After five minutes of high-pitched whirring from my immersion blender, my homemade mayonnaise dripped like pancake batter. The Internet promised me a magical moment when my runny eggs and oil would transform into a creamy golden gel.
How much longer will it take?
What am I going to do with this slimy mess?
Did I forget to offer sacrifices to the culinary overlords at Simply Recipes?
Turns out, if you understand how emulsions work, the solution is right under your nose.
What are emulsions?
That’s an emulsion: a stable mixture of 2 liquids that naturally want to separate (the technical term is immiscible).
There are different kinds of emulsions.
- Temporary: This is an unstable emulsion that quickly separates. For example, in a vinaigrette, the oil and vinegar desperately want to form 2 layers.
- Semi-permanent: While this kind of emulsion lasts longer than a vinaigrette, it’s fragile and separates if conditions aren’t perfect, such as beurre blanc and hollandaise sauce.
- Permanent: Mayonnaise is a permanent emulsion because it stays creamy and blended. Milk and cream are permanent emulsions. You can break a permanent emulsion, such as by freezing it, but it takes energy and effort.
Why are emulsions so important?
When my physical therapist taught me how to do a proper deadlift, she warned me, “You’ll start noticing deadlifts in your daily life because we bend over so often to pick something up off the ground.”
Once you learn what emulsions are, you’ll see them everywhere in your kitchen too.
What are examples of culinary emulsions?
- Homogenized milk: Milk and cream are globules of fat suspended in water (“oil-in-water” emulsion)
- Butter: Margarine and butter contain water droplets suspended in fat (“water-in-oil” emulsion)
- Salad dressings and vinaigrettes: Oil and water are mixed with herbs and aromatics
- Sauces: Beurre blanc, gravy, hollandaise, lemon butter, mayonnaise, rémoulade, tartar sauce
- Chocolate and hot chocolate: This beloved candy is cocoa butter (and milk in the case of milk chocolate) and water mixed together.
- Espresso: The foam in espresso is coffee oil suspended in water giving it a creamy texture without milk.
NOTE: Emulsions aren’t only in food. You find them in your skincare (moisturizers are emulsions), hair products, medicines, and more.
Understanding how emulsions work helps you create drool-worthy vinaigrettes, fancy French sauces, and magnificent mayonnaise so thick you could use it as a face mask.
When you know the basics of emulsions, you’ll understand the why behind the instructions in a recipe and feel confident in applying the technique.
Even if a recipe fails, you’ll understand how to fix it and be likelier to succeed next time.
Nerdy secrets of how emulsions work
In the mid-1840s, Théodore Nicolas Gobley, a French pharmacist and biochemist, suspected egg yolks and the human brain shared something in common. But he couldn’t prove it, yet. Worse, his ideas disagreed with the leading experts of the day.
Gobley came from a wine-trading family in Burgundy where he grew up around relatives who distilled spirits. Plenty of childhood tinkering laid the groundwork for his research. It took over 30 years, including inventing a new instrument, for him to discover brains, fish roe, and egg yolks contain an unknown yellow-brownish fatty substance.
This fatty substance is a critical ingredient to keep your homemade sauce homogeneous. But first, what is it and why do we need it?
Like newborns and sleep, oil and water don’t get along. You need a lot of effort and energy to coax them into a harmonious state.
Fill a glass of water to the brim. Watch the water bulge over the top of the glass without spilling.
Surface tension is the force that pulls water to itself and stops it from spilling over. It also draws oil to itself.
Have you noticed how it doesn’t matter how hard you shake vinaigrette, it separates into oil and vinegar?
Drops of oil love joining other oil drops to form a bigger droplet of oil. That’s why emulsions separate over time because oil finds oil, and water attracts water.
The key to mixing oil and water is to reduce the surface tension where the two meet (called the interface).
We reduce surface tension when we use a lot of energy to break one of the liquids apart into small droplets and spread it throughout the other liquid.
- Oil-in-water emulsions: Oil breaks into droplets and spreads throughout water (vinaigrette and milk are examples)
- Water-in-oil: Water droplets disperse in oil (butter and margarine are examples)
There’s another way we can reduce surface tension. It’s a more powerful way to keep your velvety sauce intact.
