What Are Egg yolks and How Can I Use Them?

Here's everything worth knowing about egg yolks and how to pick them, what they are, how to store them, and what to use instead, plus 1,712 recipes to cook tonight.

Key Points

The yolk holds the egg's fat, fat-soluble vitamins, and the emulsifier lecithin that powers mayonnaise and hollandaise.
One yolk suspends about ¾ cup of oil and thickens custards and pastry cream as it heats.
Yolks scramble above roughly 160°F (70°C); temper with hot liquid and never boil a custard.
For thickening only, swap a cornstarch slurry, about 1 tablespoon per cup of liquid, losing the richness.
Store leftover yolks under a film of cold water and use within 2 days, or freeze with salt or sugar.

What are egg yolks?

The yolk is the rich, golden center of the egg. It carries almost everything that makes eggs valuable in the kitchen beyond plain protein: the fat, the fat-soluble vitamins (A, D, E, and K), and the natural emulsifier lecithin that lets oil and water bind into a smooth sauce.

A large yolk is about 33% of the egg's liquid weight and roughly 55 calories, most of it fat. That fat is the point: it is what gives custards their silk and rich doughs their tenderness.

For the basics of buying and storing eggs, see the eggs hub. This page is about what the yolk does on its own.

What the Yolk Does

Lecithin in the yolk is one of the most effective emulsifiers a home cook has. A single yolk will hold around ¾ cup of oil in suspension, which is the whole mechanism behind mayonnaise and hollandaise.

Yolks are also a thickener. As they heat, their proteins set and grip liquid, turning milk and cream into pourable custard, pastry cream, or an ice cream base. A classic Crema Pasticcera / Custard Cream leans entirely on this.

In baking, extra yolks mean a softer crumb and deeper color, which is why a Napolean Cake calls for them by the handful.

Cooking and Pairing

The thing that goes wrong with yolks is heat. They begin to thicken around 150°F (65°C) and scramble into grainy curds above roughly 160°F (70°C), so a custard taken too hot turns to sweet scrambled egg.

The fix is tempering. Whisk a little of the hot liquid into the yolks first to warm them gently, then return that mixture to the pot, and never let it boil. A custard like Crystal Vanilla Bean Crème Brûlée lives or dies on this step.

Yolks pair naturally with cream, butter, sugar, vanilla, and savory partners like lemon and stock. Keep acid and salt off raw yolks until you are ready to whisk, since both will start to "cook" and pit the surface if they sit.

Substitutes

No swap fully replaces a yolk, because each job it does is different.

If a recipe wants yolks purely to thicken, a slurry of cornstarch (about 1 tablespoon per cup of liquid) will set the liquid, though without the richness or color. For emulsifying, prepared mustard or a spoonful of lecithin can stabilize a dressing in place of yolk.

For binding in baking you lose the most: nothing clean brings back the fat and color a yolk adds. Leftover whites are the natural counterpart, so plan a meringue or an angel food cake when a recipe leaves you with extras.

Storing Leftover Yolks

Separated yolks dry out fast because there is no white protecting them. Slip them into a small container, pour a thin film of cold water over the top to keep a skin from forming, then cover and refrigerate.

Use them within 2 days. They also freeze, but raw yolks gel when frozen, so whisk in a pinch of salt (for savory use) or a little sugar (for sweet) before freezing to keep them pourable when thawed.