The Science of A Perfect Soft-Boiled Egg

If you google “how to make a soft-boiled egg,” you might be led to believe that the process hinges entirely on timing. Some recipe authors even urge you to use a timer. The first clue that this approach doesn’t work is that they all tell you different cooking times. Is it something in the water?

In a way, yes. Cooking an egg is transferring heat to it via water. Before we propose a method for achieving the ideal soft-boiled egg, let’s first clarify the goal: what constitutes a perfect soft-boiled egg?

This is the definition we will use: it should have a soft, gel-like egg white with a mostly runny egg yolk. The white should be set but not rubbery. The yolk should be runny but not watery. Additionally, we must ensure that food safety is not compromised for the sake of texture. Even though the yolk remains runny, the risk of salmonella should be virtually nonexistent.

We will begin by examining the anatomy of an egg and how its various components respond to heat. Next, we will explore the two key modes of heat transfer involved in our cooking process. Finally, based on these insights, we will propose the optimal method for cooking a soft-boiled egg.