Apply emulsion basics to cooking: What you need to know
Wouldn’t it be cool if we could find glue that sticks to both oil and water? If either tried to escape, this glue would hold it back so that the droplet would stay trapped in the mixture.
This glue exists: it’s an emulsifier.
What is an emulsifier?
Picture a hairpin with a round head. That’s how emulsifiers look (simplified, of course).
- The round head is electrically charged: Water attracts the head whereas oil repels it (“hydrophilic“)
- The long tail is electrically neutral: The tail attracts oil and repels water (“hydrophobic” or “lipophilic“)
I love the analogy of a pincushion Processing Magazine uses to describe how emulsifiers work.
Imagine an oil droplet. The emulsifier’s long tail points towards the oil droplet while the emulsifier’s head attracts water. It looks like a pincushion where emulsifier molecules surround an oil droplet.
NOTE: For the geeks, check out the math behind emulsifiers.
Emulsifiers work in 2 ways to keep your mixture stable:
- Emulsifiers act like a fence surrounding an oil droplet so it can’t meet up with another oil droplet.
- Because emulsifiers hang out at the interface between an oil droplet and the surrounding water, there is less surface tension.
TAKEAWAY: To create a stable emulsion, you must have enough emulsifier to “surround” the oil droplet. If your mayonnaise isn’t thickening into a creamy sauce, add more emulsifier.
The most powerful culinary emulsifiers
Powerful emulsifiers are sitting on your pantry and fridge shelves. You glance at them every day without realizing the magic they hold.
In 1874, after 3 decades of analyzing lipids and publishing his incremental findings built on his and others’ work, Théodore Gobley revealed the yellowish-brown fatty substance. He isolated it and called it lecithin, named after the Greek word for egg yolks, lekithos.
Lecithin is one of the most powerful culinary emulsifiers.
You’ve seen lecithin on the label of store-bought foods, such as chocolate, ice cream, and goopy powdered gravy mixes that smell like instant ramen.
Lecithin naturally occurs in egg yolks, seafood, soybeans, sunflower oil, and many more ingredients.
Mayonnaise benefits from egg yolks to keep it thick and creamy. That’s why many salad dressing recipes include an egg yolk to stick the oil and vinegar together.
Mustard contains a weaker emulsifier around its husk called mucilage, a thick, gluey substance (sounds like mucus). Other plants have mucilage, such as flaxseed and chia seeds. Picture how chia seeds contain a slippery, transparent, gummy gel when you hydrate them. That’s mucilage.
It’s no accident mustard is included in most mayonnaise and vinaigrette recipes.
Milk contains lecithin and casein. Both are emulsifiers to keep the fat and water in dairy evenly mixed.
TIP: Milk with a cream top isn’t emulsified whereas homogenized milk is. You can freeze and thaw homogenized milk without it separating.
When we froze heavy whipping cream—which isn’t homogenized, the fat and water separated after defrosting. There’s no way for us to mix them back together.
NOTE: If you’re vegan, you might recognize plant-based emulsifiers and stabilizers, such as xanthan gum and gum Arabic. These keep your emulsions stable when you can’t use ingredients like egg yolks and butter.
Common emulsion mistakes
“French food is fancy and hard to cook,” my friends tell me. “I’m not a Michelin star restaurant chef.”
French cuisine—cooking in general—seems difficult because you need to learn the techniques first. Same with emulsions.
It’s always intimidating the first time you shake up salad dressing, churn cream into butter, and concoct gluten-free, keto-friendly vegan snacks that aren’t cardboard (triple threat!). After all, why can’t you buy these things at the store?
You can. I do.
But it’s worth making sauces—especially mayonnaise at home—to understand how they work and reap the joy of making things from scratch. Plus, if you’re out of mayo, it sure would be nice to know how to make some.
Learning new techniques is easier when you know common mistakes and how to overcome them.
1. Not following the recipe
Who else is cheeky in the kitchen?
Last week, I practiced making mayonnaise to prepare for this article. After glancing at 3-4 recipes, I thought, “I’ve made mayo before. How hard could it be?”
The thing about making mayonnaise—and most emulsions—is it’s more like baking than cooking.
Creating emulsions requires precision. Anytime you deviate from a well-tested recipe, you better know what you’re doing.
