Given the price of eggs and ongoing shortages at the moment, it may be less important to consumers than usual whether an egg is white or brown, organic or not, or how dark the egg’s yolk is. We live in a world where thieves can swipe $40,000 worth of eggs from a single trailer and Trader Joe’s limits customers to one dozen eggs per day. But this too shall pass, and we can again ponder, what makes one egg yolk darker than another, and does it mean anything?
You’re likely familiar with those dark orange yolks common to fancy free-range and farmer’s market eggs. Some people love them, some find them unsettling, preferring the bright yellow of “regular” store-bought white eggs. There’s actually a wide range of yolk colors, from off-white to deep red. At its core, there aren’t a lot of differences among the various shades beyond color: The nutritional value is the same, flavor differences may be perceived, but haven’t been clinically proven (though there is evidence of flavor differences between the eggs from different chicken breeds). In fact, the color of the egg yolk is heavily influenced by a chicken’s diet, along with the age of the hen and other environmental factors. What’s more, a yolk’s color might be a clue to additional details, like access to free-range grazing and the overall quality of life an egg-laying chicken experiences.
Yolk color is influenced primarily by diet
In 1915, an agricultural scientist named Leroy Palmer demonstrated that the color of egg yolks are influenced by the consumption or absence of foods rich in carotenoids, specifically a class of carotenoids called xanthophylls. These are plant pigments that impact an animal’s (and an egg’s) color when eaten (for example, eating too many carrots can turn a person’s skin orange). These yellow, orange, and red pigments are common in the plants that hens eat, particularly when they’re grazing outdoors. The proteins from munching bugs and grubs also affects color.
The diet of free-range chickens is less consistent than caged animals, so yolk colors will vary from clutch to clutch, and chicken to chicken. In general, pale yellow yolks indicate more corn or wheat in a chicken’s diet. Chickens eating fresh grass, clover and other greens produce brighter, deeper yellow yolks. Rich, deep orange yolks often come from a diet supplemented with marigolds (provided by the farmer), or indicate a chicken foraging for most of its food, eating a wide variety of plants and bugs. Red yolks can come from adding chili peppers to the feed.
These factors are a big deal for farmers. Consumers expect consistency, and it turns out yolk color preferences may be regional. While northern Europeans, for example, tend to prefer pale yellow yolks, people in the Mediterranean go for deep orange-red yolks. There’s a measuring tool called a DSM yolk color fan to help farmers seeking desired shades.
Does yolk color indicate quality or freshness?
As an egg grows stale, the white or albumin may break down and become more watery, but the yolk will stay the same color. If you want to check if an egg is getting out of date or spoiled, employ a simple float test instead. If it floats in water, it’s time to buy fresh eggs.
While a yolk’s color doesn’t speak directly to the quality of an egg, there are some clues to be gleaned from both its shade and brightness or paleness. The lighter in color and the less “rich” that color, the more corn or other grains the bird’s been fed, likely in a controlled (caged) environment. Deep yellow and orange yolks with a brightness to them are an indicator chickens are free to graze and forage out in the open. It may also reflect the season eggs were harvested: chickens feed outside more during warmer weather with plenty of plant growth.
There’s also some evidence that as a hen ages, it may produce darker yolks. However that natural tendency may be countered by an increasingly grain-heavy diet as grazing habits change, making for lighter yolks. Hens are also sensitive to temperature and weather changes, which may impact yolk color. No matter the yolk’s color, the hen is being well fed. In addition to grains, grass, or bugs, hens are given supplementary feed to ensure they get a good balance of necessary nutrients and minerals.
