oil droplets on water

Don’t Let Your Food Separate: Choosing & Using Emulsifiers

No matter how long you mix or whisk olive oil and balsamic vinegar, they will separate again shortly after you stop mixing. The same happens to that coconut oil + sugar syrup mixture for a vegan whipped cream, or mayonnaise with insufficient oil.

Water and oil don’t mix, it’s an unstable emulsion, and that poses a challenge for product developers. Salad dressings split, and caramels turn oily. It puts consumers off, the products don’t look appealing and won’t get bought.

To prevent the separation you can use emulsifiers. In this quick guide, we’ll give you some tips on choosing and using emulsifiers to make those appealing emulsified products you’re looking for.

Emulsifiers stabilize emulsions

Once you add some mustard to a mixture of oil and balsamic vinegar, they no longer split as quickly. Same when you add some lecithin to a caramel mixture, you no longer risk an oily surface. Lecithin and mustard act as emulsifiers. They stabilize the water and oil mixture by sitting on the intersection between water and oil.

How emulsifiers work: changing the surface

A mixture of water and oil is an emulsion. The two liquids don’t mix. Each liquid prefers to sit with its own kind. As such, droplets of water dispersed in oil will find each other. As a result, the two liquids separate.

An emulsifier prevents this from happening by ‘modifying the surface’ of the droplets. This ensures they don’t mind sitting within the other liquid as much anymore. As a result, they won’t separate at all, or less quickly.

oil droplets on water
Oil droplets lie on top of a sugar solution.

Emulsifiers sit in oil AND water

Emulsifiers sit on the interface between oil and water. By surrounding the individual droplets, they prevent the droplets from merging. Most emulsifiers can do this because of their special amphiphilic structure. Part of the emulsifier prefers to sit in water, the hydrophilic (water-loving) side. The other part prefers to sit in oil, the hydrophobic part. The emulsifier organizes itself such that the water loving side sits in the water and the hydrophobic part sits in the oil.

amphiphilic molecule
Example of an emulsifier in action. The emulsifier surrounds the oil droplet, stabilizing the emulsion.

Benefits of using emulsifiers in food

The main benefit of using an emulsifier is to stabilize a product that is made with an emulsion. Salad dressings are a common example, and emulsifier can stabilize the water and oil mixture for a long time.

But in doing so there are several side benefits that using emulsifiers enable.

Emulsifiers can aid fat reduction

Fats make a product creamy, rich, luscious. By taking out (part of) the fat, a product can become less appealing to consumers. But, with the fat the product might contain too many calories.

For various applications using an emulsion instead of a pure fat can provide a good solution. By incorporating some water into the fat, you can reduce the fat content, while still making a creamy product. Of course, you often need emulsifiers to stabilize this new fat-reduced product.

Emulsifiers can improve production stability

Even if an emulsion is stable in the final product packaging, it might not (yet) be so during production. Mixing, pumping, smearing, increased temperatures, it might all cause emulsions to split and separate during manufacturing. To make the product more robust in the production process, emulsifiers can help stabilize the product.

Product specific benefits

Even though at their core, emulsifiers help keep two liquids mixed, their application is broader than just pure emulsions:

  • Many baked goods such as contain emulsifiers to keep a moist crumb.
  • Foams often contain emulsifiers for proper aeration.
  • Ice cream contains emulsifiers to improve the freeze-thaw stability.
  • Chocolate contains lecithin to improve its flow properties (viscosity).
store bought tempered chocolate
Chocolate often contains lecithin or PGPR (polyglycerol polyricinoleate) to ensure it flows well while molten.

What to consider when choosing an emulsifier

There is a range of emulsifiers available for use in food. But, not every emulsifier will work for every emulsion. To select the most appropriate emulsifier, here are a few key considerations to keep in mind:

Does you product already contain (natural) emulsifiers?

There is a wide range of ingredients that naturally contain emulsifiers. One of the most common examples are egg yolks. Egg yolks contain lecithin, a commonly used emulsifier. As such, if your product already contains egg yolks, chances are, you need less or no emulsifiers at all. But, if you are trying to remove that egg yolk from your formula, you may need to find a new way to stabilize the product.

