Eggs and Salmonella
There has been a debate going on for years about, should eggs be refrigerated. For those of you that don’t know, the US 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 fridge, it is the law. The US 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. This is because eggs undergo a different process before they hit the shelves in the US. The reason we need to keep our eggs in the fridge is that the eggs undergo a specific cleaning process before you are able to 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”.
By 1970, the U.S. had perfected an egg washing system that was easy, effective, and produced clean eggs. There was one catch, after washing the eggs had to be refrigerated. The trade-off for clean, spotless, and bacteria-free eggs is that washing also 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 types of bacteria to enter the egg. That is why eggs are handled differently in the US. without the cuticle, eggs need to be kept cold to discourage bacterial growth. This process also extends the shelf life of eggs by about 2 weeks, totaling about 40 days. Remember once the egg is washed, it has to be refrigerated.
Different Types of Eggs
Standard White Eggs
These eggs come from white hens that are typically raised in conventional housing systems. Conventional housing has been the standard for decades, but the Alberta egg industry has begun to transition away from conventional housing systems.
Standard Brown Eggs
These eggs come from brown hens that are typically raised in conventional housing systems. Conventional housing has been the standard for decades, but the Alberta egg industry has begun to transition away from conventional 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.
These eggs come from hens that are 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.
These eggs come from hens that are raised in free-run (barn or aviary) housing systems, which also provide access to outdoor runs (when weather permits).
These eggs come from hens that are raised in free-range housing systems. The hens are only provided feed that has been certified organic, which means that it only contains ingredients that were grown without pesticides, herbicides, or commercial fertilizer. Look for a certified organic symbol on the egg carton.
These eggs come from hens that were provided feed containing extra flax (up to 10-20%). As a result, the eggs laid by these hens contain more Omega-3 fatty acids.
These eggs come from hens that were provided feed that was nutritionally enhanced to include higher levels of certain vitamins (ie: Vitamin D or Vitamin E). As a result, the eggs laid by these hens contain corresponding higher amounts of the particular vitamin(s).
These eggs come from hens that were provided feed containing only plant-based ingredients.
Liquid, frozen and dried egg products come from eggs that were broken by special egg breaking machines, and then pasteurized. They often contain added ingredients (ie: preservatives, flavoring, or coloring) and this process allows for special formulations (ie: egg whites only).
Maintaining egg 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, then it is as fresh.
- If it sinks but stands on its end, then it is still good to eat but getting 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.
- If the yolk stands really tall after you’ve cracked the egg, it is fresh.
- If the yolk has wrinkles or dissolves into a puddle when you crack it open, then 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, which is 62% of the recommended daily intake (RDI).
The case for washing before buying
Studies have shown that washing eggs before reaching shelves prevent Salmonella from entering the inside of the egg.
Took a look at hundreds of eggs and experimented with the if a washing technique is used to clean the eggs before reaching consumers there would be less salmonella. Its results showed that:
- 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.
Another study looked at if washing eggs have a greater effect on salmonella than non-washed eggs. They concluded that:
- 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 that there was no significant difference in the survival rate of S. Typhimurium on the eggshell surface of washed and unwashed eggs.
- Found that S. Typhimurium strain 2 penetration was significantly higher in washed eggs than unwashed eggs.
Meta-analysis of whether washing eggs had any statistical effect on salmonella.
- As this literature review shows, the master key to reduce the likelihood of getting ill from Salmonella in eggs from the point of the consumer is to buy Salmonella-free eggs.
- The large 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 acceptable 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. Salmonella lives in human and animal intestines and are shed through feces.
People are usually affected through 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.
Signs and symptoms can last anywhere from 2 to 10 days. Onset of symptoms can be anywhere from 6 hours to 6 days. Commonly associated with the stomach flu
- Abdominal cramps
- Blood in the stool
- Wash your hands
- Proper raw meat and poultry handling
- Proper food storage
- Clean your cutting board