Alberta egg industry has transitioned from conventional housing systems.

Standard Brown Eggs

The standard brown eggs come from brown hens typically raised in conventional housing systems. For decades, traditional housing has been the standard, but the Alberta egg industry has transitioned from traditional housing systems.

Furnished / Enriched / Nest-Laid Eggs

These eggs come from hens that are raised in furnished housing systems. Furnished housing provides more space (both floor space and height) for the hens to move around while also providing a variety of enrichment, which allows the hens to express more natural behaviors. Enrichments include nesting boxes, perches, scratch pads, and dust baths.

Free-Run Eggs

Free-run eggs come from hens raised in free-run (barn or aviary) housing systems. Free-run systems allow the hens to roam freely within an enclosed barn while also providing a variety of enrichments such as nesting boxes and perches. 

Free-Range Eggs

These eggs come from hens raised in free-run (barn or aviary) housing systems, which also provide access to outdoor runs (when weather permits).

Organic Eggs

These eggs come from hens that are raised in free-range housing systems. The hens are only provided feed that has been certified organic. It means that it only contains ingredients grown without pesticides, herbicides, or commercial fertilizer. Look for a certified organic symbol on the egg carton.

Omega-3 Eggs

Omega-3 eggs come from hens provided feed containing extra flax (up to 10-20%). As a result, the eggs laid by these hens contain more Omega-3 fatty acids.

Vitamin-Enhanced Eggs

These eggs come from hens that were provided nutritionally enhanced feed to include higher levels of specific vitamins (i.e., Vitamin D or Vitamin E). As a result, the eggs laid by these hens contain corresponding higher amounts of the particular vitamin(s). 

Vegetarian Eggs

This type of egg comes from hens that were provided feed containing only plant-based ingredients.

Processed Eggs

Liquid, frozen, and dried egg products come from eggs broken by special machines and pasteurized eggs. They often contain added ingredients (i.e., preservatives, flavoring, or coloring), and this process allows for special formulations (i.e., egg whites only).

Maintaining the Egg’s Freshness

It’s a bit disturbing to know that some eggs end up sitting on a shelf somewhere for up to six weeks before you buy them.

The Float Test

  • If you put an egg in a bowl of water and it sinks to the bottom and lays on its side, it is as fresh.
  • An egg that sinks is still good to eat but it is only older.
  • If it floats to the top of the water, do not eat it; it’s an old egg.

Other Ways to Tell If an Egg Is Fresh

  • If the shell seems unusually thick, then it is fresh.
  • When the yolk stands tall after you’ve cracked the egg is still a fresh egg.
  • If the yolk has wrinkles or dissolves into a puddle when you crack it open, it is an old egg.

Should You Eat Eggs Every Day?

Science says that up to 3 whole eggs per day are perfectly safe for healthy people. A single medium-sized egg contains 186 mg of cholesterol, 62% of the recommended daily intake (RDI).


The case for washing before buying

Studies have shown that washing eggs before reaching shelves prevents Salmonella from entering the inside of the egg.

Study 1

Take a look at hundreds of eggs and experiment with the if a washing technique is used to clean the eggs before reaching consumers, there would be less Salmonella. Its results showed that [3]:  

  • When undertaken according to a strictly controlled set of best practice conditions, washing eggs that have been contaminated with Salmonella before cuticle hardening does not lead to contamination of contents with these pathogens.
  • Careful temperature regulation has to be used to inhibit salmonella entrance into the egg.

Study 2

Another study examined if washing eggs have a more significant effect on Salmonella than non-washed eggs. They concluded that [4]:

  • The penetration of bacteria across the eggshell is dependent on the survival of bacteria on the eggshell surface and egg storage conditions. Results from this study indicated no significant difference in the survival rate of S. Typhimurium on the eggshell surface of washed and unwashed eggs.
  • Found that S. Typhimurium strain two penetration was significantly higher in washed eggs than in unwashed eggs.

Study 3

Meta-analysis of whether washing eggs had any statistical effect on Salmonella [5].

  • As this literature review shows, the master key to reducing the likelihood of getting ill from Salmonella in eggs from the consumer’s point is to buy Salmonella-free eggs.
  • The majority of consumers do not have access to eggs with this guaranteed Salmonella-free status. When purchasing/collecting and using these eggs in cooked dishes, three practices will together reduce Salmonella to sufficient numbers: (1) washing hands after touching dirty eggs or egg contents to avoid ingestion of spilled raw eggs, (2) assuring a proper control of cooking time and temperature, monitored by reliable methods, and (3) cleaning of surface that has been in contact with dirty eggshells or egg containments.

What is Salmonella?

Salmonella is a bacterial infection that usually affects the intestinal tract. It lives in human and animal intestines and is shed through feces. 

People are usually affected by contaminated food or water, usually through uncooked meats, poultry, eggs, and egg products. 

CDC estimates Salmonella bacteria cause about 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States every year. Food is the source of most of these illnesses [6].


Signs and symptoms can last anywhere from 2 to 10 days. The onset of symptoms can be anywhere from 6 hours to 6 days. Commonly associated with the stomach flu [7].

  • Nausea
  • Vomiting
  • Abdominal cramps
  • Diarrhea
  • Fever
  • Chills
  • Headache
  • Blood in the stool


  • Wash your hands
  • Proper raw meat and poultry handling
  • Proper food storage
  • Clean your cutting board

Want to know which eggs are the healthiest? Click here for the full episode 👇


0:00 Introduction with the Hosts/Affiliates/Updates
1:32 Eggs and Salmonella
2:20 Why do some countries refrigerate and wash their eggs?
5:16 Different Types of Eggs
5:21 Standard White Eggs and Standard Brown Eggs
8:54 Free-Run Eggs and Free-Range Eggs
9:26 Organic Eggs
10:15 Omega-3 Eggs and Vitamin-Enhanced Eggs
12:00 Vegetarian Eggs and Processed Eggs
14:33 Should you eat eggs every day?
16:01 Maintaining Eggs Freshness
18:06 What is a Salmonella
18:20 Signs and Symptoms
20:20 Prevention
22:25 Closing Statement of Hosts

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