Eggs as food

• 1. Millennia Of Consumption

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  Humans and other hominids have consumed eggs for millions of years. The most widely consumed eggs are those of fowl, especially chickens. People in Southeast Asia began harvesting chicken eggs for food by 1500 BCE. Birds were domesticated before 7500 BCE to provide these valuable foodstuffs. Chickens arrived in Sumer and Egypt by 1500 BCE and reached Greece around 800 BCE. In ancient Rome, meals often started with an egg course. Romans crushed shells on their plates to prevent evil spirits from hiding there. The tomb of Haremhab in Thebes dates to approximately 1420 BCE and shows a man carrying bowls of ostrich eggs as offerings. During the Middle Ages, eggs were forbidden during Lent because of their richness. An annual pause allowed farmers to rest their flocks and limit feed consumption when stocks were scarce. Eggs scrambled with acidic fruit juices became popular in France in the seventeenth century. This dish may have been the origin of lemon curd.

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• 2. Global Production And Industry

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  Mass production of chicken eggs is now a global industry. In 2009, an estimated 62.1 million metric tons of eggs were produced worldwide from a total laying flock of approximately 6.4 billion hens. World production of chicken eggs reached 80.1 million tonnes in 2017. China led this output with 31.3 million tonnes while the United States contributed 6.3 million. India followed with 4.8 million tonnes and Mexico added 2.8 million. Japan produced 2.6 million tonnes and both Brazil and Russia supplied 2.5 million each. The largest egg factory in British Columbia ships 12 million eggs per week. For January 2019 alone, the United States produced 9.41 billion eggs. Of these, 8.2 billion went for table consumption and 1.2 billion were used for raising chicks. Americans are projected to consume 279 eggs in 2019. This figure represents the highest consumption since 1973 but remains less than the 405 eggs eaten per person in 1945. Asian production provided 59 percent of the world total in 2013.

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• 3. Anatomy And Grading Systems

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  Bird and reptile eggs consist of a protective eggshell, albumen, and vitellus contained within thin membranes. The yolk is suspended by spiral bands of tissue called chalazae which mean hailstone or hard lump in Greek. Chicken eggs resemble a prolate spheroid with one end larger than the other. The larger end contains an air cell that forms when contents cool down after laying. A very fresh egg has a small air cell and receives a grade of AA. As the air cell increases due to water loss through shell pores, the grade moves from AA to A to B. An old egg will float in water and should not be eaten if it smells foul. Eggshell color results from pigment deposition during formation. Brown pigment is protoporphyrin IX while blue pigment is biliverdin. Generally chickens with white ear lobes lay white eggs whereas those with red ear lobes lay brown eggs. Although no link exists between shell color and nutritional value, cultural preferences often dictate demand. Brown eggs have a significantly higher incidence of blood spots because candling is less effective with them.

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• 4. Culinary Science And Preparation

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  Eggs contain multiple proteins that gel at different temperatures within the yolk and the white. Egg yolk becomes a gel between 65 degrees Celsius and 70 degrees Celsius. Egg white gels at different temperatures depending on its specific protein composition. Salmonella is killed instantly at 71 degrees Celsius but also dies from 63 degrees Celsius if held for sufficiently long periods. To avoid salmonella issues, eggs may be pasteurized in-shell at 64 degrees Celsius for an hour and 15 minutes. If a boiled egg is overcooked, a greenish ring appears around the yolk due to changes in iron and sulfur compounds. Peeling a cooked egg is easiest when put into boiling water rather than slowly heating from cold water. In February 2025 scientists published research confirming periodic cooking preserves distinct textures. This method requires alternating between boiling and lukewarm water eight times. Ground eggshells sometimes serve as food additives to deliver calcium. Every part of an egg is edible although shells are generally discarded. Some recipes call for immature or unlaid eggs harvested after slaughter while still inside the chicken. The albumen contains protein but little fat and can form foams used in meringues.

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• 5. Nutrition And Health Debates

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  A medium large chicken egg provides approximately 70 kilocalories of food energy and 6 grams of protein. Cooked eggs supply several vitamins including vitamin A riboflavin pantothenic acid vitamin B12 choline phosphorus zinc and vitamin D. More than half the calories found in eggs come from the fat in the yolk. Five grams of fat exist in 50 grams of chicken egg which classifies as large in the US. There is debate over whether egg yolk presents a health risk. Some research suggests dietary cholesterol increases the ratio of total to HDL cholesterol adversely affecting profiles. Other studies show moderate consumption up to one a day does not increase heart disease risk in healthy individuals. Harold McGee argues that saturated fat raises cholesterol levels more likely than consuming cholesterol itself. Studies have shown conflicting results about connections between egg consumption and type 2 diabetes. A 2013 meta analysis found eating four eggs per week associated with a 29 percent increase in relative risk of developing diabetes. Another 2013 meta analysis supported this idea while a 2016 review suggested the association may be restricted to United States cohort studies. A 2020 meta analysis found no overall association between moderate consumption and diabetes risk.

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• 6. Animal Welfare And Farming Ethics

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  Commercial factory farming operations often involve raising hens in small crowded cages preventing natural behaviors like wing flapping or dust bathing. Many hens confined to battery cages are debeaked to prevent cannibalism causing severe pain where some may refuse to eat. Laying hens are euthanized when reaching 100 to 130 weeks of age when productivity declines. Male birds of laying strains do not lay eggs and are not suitable for meat production so they generally are killed soon after hatching. Effective the 1st of January 2012 the European Union banned conventional battery cages for egg laying hens as outlined in EU Directive 1999/74/EC. The EU permits enriched furnished cages that must meet certain space requirements. In all methods of egg production unwanted male chicks are killed at birth during securing further generations of egg laying hens. As of June 2023 this practice has been banned in Germany France Luxembourg and Italy. Some producers use in-ovo sexing technology to analyze chick sex before hatching allowing removal of male eggs from incubation. As of April 2025 five companies offer commercially available in-ovo sexing technology used for 28 percent of the European layer population.

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