Science's Easter Egg Hunt: What Makes an Eggshell Crack?

With Easter Sunday just days away, children across the country will be on the hunt for eggs—chocolate and chicken. Researchers, on the other hand, have been hunting for the secrets behind eggshells. These shells—delicate but strong—could help scientists create new kinds of tiny structures.

So, what makes the humble egg crack?

Scientists from the United States, Canada, Germany and Spain have been working to solve the mystery. They discovered a particular protein is key to understanding, and reproducing, eggshells, according to research published this week in Science Advances.

Eggs are lined up at a poultry farm in the settlement of Novozavedennoye in Russia’s Stavropol region, on August 24, 2017. Researchers found a protein that could have big implications for the food industry. Eduard Korniyenko/Reuters

Eggs, it turns out, are pretty special.

"The shell is remarkably strong and tough to serve its function," Marc McKee, a professor of mineralized tissue cell biology at McGill University, Quebec, told Newsweek.

Yet, over time, the shell becomes thinner and weaker, making it easier for chicks to crack their way out.

The structures are also remarkable for their rapid formation.

"A laying hen forms a 0.2-oz eggshell in about 17 hours almost every day," said McKee, who is one of the study authors. That makes them one of the fastest known mineral systems produced by a living organism. McKee has been studying the incredible vessels for well over a decade.

Advances in imaging have allowed McKee and his team to uncover their secrets. Researchers cut a very thin slice of eggshell and imaged its internal structure. They used a powerful microscope to look all the way down to the atomic crystal planes of the eggshell's mineral nanostructure, McKee said.

3_29_Monkeys Eggs
Black-capped squirrel monkeys eat food hidden in painted papier-mâché eggshells at London Zoo, on March 29. Researchers believe that lightweight but strong nanomaterials like their recreated eggshell are revolutionizing everything from electronics to healthcare. Toby Melville/Reuters

The team found different amounts of a protein called osteopontin in different layers of the shell. The harder the layer, the higher the concentration of osteopontin. This protein, they thought, might be behind an eggshell's changing strength.

To test this theory, the researchers grew these same mineral crystals in the presence of osteopontin. Again, they found that higher osteopontin concentrations led to harder shells. The protein, it seems, is critically important for an eggshell's structure.

Related: An extraordinary egg has been found that has left experts baffled

The researchers think their work could impact numerous industries. Lightweight but strong nanomaterials like their recreated eggshell are revolutionizing everything from electronics to healthcare.

Learning more about the shell's structure, McKee said, could even improve eggs themselves. Weaknesses and holes can leave eggs open to contamination. Working out what makes them crack—or not—can help the food industry breed more of those hens that produce the strongest eggs.