How Do Emulsifiers Keep Mayonnaise Intact?
- Anjali Carl
- Dec 1
- 3 min read
It’s a well known fact that oil and water don’t mix. But, mayonnaise stays creamy, chocolate is smooth and glossy, and vinaigrette holds on to salad.
The reason is the unsung hero: emulsifiers.
The incompatibility of water and oil comes down to chemistry. Water is polar and therefore has charged ends that attract each other. Oil is non-polar and doesn’t have this charge differential. When mixed together, like stays with like– so water will bond with water and oil with oil, thereby keeping the two substances separated. This is where emulsifiers step in.
Emulsifiers are molecules with two sides: one end is hydrophilic and likes water while the other end is lipophilic and fat-loving. Molecules with this dual personality are called amphiphilic and is the characteristic that allows emulsifiers to serve as that important bridge.
When emulsifiers are added to a mixture, the molecules arrange themselves at the interface between the oil and water molecules. The emulsifier’s hydrophilic end attaches to the water molecule while the lipophilic end attaches to the oil. This creates little droplets of the mixture, protecting them so they don’t separate again.
What are common emulsifiers used in food?
Lecithin is probably the most common emulsifier, found in soybeans and egg yolks. Eggs are used to make mayonnaise smooth and creamy. And soy lecithin keeps cocoa butter and cocoa solids together to give the smooth texture we love in chocolate. Mustard is another emulsifier and contains mucilage and is used to stabilize vinaigrettes. It’s often why salad dressings call for a spoon of mustard. Proteins can also act as emulsifiers. Milk proteins stabilize ice cream and the proteins in egg whites help stabilize meringues.
Just adding the emulsifier isn’t enough; how it’s added also really matters. When making mayonnaise, as an example, the oil must be added slowly while continuously whisking the egg mixture. The action breaks up the oil into tiny droplets so the lecithin in the eggs can do their magic.
Temperature is also important for emulsifiers. Emulsions tend to be stable when all the ingredients are the same temperature. And that’s why recipes will often call for room temperature eggs or slightly warmed ingredients. The ratio of emulsifier to oil and water also matters. Too much emulsifier can affect the texture and taste. Too little can cause an emulsion to break.
Even well made emulsions can break, and there are different reasons as to why.
Too high of a temperature can cause proteins to denature leading, for example, mayonnaise to separate. Freezing temperatures can affect the balance in cream-based sauces. Acid can alter the charge distribution on emulsifier molecules, affecting their ability to maintain the barrier between phases.
Understanding why emulsions can break helps food scientists find ways to prevent it from happening.
Anjali Carl is a junior at Cedar Park High School in Cedar Park, Texas.They have been excited about food science since making ice cream in a third-grade science class, and now enjoys baking and recipe development. Through their Girl Scout Gold Award project, they created two cookbooks focused on reducing food waste for food pantries and college students. They plan to study food science and eventually become an ice cream chemist.
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