The Guide to Sous Vide Eggs

Let's start off by saying that despite the title of this post, sous-vide eggs are a misnomer. "Slow-cooked eggs" would be a more apt description. Very, very slow-cooked eggs even better. It's only through association with the equipment used to cook sous-vide (vacuum-sealed) foods that the term sous-vide eggs has stuck, despite the fact that there is no vacuum involved in their preparation. Still, it's the common term for them, so I'll use it.

With that out of the way, let's get cracking with the matter at hand. Sous-vide eggs made their way around pretty much every fancy restaurant's menu in some form or another between five and ten years ago. It's one of the easiest and best uses of a sous-vide style water circulator—it required no expensive vacuum sealer (the eggs cook directly in their shells), and it allowed chefs to achieve textures with eggs that they had never been able to achieve before.

We recently reviewed the best immersion circulators on the market for home cooks, so the time is ripe for you to get in on the action. Today we're going to talk about the ins and outs of cooking eggs in the shell in a water bath.

Consider the Egg and Its Components

While we generally think of eggs as having two parts—the white and the yolk—there are actually three phases that we should care about: the yolk, the tight white, and the loose white. (McGee, On Food and Cooking, pg 75-78)

The yolk is the main nutrient source for the developing chicken embryo, and as such contains most of the nutritive value in the egg, including vitamins, minerals, and a good chunk of fat and protein. It's tightly bound in a membrane that keeps it spherical within the egg (though it flattens out and spreads when you break the egg onto a plate or in a pan.

The tight white consists of about 90 percent water with the rest being made up of proteins and a minute amount of minerals, fatty acids, and glucose. It is contained within a delicate membrane that is just slightly smaller than the full size of the egg.

Finally, the loose white is the part of the egg white that is not contained by the egg white membrane. When you crack the egg open, it's the white that spreads freely away from the rest of the egg. Its composition is similar to that of the tight white, but it has a lower concentration of proteins and other dissolved solids.

As eggs age, both the yolk and the tight white membranes will get thinner and more fragile. At the same time, the tight white will leak moisture into the loose white, diluting the loose white further and causing it to become even runnier.

Raw eggs are basically balloons of water thickened up by proteins. In their raw state, these proteins are tightly and individually packed and can thus flow relatively freely around each other. Think of them as little balls of yarn. As the egg gets heated, these balls slowly loosen up. Eventually, they begin to entangle one another, creating a semi-solid meshwork that is powerful enough to suspend the water, fat, and minerals that make up the rest of the egg.

Keep on cooking and that mesh will start to tighten up, eventually squeezing so tight that emulsions will break and the egg—in particular the egg yolk—will go from being tender and homogenous to dry and crumbly.

Why is this important for sous-vide cooking? Because of varying concentrations of different types of proteins within each of the eggs' three consituent parts, each of those parts behaves slightly differently when heated. Tight whites will begin to set first, though they don't become fully firm until a relatively high temperature. Loose whites remain watery until high temperatures, and yolks fall in the middle, gelling softy at moderate temperatures and getting firmer and firmer the more you heat them.

Here's What Happens to Sous-Vide Eggs at Different Temperatures

To demonstrate this, I cooked eggs in a sous-vide cooker to various temperatures ranging from 130°F (54.4°C) to 165°F (73.9°C)*. In each case, I heated large eggs for exactly 40 minutes—enough time for the egg to reach thermal equilibrium (that is, it is the same temperature as the water bath all the way through to the center), but not so long that the effects of prolonged cooking will have started to take effect. (We'll discuss those effects more later on.)

*Note that my sous-vide cooker has temp-set resolution of 1°F or 0.1°C, hence the conflicting number of significant digits.

Sous-Vide Egg Cooked to 130°F (54.4°C)

At 130°F, an egg can sit indefinitely without any sort of gelling taking place. This is useful if you have a fear of using raw eggs in sauces like mayonnaise or Caesar salad dressing. By holding an egg at 130°F for a few hours, you can effectively sterilize it, making it safer to consume in raw preparations.

Loose white: Indistinguishable from raw.
Tight white: Indistinguishable from raw.
Yolk: Indistinguishable from raw.

Sous-Vide Egg Cooked to 135°F (57.2°C)

Proteins are just beginning to unravel, causing the egg white to take on a cloudy appearance. Texture-wise, it's tough to distinguish the egg from a raw egg.

Loose white: Appearance is slightly cloudy, texture is indistinguishable from raw.
Tight white: Appearance is slightly cloudy, texture is indistinguishable from raw.
Yolk: Indistinguishable from raw.

Sous-Vide Egg Cooked to 140°F (60°C)