What is an Emulsion? The Secret to Sauces and Dressings


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Understanding what is an emulsion and how to create one is essential in cooking. Using the proper mixing technique and emulsifier will ensure success in making stable sauces and dressings.

Different types of emulsions in clear jars.

Dressings and sauces are the culinary solutions to enhance flavors and complement other ingredients. Emulsified mixtures can come in different forms: hot, cold, savory, sweet, textured, or smooth. These simple add-ons help to elevate any dish without being the star of the plate. They can help add depth of flavor, texture, and moisture to make food more tantalizing.

Have you ever wondered what an emulsion is? It’s an essential cooking technique that’s easy to learn. Let’s take a closer look at how to use emulsions to create a vibrant and flavorful sauce or dressing.

Hand pouring oil into a mixing bowl.

What is an Emulsion?

The first thing I learned in my introductory food science class is that fat and water DO NOT mix, not a surprise. However, then the discussion led to why and how to combine them correctly for food applications. The solution is to create an emulsion!

An emulsion is a uniform mixture of two unmixable liquids like oil and water, using agitation from whisking or blending to create a uniform suspension. Depending on how the emulsion is formed, the agitation makes either small oil droplets or water/vinegar droplets. The droplets are called the “dispersed phase,” while the liquid surrounding the droplets is called “the continuous phase.”

For example, balsamic vinaigrette is an oil-in-water emulsion, whereas butter is a water-in-oil emulsion.

Not all emulsions last forever. Over time, especially for oil-in-water emulsions, the oil droplets will want to coalesce and join back together to form a large oil layer on the surface, as seen in the photo below. However, there is a solution to help stabilize the suspension and prevent them from regrouping. Emulsifiers can create physical barriers around the droplets so they stay in a uniform emulsion.

Types of Emulsions

  • Temporary: Emulsions are brief suspensions like oils and vinegar dressings and vinaigrettes. They usually separate in under an hour since no emulsifier is used. The only agitation is whisking or blending.
  • Semi-permanent: Emulsion lasts hours, like hollandaise sauce, which contains eggs.
  • Permanent: Emulsion lasts multiple days, like mayonnaise-based sauces that contain eggs.
Two photos showing the difference between a separated dressing and mixed emulsion.

Emulsifying Agents

An emulsifier is an ingredient that can help immiscible components stay suspended, preventing the oil from regrouping together and floating to the top of the sauce or dressing. Emulsifiers are molecules that have the unique ability to attract water (hydrophilic) and oil (lipophilic), allowing them to coat the dispersed phase and keep it uniformly suspended in the continuous phase.

Emulsifying agents should be first added and mixed with the continuous phase (like vinegar) so they can coat the dispersed phase (like oil) as it’s being whisked to create a stable emulsion.

  • Lecithin: A robust and efficient emulsifier, lecithin is a phospholipid found in egg yolks and soy that encourages oil-in-water emulsions. The lecithin in one egg yolk can emulsify about 7 ounces of oil; any more, and you will visibly see the emulsion separate and thin out.
  • Cholesterol: The cholesterol in eggs encourages oil-in-water emulsions.
  • Mustard: Contains a complex polysaccharide component to aid in emulsification but is not as useful over long periods of time compared to lecithin.
  • Mayonnaise: The mixture already contains lecithin and is a stable emulsion, so a small amount can be added to promote a uniform suspension.
  • Honey: Honey helps to break apart fats that accumulate together, but not as effectively as lecithin.
Pouring dressing onto a green salad.

Types of Emulsion-Based Dressings & Sauces

  • Vinaigrette: A temporary emulsion made with oil and vinegar, often without an emulsifier. A typical ratio of 3 parts oil to 1 part acid is used. The amounts would need to be adjusted based on the type of oil, acid, and/or vinegar used.
  • Mayonnaise-based: A dressing that uses mayonnaise as the base with additional flavorings and liquids like dairy (buttermilk, sour cream, yogurt), acids (vinegar, lemon or lime juice), fruits (tomatoes, olives, berries), vegetables (celery, onions, carrots), condiments (mustard, seasonings, sweeteners, capers), and protein (eggs) for a permanent emulsion.
  • Emulsified Vinaigrette: Oil and vinegar vinaigrette are emulsified using whole eggs for a creamy permanent emulsion.
  • Hollandaise: A hot emulsified sauce using egg yolks and butter. Often topped over eggs benedict.

Jessica Gavin

I'm a culinary school graduate, cookbook author, and a mom who loves croissants! My passion is creating recipes and sharing the science behind cooking to help you gain confidence in the kitchen.

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13 Comments Leave a comment or review

  1. Patricia says

    Hi, I did a southwest Dressing but it’s very thick what can I add to make it more liquid without change the flavor?

  2. Jason C Ross says

    This is a great read! I wish you explain more about emulsions where butter and water are involved. Can you just whisk butter into water? This is in the context of cheese sauce. Will the cheese emulsify directly into pasta water?

    • Jessica Gavin says

      When I make a cheese sauce I typically make a roux with flour and butter, then whisk in the liquid to adjust the thickness.

  3. Alireza etemadyfar says

    I like to make sauces with vegetables, olives and oil, always with spices, but sometimes my sauce does not stick together and separates. What is the reason?

  4. Andres says

    What a valuable article. I am new in cooking. I am making peanut butter. Natural oil separates from the rest of the peanut butter ingredient. That is why I am interested in lecithin which according to this article is found in egg yolks and soy.

    1) Can I use directly egg yolks or soy to achieve the same effect of lecithin on emulsifying natural oil?
    2) If so, how long will the peanut butter stay with this emulsion agent without getting spoiled?
    2.1) If with egg yolk?
    2.2) What about if with lecithin?
    3) If I cannot use them directly, then is there a home remedy technique to extract lecithin from these?
    3.1) What are these?

    Thank you for considering my many questions?

    More power to you!

    • Jessica Gavin says

      I haven’t tried using sodium citrate before for gravy. I usually find that the starches in the flour help to prevent separation. However, I’ve seen recipes use 1/2 teaspoon for 2 cups of liquid and 4 tablespoons fat. What other ingredients are you planning to use in the gravy? I’d love to hear how it turns out!