Why do some duck eggs turn blood red?

Mr. Truong Chi Thien, director of Vinh Thanh Dat Company (Ho Chi Minh City), a leading supplier of clean poultry eggs in Vietnam, said that the discoloration of the egg white only occurs in duck eggs and has never appeared in chicken eggs. The color may be slightly pink or dark pink, rarely red. The company has also repeatedly sent samples of eggs with pinkish egg whites for testing, but no harmful chemicals have been detected.

The fact that fertilized duck eggs turn red when boiled has caused confusion and concern among many people.

According to Mr. Thien, there are two reasons why duck egg whites change color. Firstly, the egg is in the process of transitioning from fresh to spoiled; a pink or red color will appear before the egg white completely turns black. During this process, the egg will release hydrogen sulfide gas with a pungent odor. If the egg doesn't crack when boiled, the smell will still linger after peeling. Secondly, people raise ducks not using industrial methods, but allowing them to roam freely in the fields and eat natural food.

"Some components in food affect egg formation, resulting in excess or deficiency of certain nutrients. Therefore, the egg white may turn pink, the yolk may remain intact, and the egg will not have an unusual odor."

Mr. Thien also assessed that faking eggs or injecting chemicals into eggs is unlikely, as sellers have no economic incentive to do so. "The price of an egg is not high, and eggs with unusual colors don't have a higher economic value than regular eggs. Adding chemicals to eggs would be very expensive, and sellers would gain virtually no economic benefit."

With over 10 years of experience raising and selling poultry eggs, Ms. Chu, a small trader in Thai Binh, said she had encountered similar situations regarding duck eggs with unusually shaped egg whites. According to Ms. Chu, normally, these eggs would have egg whites that are slightly pinkish in color.

"Even from the outside, using traditional methods like examining them under a light, it's impossible to detect eggs with such abnormal egg whites. These could be eggs that have been stored for a long time in a humid, anaerobic environment, causing the egg whites to change color while the yolks remain intact."

Previously, on April 17th, Ms. NT D., residing in Quyet Thang Hamlet, Hoa Hieu Ward, Thai Hoa Town, Nghe An Province, purchased 10 fertilized duck eggs at Hieu Market for her family's meal. However, after boiling them, she discovered that some of the eggs had an unusual color; upon peeling them, they were a reddish-pink color and emitted a strong, foul odor.

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