What you see: Chalky white coloring on top of your brown egg.
What it is: A spot the chicken missed when she was adding pigment to her eggs.
Eat or toss: Eat! This egg is fine.
Patchy white areas on brown eggs
While it might look like this egg got dusted with some kind of powder, the issue here is actually that something is missing.
Eggshells are made of calcium carbonate, a form of calcium that you also find in oyster shells, limestone and chalk. It’s white, just like many eggs. Some chicken feed even includes ground up oyster shells to make sure chickens get the calcium carbonate needed for their eggs.
Chickens that produce brown eggs add pigment at the end of the egg-making process, so the exterior is brown, but the shells still look white on the inside.
So if you see a brown egg with what looks like a white powdery dusting, you’re looking at an egg whose chicken simply missed some spots when it came to painting her egg. Possibly that portion of the egg had a slightly rougher texture, which made it harder to get an even coat.
“There’s nothing wrong with it,” said Deana R. Jones, director of the U.S. National Poultry Research Center.
Chickens make eggs in what’s literally called a shell gland. For a tour of what that looks like, check out Auburn University’s Virtual Chicken video. Here’s how they describe the shell-making process, which occurs after the yolk, white and membranes have formed:
“…a highly concentrated solution of calcium carbonate is secreted by the shell gland and crystals of calcite form and grow on the outer shell membrane. As the crystals expand they grow into one another to form a solid shell. Very tiny spaces left in between the crystals leave pores in the shell.”
Calcite, for what it’s worth, is a form of calcium carbonate. In a brown-egg-laying chicken, the next step is to apply the pigment.
SOURCES:
- Deana R. Jones. Center Director, U.S. National Poultry Research Center. U.S. Department of Agriculture, Agricultural Research Service.
- How Do Chickens Lay Eggs? Understanding Your Egg-Laying Chickens. Patrick Biggs, Ph.D. Purina Mills. Accessed November 2024.
- Nutritionist, Companion Animal Technical Solutions. Purina Mills. Accessed November 2024.
- Virtual Chicken Auburn University. Department of Poultry Science. Accessed via YouTube November 2024.
- National Center for Biotechnology Information (2024). PubChem Compound Summary for CID 10112, Calcium Carbonate. Retrieved November 14, 2024.
- Calcite. Mineral. R.V. Dietrich. Britannica. Last Updated Oct. 10, 2024. Accessed November 2024.
