What's Up With Blue and Green Eggs?
- Blue eggs are blue because of biliverdin-IX, a pigment that’s produced in cells lining a hen’s oviduct.
- Biliverdin-IX, like protoporphyrin-IX, the pigment in brown eggs, is made from an iron-containing chemical called heme that comes from broken-down red blood cells.
- Biliverdin-IX is added to the hard testa layer of the egg shell during egg formation, so a blue egg is blue all the way through and is blue on the inside of the shell.
- Chickens that lay green eggs incorporate both blue biliverdin-IX and brown protoporphyrin-IX into their eggshells. Since most or all of the brown pigment is in the bloom, the inside of a green eggshell is blue.
- The hue of green eggs will vary depending on how much brown pigment is present—they can run the gradient from light blue-green to a dark olive.
- While blue eggs are not uncommon in birds (think of robin’s eggs), they are a little unusual in chickens. All of the chicken breeds that lay blue eggs originated in or contain breeding stock from South America.
|Blue egg courtesy of Veronica the Easter Egger|
|A few of the blue/green egg-laying Hipster Hens|
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