The most common reason your emulsion doesn’t work is not having enough emulsifier for the amount of oil you’re using (in an oil-in-water emulsion). The oil droplets want to form big droplets rather than spread throughout the water.
Unless you’re the nerd with a microscope, you can’t see how much emulsifier you need with the naked eye. The next best thing is weighing your eggs because a medium egg yolk contains less lecithin than an extra-large egg yolk.
Takeaway: Follow the recipe. Only eyeball if you’ve made the sauce or dressing over 10 times. Or you’re OK with failure (see #5 below).
2. Adding oil too fast
What do you think happens if you dump all the oil in at once?
The oil merges together to create a layer on top of the water (or vinegar). When you mix, the sauce stays thin because the oil has stuck together into big droplets.
That’s why most recipes instruct you to add the oil drop by drop.
Even the most aggressive recipes, like Serious Eats’s mayonnaise, which tells you to pour all the oil in, assume your blender slowly pulls the oil into the egg yolk and vinegar mixture.
I add butter pat by pat or oil in a trickling stream until I feel confident my emulsion has stabilized. Then I add it in faster once I’ve mastered the recipe.
What if you break the sauce?
TIP: The quick-and-dirty answer to fixing a broken emulsion is adding more emulsifier. That’s why the most common advice for how to fix a broken mayonnaise is to add another egg yolk, which means more lecithin. If you’re making a butter sauce, the butter is the emulsifier. So cool down your sauce and add in more squares of butter to save it.
Takeaway: Control and patience are your friends. I like to pause to check if the oil is mixed in before I add more.
3. Overheating the sauce
What happens to eggs and butter in a hot pan?
Your butter melts. Eggs fry.
The aroma of brown butter and Saturday brunch are the opposite of what you want when making delicate sauces like beurre blanc and hollandaise.
Because emulsions are delicate, temperature matters. Too hot and too cold risk breaking your emulsion.
For example, beurre blanc requires stirring in pats of cold butter. They soften and give you a creamy, whipped sauce. If you melt the butter, you get a runny, yellowy oily sauce.
Hollandaise separates when you overheat it because you cook the egg yolks, thereby breaking the emulsion.
NOTE: Overheating a sauce is like breaking an egg. Can’t undo it. Prevention is key.
Takeaway: Use a thermometer when you’re cooking a sauce that’s heat sensitive. If you don’t have one, go slow on low or medium-low heat. Your sauce should get thicker. If it’s getting runnier, turn down the heat and remove the pan to let it cool down.
4. Helpful equipment: Make emulsions easier
You can disperse oil droplets into water (or water droplets for water-in-oil emulsions) by hand or using powerful kitchen appliances.
Here’s the most useful equipment when whipping up an emulsion:
- For salad dressing: Wide-mouth mason jars with airtight lids will be critical for shaking the oil into the vinegar. A bottle with a mini whisk also works. They’re designed for pancake mix or protein shakes, which make them great for mixing oil into vinegar (disclosure: I once received a free one at a conference).
- For power tool lovers: Most of us are going to use a kitchen appliance, such as a blender or food processor to break up the oil into droplets. I love using my immersion blender and my mini food processor.
- For hand mixing: Do you live in the middle ages? At least an ergonomic whisk and mixing bowl speed up the process.
Takeaway: There’s no award for doing it by hand except for getting a wrist workout.
5. Not giving it a few tries
The first time I baked kale chips, I sprinkled too much salt. The chips tasted like I was munching on a salt shaker. By the 4th attempt, they were crispy and perfectly seasoned.
The worst mistake when learning to make a sauce or dressing is giving up if you fail the first time because the emulsion breaks. Scratch that, the worst mistake is quitting without trying.
Takeaway: Just like how a baby doesn’t learn to walk the first time he takes a step, assume you need to try the recipe at least 3 times to nail a new technique.
TIP: If it’s still not working by the third time, comment on the recipe or email the writer to ask for help.
As a final tip, you’re smart to have a store-bought version as a backup for special occasions, such as cooking for anniversary dates, in-law dinners, and the folks from the regulatory office you’re definitely not trying to bribe to get your medical device certified.
With plentiful practice, it won’t take you close to as long to become a skilled sauce maker as it took Théodore Gobley to isolate lecithin.