The Principles Of Emulsification

Let's start by explaining what an emulsification is and how it relates to cooking. An emulsification is a mixture of two or more liquids that normally wouldn't mix. Think oil and water. This is done through the use of a binder or an emulsifier. In cooking, this could be mustard in any form or egg yolk.

Jump to:

• How to Build a Simple Vinaigrette
• Other Emulsifications

Common items that are emulsifications include any well-made salad dressing, mayonnaise, hollandaise sauce, hot dogs, chocolate, homogenized milk, and butter. All of these items contain at least two substances that don't mix naturally. They are held together with either an added stabilizer or by a stabilizing process. I find that emulsifications are a pretty good place to start when teaching cooking. The concept of an emulsion is pretty complex and even explaining the process at times can be difficult. However, the actual application of the emulsion technique, when simplified to its most basic processes, is much less daunting than one might expect.

How to Build a Simple Vinaigrette

A vinaigrette is an emulsion of oil and vinegar. This is generally accomplished with the use of mustard as the binder. It is actually a protein or string of proteins in the mustard called lecithin, not the mustard itself, that binds the two liquids. This same string of proteins is found in egg yolks and soybeans. So you have oil, vinegar, and lecithin in a bowl but the emulsion breaks. What happened? If you have ever made a salad dressing or otherwise mixed oil and vinegar it is likely that the two liquids have separated. If you looked at it through a glass jar you would be able to see the oil floating on top of the vinegar or water. This is a separation of the two liquids. In terms of an emulsification, we refer to this as breaking or splitting. When an emulsion is properly formed it will hold together for a very long time. There are two main things to think about when building an oil and vinegar emulsification.

1. The Ratio of Oil to Vinegar

Generally, for a basic vinaigrette, a ratio of 3 parts oil to 1 part vinegar will create a nice texture and a slight tartness. For a thicker vinaigrette, a ratio of 4 parts oil to 1 part vinegar can be made. The extra oil causes a thicker dressing, which may seem counterintuitive. But because more oil droplets are suspended and dispersed throughout the vinegar, the dressing gets a thicker, creamier texture. Imagine a room ¾ full of coloured plastic balls. This room illustrates a standard 3:1 ratio. It's a lot of balls. It is difficult to move around but not impossible. Now imagine the same room but so full of plastic balls that you couldn't fit one more in. It would be much more difficult, if not impossible, to move around. This second example illustrates a 4:1 ratio. The more oil you add, the thicker the dressing will get. For a deeper dive into vinaigrettes and their many variations, check out my guide to everything I know about vinaigrette.

2. The Process of Making the Emulsion

A strong emulsion is one that is made slowly. Imagine the room from the above example. If you tried to fill the room with all the plastic balls at once it wouldn't work. You would never be able to get them all through the door. You have to fill the room with a few plastic balls at a time. The same principle is true of building an emulsification. The first step in the process is to mix the vinegar with the binder. Imagining that we want about 1 cup of vinaigrette, we would mix ¼ cup of vinegar with 1 teaspoon of mustard powder. The next step is to take our ¾ cup oil and mix it into the vinegar and mustard. But, as we know from the plastic ball in the room example, we can't just pour all of the oil in and build a stable emulsification. We have to start slowly. While whisking, we pour a few drops of oil into the vinegar and mustard mixture. We whisk until the oil has been fully incorporated into the vinegar. We know this has happened because there are no visible sheen or oil droplets. Once this first amount of oil is emulsified we add a bit more oil. We continue this process until all of the oil has been incorporated.

Troubleshooting a Broken Emulsion

Even experienced cooks break emulsions from time to time. If your vinaigrette splits, don't throw it out. Here are a few ways to fix it:

• Start fresh with the binder -- Put a small amount of mustard or egg yolk in a clean bowl and slowly whisk the broken emulsion into it, just as if the broken mixture were your oil.
• Add a splash of warm water -- Sometimes a small amount of warm water whisked in vigorously can help re-emulsify a dressing that has just started to break.
• Use a blender -- If whisking by hand isn't working, pour the broken emulsion into a blender and blitz it. The high speed forces the droplets back together.

The most common reasons an emulsion breaks are adding the oil too quickly, not whisking vigorously enough, or having ingredients at very different temperatures.

Other Emulsifications

The above process is pretty much the same for any type of emulsion. Let's look at mayonnaise. In mayonnaise, the emulsion is bound by lecithin in the egg yolk. As a backup there is often a bit of mustard added as well, though this is mostly unnecessary. For the mayonnaise, we are going to use a ratio of 1:1 for the egg to oil and 4:1 for the oil to vinegar. This is 1 egg yolk, 1 cup of oil, and ¼ cup of acid which may be just vinegar, just lemon juice, or a combination of the two. Just like with the vinaigrette we start by mixing the egg yolk (the binder) with the vinegar or acid. From there we slowly start to whisk in the oil a few drops at a time. The process is exactly the same for hollandaise sauce except the egg yolks are tempered with the vinegar (heated but not to the point of cooking) and clarified butter is used rather than oil.

Emulsions in Everyday Cooking

Understanding emulsification isn't just useful for making dressings and sauces from scratch. This technique shows up everywhere in cooking. When you deglaze a pan and whisk in butter to make a pan sauce, you're building an emulsion. When you add pasta water to your carbonara, the starchy water helps emulsify the fat from the cheese and egg with the other liquids. Even a well-made gravy or sauce relies on the same basic principles. Once you understand the mechanics of emulsification -- the slow addition, the constant whisking, and the role of the binder -- you'll find it easier to troubleshoot problems across a huge range of recipes. It's one of those foundational skills that quietly makes everything you cook just a little bit better.