When hens eat feed containing yellow corn or alfalfa meal, they lay eggs with medium-yellow yolks. When they eat wheat or barley, they lay eggs with lighter-colored yolks. A colorless diet, such as white cornmeal, produces nearly white egg yolks.
A diet rich in pigments will produce eggs with darker yolks. Hens consuming yellow corn or alfalfa meal will lay eggs with medium-yellow yolks, while those on a diet of wheat or barley tend to lay the eggs with the lightest-coloured yolks.
As you suspected, the reason Americans eggs tend to have bright yellow yolks has nothing to do with "hormones" but rather with what we feed our hens. Beyer says egg yolk color is almost entirely influenced by the birds' diet. So if you're feeding birds yellow corn, "it gets in the egg," he explains.
But I can assure you, that there is a difference in colour of egg yolks within Europe. Southern Europeans prefer their egg yolks to be more orange, while Northern Europeans prefer them to be more yellow.
The Bottom Line. Don't freak out. The occasional, unexpected white yolk in your carton or eggs is just as edible and delicious as a yellow one.
When hens eat feed containing yellow corn or alfalfa meal, they lay eggs with medium-yellow yolks. When they eat wheat or barley, they lay eggs with lighter-colored yolks. A colorless diet, such as white cornmeal, produces nearly white egg yolks.
So what determines the color of the eggshell? White eggs in the United States are not bleached, contrary to popular internet belief. The color, instead, depends on the kind of chicken that is laying the egg, and it usually corresponds with the color of the chicken's earlobe.
In Europe, farms vaccinate chickens against salmonella. That means the cuticle is still intact when eggs are sold. Refrigerating eggs with the cuticle intact could actually cause mildew to grow. Which could cause… you guessed it salmonella contamination.
The shade of an egg yolk is completely determined by the hen's diet. Hens that are given feed full of yellow-orange pigments will lay eggs with darker yolks. It's as simple as that! No artificial coloring is allowed in chicken feed, but some farmers will add marigold petals to give yolks an orangey color boost.
American farms wash eggs to strip the cuticle, or outer protective layer, which prevents contamination outside the shell. Without the cuticle, eggs must be refrigerated to combat bacterial infection from inside. In Europe, it's illegal to wash eggs and instead, farms vaccinate chickens against salmonella.
While egg yolk's shade may not impact its health value, many chefs, farmers and home cooks swear that the yolk's color does actually affect the flavor of the egg — and the dish it's used in. The more vibrant the shade, the more vibrant the taste, they say.
But according to TODAY, darker egg yolks are not actually more nutritious. They just look different because of the hen's diet. According to the USDA, egg nutrition is basically the same, regardless of yolk color. Eggs have the same amount of protein and fat and contain the same vitamins and minerals.
White is the most in-demand eggshell color in America. Christopher Columbus is believed to have brought the most famous white-egg — the Single-Comb White Leghorn — to America in 1493. It's thought that Leghorns originated in Italy.
It's not a natural trait of a fancy European breed of hen or a sign of overly pampered birds. The yolk color actually comes from what the hens eat: a diet rich in carotenoids, the natural yellow-orange pigment found in fruits (cantaloupe), vegetables (carrots, sweet potatoes, and kale), and flowers.
It's as simple as that! No artificial coloring is allowed in chicken feed, but some farmers will add marigold petals to give egg yolks an orangey color boost. Reddish yolks are made possible by adding capsicum (i.e. red bell peppers) to chicken feed, and throwing in a dash of paprika can have the same effect.
In general, people in northern Europe prefer lighter, paler yellow yolks, while southern Europeans look for a golden color, and the Mediterranean region almost exclusively eats eggs with orange-red yolks.
According to Swan, “salmonella isn't as common in Europe1 [as in the US2, and] hens may be vaccinated against salmonella.” Plus, eggs aren't cleaned with water so the protective coating stays intact, lowering the chances of salmonella entering the egg.
“An orange yolk is indicative of the chicken's diet,” says Steele. “So if the chicken is eating a lot of things that have xanthophylls in them, which is beta-carotene, it makes egg yolks orange.” This pigment is in foods like marigold, alfalfa, pumpkin, and a lot of leafy greens.
Italian eggs are gently wiped clean from debris before they're packaged and ready for sale, but never washed. Because they have this protective outer layer they don't need to be refrigerated and can stay at room temperature for a week or two without any deleterious effect.
The different storage conditions are a result of the way that eggs are farmed and processed in the US compared with in the UK and other European nations. In the US, to reduce the risk of salmonella infection, eggs are washed and sprayed with a chemical sanitiser before they are sold to the public.
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.
Differences in egg cleanliness standards. In the US eggs must be washed before being sold to ensure they are clean. In the UK they must not be washed, to ensure they are clean. Meaning that US eggs can't be sold in the UK, and vice versa.
Eggs in the US are required to be power washed, to remove fecal matter. Eggs in Europe are forbidden to be power-washed, to preserve the anti-bacteria coating on them. Thus, US eggs look whiter (assuming they are white).
One basic, important food that the English do right is eggs. English eggs look and taste very different from American ones. The yolks are more orange and they taste slightly richer. They also taste fresher and more flavorful than your average American factory farm egg.