Are you making a W/O or O/W emulsion

Is your emulsion made of water droplets dispersed in oil, or do you have oil droplets dispersed in water? This is a key difference between emulsifiers and one that is crucial to know when choosing an emulsifier. Emulsifiers that stabilize a water-in-oil (W/O) emulsion will likely fail at stabilizing an oil-in-water (O/W) emulsion.

For stabilizing a W/O emulsion, generally speaking, the emulsifier should have a larger hydrophobic area. That is, most of the emulsifier prefers to sit in oil. The opposite is true for an O/W emulsion, you’d need an emulsifier with a preference for water.

HLB value

Manufacturers quantify the love for water vs. oil with an HLB value. Emulsifiers with a higher value prefer to sit in water. It’s why emulsifiers with an HLB value of 8-16 are best for an O/W emulsion. Lower HLB values of 3-7 are emulsifiers that work best in a W/O emulsion.

That said, the exact required number strongly depends on the emulsifier itself and the exact ingredients in your product.

amphiphilic emulsifiers in action

Your processing conditions

Not every emulsfiers works well at high (or low) temperatures. Some can handle shear better than others. As such, test your emulsifier under the conditions that you’ll actually be using the emulsifier. It may have worked well in the lab at room temperature, but not work well anymore in production where temperatures exceed 70°C.


Using emulsifiers in food is regulated in most countries globally. You’ll generally find limitations on the use of specific types of emulsifiers in various food products. Also, you might be limited in the quantity you’re allowed to use in your product. Always keep the relevant legislation in mind when developing your product and process.

Types of emulsifiers in food

A common way to group emulsifiers is by their origin: natural vs. synthetic. Natural emulsifiers would be the ones you’d naturall find in nature, such as the lecithin in egg yolk. Synthetic emulsifiers have been made by us humans.

Even though this distinction can be useful, it’s also helpful to look at emulsifiers from a structural perspective. There are quite a lot of different types of molecules that can work as an emulsifier. Some may already be naturally present in your ingredients.


Proteins such as those in milk (e.g. caseins) can often serve as an emulsifier. Proteins are large complex molecules with hydrophobic and hydrophilic sections. By lying on the interface between oil and water, they can help stabilize.

Often, proteins by themselves might not be strong enough to stabilize an emulsion, though it strongly depends on the exact product. So, you’ll often find them being present alongside other emulsifiers.


This is one of the more commonly used emulsifiers in food. Partly because it is naturally present in egg yolks and soy. Lecithin is your stereotypical example of an emulsifier. Lecithin molecules have a hydrophilic head and a hydrophobic tail.

But keep in mind that even within the world of lecithin there are a lot of choices to make. Lecithins can be made from various sources aside from the soy and egg, e.g. sunflower. And depending on how the lecithins are processed they can behave differently. Exchanging one lecithin for another is definitely not a guarantee for success.

Mono- and diglycerides

You can find mono- and diglycerides in a wide range of products. Mono- and diglycerides are made from fats (triglycerides). They also have a ‘classic’ hydrophobic tail and smaller hydrophilic head. They can be tuned to specific properties and as such there’s quite a wide range of them available.


Some small, well controlled particles can help stabilize an emulsion. They don’t necessarily have as distinct hydrophobic and hydrophilic regions, but their size and shape can still cause them to sit on the interface between water and oil. Emulsions stabilized this way are often referred to as puckering emulsions. This is a relatively newer area of research and not used as much in practical food applications as the others.

egg yolks
Egg yolks, naturally packed with emulsifiers.

Using & choosing emulsifiers

Mixtures of water and oil are naturally unstable. But, a stable emulsion can make a wide range of delicious (healthier) products. As such, you need to know how to stabilize an emulsion.

One way to stabilize an emulsion is by adding an emulsifier. The emulsifier prevents or slows down the separation of water and oil by sitting on the interface of these two liquids. To choose the right emulsifier you need to know what product you need to stabilize and whether you already have naturally occurring emulsifiers within.

With a well-chosen emulsifier you can develop and produce delicious foods containing both water and oil.

Not sure how to do this yourself? Let’s connect in a discovery call in which we’ll walk through your challenge.


Food Emulsifiers and Their Applications. Germany: Springer International Publishing, 2019, chapter 1

Morfo Zembyla,Brent S. Murray,Anwesha Sarkar, Water-in-oil emulsions stabilized by surfactants, biopolymers and/or particles: a review, Trends in Food Science & Technology, Oct-2020, link

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