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Combating Separation: How to Stabilize Food Emulsions

Water and oil don’t mix. Over time, they will separate.

Ice cream, dressings, custard, and ganache, they all contain water and oil. And they aren’t the only ones. Many foods contain and rely on the presence of both water and fat. And, you don’t want them to split. Not during storage, and definitely not during production either.

So, you need to stabilize the emulsion, the mixture of water and oil. Luckily, there are a few ways to do so. Here, we’ll highlight three possible routes to success.

Strategy 1: Stabilize the emulsion by thickening it

For a mixture of oil and water to separate, it needs to be able to physically separate. That is, the oil and water molecules need to be able to move around sufficiently. Water molecules need to be able to find each other and the same goes for the oil molecules. If the water and oil in your mixture can’t move, they can’t separate.

So, to slow down or even prevent separation of an emulsion of water and oil: thicken the emulsion.

Add thickeners to prevent separation

Many salad dressings are stabilized by adding thickeners to the dressing. The dressing is no longer as liquid and doesn’t pour and flow as easily anymore. But, it’s still sufficiently liquid to be squeezed from a bottle for instance.

Thickeners are molecules that cause the liquid to which they are added to thicken up. The viscosity of the liquid goes up. Common examples are starches such as (modified) corn or potato starch. When you make a roux, or Turkish delight, you’re effectively using starches to thicken your sauce or candy.

three types of chocolate mousse
Chocolate mousse remains light and airy because of the chocolate that sets as it cools down.

Solidify the oil

Strictly said, once the oil in an emulsion has turned solid, the water and oil mixture no longer is an emulsion. An emulsion consists of two liquids. But, solidifying the fat is a sound strategy to stabilize a mixture of water and fat.

Once the fat has set, the water can no longer move through anymore. It’s locked in place. A lot of dishes made with chocolate are stabilized this way. A ganache and chocolate mousse are both stable because of the presence of solidified chocolate. The same applies to butter, which is an emulsion of water and butter fat.

You can either use an oil that is solid at room temperature (such as cocoa and coconut oil). Or, you can simply store the emulsion in a cold place, like the fridge, causing the oil to turn solid.

Strategy 2: Surround the droplets with emulsifiers

A disadvantage of thickening an emulsion is that it changes the look and feel of the emulsion. You might not want a thick salad dressing, but a thin, runny one. In that case, adding an emulsifier might be a more suitable choice.

Emulsifiers are components that sits on the interface between water and oil. By sitting there, they prevent the droplets from merging.

Emulsifiers can do this because they have special properties that allows them to sit on this interface. Many emulsifiers are amphiphilic. That is, parts of them prefer to sit in water whereas other parts prefer to sit in fat. It’s why they prefer to sit on the interface, as opposed to in one of the two phases.

amphiphilic emulsifiers in action
An example of an emulsifier in action. This specific emulsifier consists of an round ‘head’ that prefers to sit in water and a tail that prefer to sit in oil.

There are a lot of different types of emulsifiers with each their preferred application. For more tips on using and choosing emulsifiers, read our post on emulsifiers and using them to prevent separation.

Strategy 3: Keep in mind your process conditions

How you make your emulsion can have a major impact on the stability of the emulsion. Two major parameters are especially important to keep in mind: temperature & shear.

Don’t mix too much

To mix water and oil you likely have to mix your mixture quite vigorously. You might use a homogenizer, or a strong mixer. However, you can definitely overmix an emulsion, especially if you’re using emulsifiers to stabilize your emulsion.

Keep in mind that the emulsifier needs to sit on the interface between water and oil to do its job. There should be enough emulsifier to cover the surface of the droplets which are floating in the other liquid.

The total surface area of the droplets depends on the number of droplets present. If there are just a few large droplets that surface area is quite small. However, if there are a lot of tiny droplets, that surface area becomes enormous.

By overmixing, you can create too many tiny droplets. As a result, there no longer is enough emulsifier and the emulsion becomes unstable.

Keep in mind the temperature

It might be easier to mix your water and oil at slightly higher temperatures. At higher temperatures, the viscosity of the liquids goes down. It is easier to mix and pour them than it is at lower temperatures. However, at a higher temperature, it might also be (a lot) easier for the emulsion to separate again. As such, controlling the temperature to your ideal range is crucial.

The video below shows the separation of warm coconut oil from maple syrup. The video has not been sped up, because the mixture is warm, it simply happens quite fast.

No more separation anxiety

Ice cream, custard, salad dressing and many other foods rely on mixing water and oil in an emulsion to create the desired flavor and mouthfeel. However, such systems are notoriously unstable and developing new products with them, or producing them on a factory line can be challenging.

But, by thickening the emulsion, adding emulsifiers and managing your process settings you can make a stable emulsified product.

Think you could do with some help to stabilize and make your delicious emulsions? Don’t hesitate to reach out and request a discovery call so we can discuss your challenges.

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