Interesting facts about eggs 

What causes double yolk in eggs?

Double-yolk eggs are eggs that contain two yolks within a single shell. These occur when a hen, typically young or new to egg production, releases two yolks into the same eggshell rather than the usual one yolk. This phenomenon can happen when young hens often have irregularities in their reproductive systems. These hormonal changes can sometimes cause the release of two yolks simultaneously. Genetic factors could also make some chicken breeds more prone to producing double-yolk eggs. Breeds that are larger or bred for increased egg production may experience this occurrence more frequently. Lastly, as hens age, their reproductive systems can become less consistent, leading to variations in egg production. Double-yolk eggs may become more common in older hens.

How long can you store eggs in the refrigerator?

Eggs can be safely stored in the refrigerator for a period of three to five weeks starting from the day they are placed in the fridge. Even though the “Sell-By” date may pass within this timeframe, the eggs remain perfectly safe for consumption.

Free Range or Caged Eggs?

Research suggests that free-range eggs offer potential health benefits compared to caged eggs. This is because the hen’s diet influences the egg’s nutritional profile, and free-range hens, which enjoy a more diverse range of foods, tend to produce eggs with a higher proportion of unsaturated fats, increased omega-3 fatty acids, and enhanced vitamin content.

Are there chemical residues in eggs?

The presence of chemical residues in eggs can vary depending on a range of factors, including the farming practices, the feed given to the chickens, and other. Chickens raised for egg production may be exposed to pesticides or herbicides if they consume contaminated feed or water. These chemicals can leave residues in eggs. Additionally,  antibiotics and veterinary drugs are sometimes administered to chickens to prevent or treat diseases. Environmental Contaminants: Chickens raised in areas with high levels of environmental pollution may be exposed to contaminants like heavy metals (e.g., lead, cadmium) or persistent organic pollutants (e.g., dioxins, PCBs). These contaminants can accumulate in chicken tissues, including eggs. 

Keep in mind that such cases are quite rare as regulatory agencies typically set strict limits on chemical residues in food products, including eggs, to ensure they are safe for consumption. 

Why are some eggs white and some brown? 

Different chicken breeds have genetic traits that result in specific shell colors. For example, Leghorn chickens typically lay white eggs, while Ameraucana chickens lay blue or greenish-blue eggs, and Rhode Island Red chickens lay brown eggs.

Within a breed, individual chickens may vary slightly in the shade of their eggshells due to genetic factors. Some may produce slightly lighter or darker eggs.

The color of an eggshell is influenced by pigments deposited on the surface of the shell during its formation. For example, brown eggshells get their color from a pigment called protoporphyrin. Chickens with a higher concentration of this pigment in their diet tend to lay darker brown eggs. Last years, in some egg production units, they started painting white eggs in order to look like brown eggs

The diet of a chicken can affect the color of the eggshell to a limited extent. For example, if a chicken’s diet is rich in certain pigments, such as marigold petals or alfalfa, it may produce eggs with more vibrant yolks and potentially slightly darker eggshells. We already know that grass and other plants, such as clovers, enhance the yellowish colour of the yolk

As hens get older, the color of their eggshells may change slightly. For example, some hens that lay brown eggs may produce lighter-colored eggs as they get older.

A chicken’s overall health and stress levels can influence its eggshell’ quality and color intensity. Healthy, well-cared-for chickens are more likely to produce eggs with consistent colors.

Further reading

Poultry Egg Types

What affects the quality and size of the eggs?

Eggs: Nutritional Value & Health Benefits

Classification, Marking and Labelling of Eggs

References

https://ask.usda.gov/