Eating eggs with white yolks is completely safe, and scientists have explained the reason behind their unusual appearance.
Earlier this month, white-yolked eggs became a sensation on Japanese social media, raising questions about their safety. However, studies show that the color of egg yolks can vary widely depending on the diet of the hens.
Images and videos shared online showcase dishes made from eggs with completely white yolks, such as hard-boiled eggs or omelets. This unique coloration results from feeding the hens a rice-based diet instead of the typical corn-based feed, according to a study by the Institute of Advanced Biosciences at Keio University, published in Food Chemistry in October 2020.
“Eggs from rice-fed hens have a different aroma and texture compared to regular eggs,” the study notes. While standard eggs are known to be rich in vitamins B2, B12, and D, as well as minerals like calcium and iron, the study found that rice-fed eggs contain higher levels of betaine and uridine monophosphate. Betaine aids digestion and has anti-inflammatory properties, while uridine monophosphate supports the nervous system. Consuming white-yolked eggs is completely safe.
The color of the yolk is determined by the presence of pigments in the hens’ diet, primarily carotenoids. The amount of these pigments influences the intensity of the yolk’s color, ranging from pale yellow to deep orange, according to a 2011 study in Improving the Safety and Quality of Eggs and Egg Products. This finding is supported by a 2020 study published in Animal Feed Science and Technology.
Carotenoids are fat-soluble organic compounds found naturally in plants, fungi, animals, and microorganisms. They are categorized into two main groups: carotenes (red pigments) and xanthophylls, which are oxygenated derivatives of carotenes (yellow pigments). These compounds are known for their strong antioxidant properties.
A less common yolk color is light green, which can appear in hard-boiled eggs due to a reaction between iron and sulfur compounds. This discoloration is caused by overcooking but is safe to eat.
Green Eggs
In 2020, vivid green yolks from eggs produced on a farm in Malappuram, Kerala, India, attracted the attention of scientists and local media. Researchers from Kerala Veterinary and Animal Sciences University (KVASU) investigated and linked the unusual color to the hens’ diet. However, they were unable to pinpoint the exact cause, as the chickens were free-range. According to the farm owner, chicks hatched from these eggs also produced green-yolked eggs. He assured that the eggs are safe to eat, as his family regularly consumes them, noting that they taste just like regular eggs.
