Why Does Mayonnaise Split?

Mayonnaise splits when the emulsion formed by the oil and egg yolk breaks down. The most common causes are adding the oil too quickly or using ingredients at different temperatures. When mayonnaise splits, it loses its smooth, creamy texture, and the oil and water phases separate, leaving a lumpy mixture. Mayonnaise is an unstable emulsion: natural compounds in the egg yolk keep oil droplets suspended in the water phase. If the oil is poured in too quickly, these compounds cannot coat all the droplets, and the emulsion collapses. Differences in ingredient temperature also make it harder for the oil to disperse evenly, so bringing all the ingredients to room temperature is recommended.

How Can You Fix Split Mayonnaise?

Split mayonnaise can often be brought back together with the right technique. Work patiently and add the mixture slowly to avoid splitting it again.

Whisk 1 egg yolk in a clean bowl. Slowly add the split mayonnaise to the yolk in a thin stream. Whisk until smooth after each addition. Instead of egg, you can also use one 5 ml measure of warm water or mustard to bring the mixture back together.

What Mistakes Are Common When Making Mayonnaise?

A few common mistakes increase the risk of splitting. Most are directly related to ingredient temperature and how quickly the oil is added.

Pouring in all the oil at once can prevent the emulsion from forming. Using cold eggs straight from the refrigerator makes it harder for the oil to blend evenly. Whisking too slowly or inconsistently weakens the emulsion. Adding too much oil for the amount of egg yolk throws off the balance.

What Are the Best Ingredients for Mayonnaise?

Fresh egg, room-temperature oil, and a small amount of an acidic liquid, such as lemon juice or vinegar, are enough for homemade mayonnaise. Adding a small amount of acid right at the beginning helps the emulsion form more evenly.

Which Oil Should You Use for Mayonnaise?

Neutral-tasting oils such as sunflower or canola oil are generally preferred because they help the emulsion form without overpowering the flavor. If you use olive oil, make it only a small portion of the total oil and use a neutral oil for the rest. Oil at room temperature helps the emulsion form more evenly than cold oil.

How Can You Prevent Mayonnaise from Splitting?

A few simple habits can help prevent mayonnaise from splitting. Pour the oil into the mixing bowl slowly, in a thin stream; a blender or food processor can make it easier to control the flow. Choosing a more neutral-tasting oil instead of olive oil can also help the emulsion remain stable. Olive oil's strong flavor can make the mixture bitter and less stable when used in large amounts.

Homemade mayonnaise contains raw egg, so eat it shortly after preparation and keep it refrigerated. Using pasteurized eggs reduces the risk of Salmonella; pregnant women, young children, older adults, and people with weakened immune systems should eat raw-egg mayonnaise only if it is made with pasteurized eggs. Mayonnaise splits when the emulsion does not form properly; adding the oil slowly and keeping the ingredients at room temperature greatly reduces the risk. If it splits, slowly whisking it into 1 fresh egg yolk is often enough to bring it back together. Following this method patiently and in the right order is the most reliable way to make homemade mayonnaise without splitting it.