How to Boil an Egg? Scientists Claim to Have Cracked the Recipe.

A colleague approached Ernesto Di Maio, a materials scientist in Naples, Italy, and an expert in plastic foams, with a blunt suggestion: “You should do something cooler.” The colleague had a project in mind, Dr. Di Maio recalled. He wanted a perfectly boiled egg.

The task was harder than it might seem, as many home cooks know. The yolk and the egg white, or albumen, have different chemical compositions, which call for different heating temperatures. Dr. Di Maio and his colleagues also welcomed the chance to one-up the Michelin-star chef Carlo Cracco, an egg evangelist who charges $52 for an egg yolk dish at his restaurant in Milan.

The scientists devised a way of cooking an egg that requires no special culinary skill or fancy gadgets. It took about 300 eggs, though the researchers “didn’t eat all of them,” said Pellegrino Musto, a polymer expert at the National Research Council of Italy.

The researchers said their method, published on Thursday, preserves the distinct textures of the egg as well as its nutritional value.

The two parts of the egg require different cooking temperatures because they have different chemical components. “The albumen is mainly composed of water and proteins,” said Emilia Di Lorenzo, a graduate student in Dr. Di Maio’s lab at the University of Naples Federico II who recently published a paper on foaming pizza. “Yolk, on the other hand, is much richer in nutrients.”

Hard-boiling an egg is a popular approach that calls for at least 10 minutes of immersion in boiling water. That is long enough for the yolk to be thoroughly cooked. But it’s also plenty of time for the albumen’s proteins to unfold and clump, expelling water molecules as they become heated. The approach can also create a green ring around the yolk, which indicates the presence of smelly ferrous sulfide.

“Many times people say that they don’t like the rubberiness of the egg white, or the graininess of the yolk in a hard-boiled egg,” said Nelson Serrano-Bahri, a chef and the director of innovation at the American Egg Board, the egg industry’s main trade association, which has lately been dealing with soaring prices and worries about the bird flu.

A soft boil, on the other hand, needs a much shorter cooking period. That keeps the albumen from turning hard — but may also keep the yolk too soft. Ms. Di Lorenzo explained that the yolk is rich in lipids which, when heated, become more fluid. Though some people prefer a runny yolk, others find it revolting.

A third method, known as sous vide, cooks an egg for an hour in a water bath of 150 degrees Fahrenheit. That’s the ideal temperature for the yolk, but the prolonged exposure is less optimal for the albumen because the water is not hot enough to denature its proteins.

Ms. Di Lorenzo was blunt about the sous vide approach: “It’s runny. I am not a big fan.”

The scientists’ new method, derived with the help of fluid dynamics software, calls for alternating between boiling and lukewarm water: The egg gets two minutes in 212-degree water, followed by two minutes at 86 degrees, with the cycle repeated eight times. Dr. Di Maio explained that the average temperature of the two immersions, 150 degrees, is ideal for the yolk, while the hotter bath is sufficient to cook the albumen.

“The very key of our method is to have a well-cooked albumen without wasting the yolk,” Dr. Di Maio said.

Relative to the other methods, the periodic baths did a better job of preserving the egg’s nutrients, the study found. The authors noted a higher concentration of polyphenols, compounds that protect against DNA damage.

“It’s probably brilliant — but who is the method for?” asked Deb Perelman, who runs the popular Smitten Kitchen blog. “For home cooking, there’s always a necessary balance of perfect versus a reasonable effort.”

Her preferred foolproof method involves a long ice bath after the egg is cooked. In a recipe for The New York Times, J. Kenji López-Alt proposed steaming the egg in a single inch of water.

“It’s a matter of taste,” Ms. Di Lorenzo said. If science is universal, food is deeply personal. Some people even eat raw eggs.

There is one big drawback to the new Italian technique. “It’s more difficult to peel the periodic egg because everything is softer,” Dr. Di Maio said.

But Mr. Serrano-Bahri said that the Egg Board was on the case. “We are running a study to figure out that,” he said. “I could have an answer for you in the coming months.”