Mayonnaise is a stable emulsion built from egg yolks, vegetable oil, an acid like vinegar or lemon juice, and salt, with Dijon mustard often added to keep the mixture from breaking. At its core, the condiment is roughly 70 to 80 percent oil by weight, with tiny droplets suspended throughout a water-based phase thanks to emulsifiers in the yolk. Commercial jars on American shelves also contain pasteurized eggs, stabilizers like xanthan gum, and occasionally a touch of sugar, which together give the spread its familiar creamy texture and weeks-long shelf life.
The sections below walk through the core ingredients that define mayonnaise, the science that holds them together, and the variations available on the shelf and in your kitchen.
The Core Ingredients That Define Mayonnaise
Look at any back-of-jar ingredient list and the same handful of players repeat across brands, whether you hold a Hellmann’s squeeze bottle or a glass jar of Duke’s. Strip away the marketing language and four or five workhorse items account for nearly everything in the jar.
The Must-Have Five
- Egg yolks: The foundational emulsifier, supplying lecithin to bridge oil and water into a stable mixture.
- Vegetable oil: Forms the bulk of every jar, and FDA standards require at least 65 percent by weight in products labeled as mayonnaise.
- Vinegar or lemon juice: Provides acidity that sharpens flavor and helps stabilize the emulsion by lowering pH.
- Salt: Seasons the base and subtly enhances the perception of richness without tasting overtly salty.
- Dijon mustard: A common addition that stabilizes the emulsion and adds a tangy backbone to the flavor.
Egg yolk does the heavy lifting because lecithin, a phospholipid concentrated in the yolk, has one end that loves water and another that loves fat. Whisking oil into yolk lets each lecithin molecule wrap a droplet and keep it from merging with its neighbors. That microscopic wrapping is what turns two things that normally refuse to mix into the silky, opaque spread on your sandwich.
The Hidden Helpers
Commercial versions stretch that base with a few extras that rarely appear in homemade recipes. Pasteurized eggs remove the salmonella risk tied to raw yolks, while xanthan gum and similar gums act as secondary stabilizers that protect the emulsion during shipping and temperature swings. A whisper of sugar softens acidity, and preservatives such as calcium disodium EDTA extend shelf life by slowing oxidation. None of these are strictly necessary to make mayonnaise, but they let a jar survive six months on a warehouse pallet and still look smooth when it reaches your fridge.
Why These Ingredients Work: The Science of the Emulsion
The reason a jar of mayo doesn’t separate into a greasy puddle on top and a watery layer on the bottom comes down to physics at a scale you can’t see. Each teaspoon holds billions of microscopic oil droplets, and an emulsifier keeps them locked in place like balloons floating in a thin pool.
An Oil-in-Water Emulsion
Tiny oil droplets suspended in a water-based continuous phase define the scientific structure of mayonnaise as an oil-in-water emulsion. The opposite, a water-in-oil emulsion, describes butter and margarine, where water droplets sit inside a fat matrix. Knowing which type you’re making matters because the two behave differently in dressings, dips, and binders. Oil-in-water emulsions feel lighter on the tongue and pour more readily, which is why mayo slides off a spoon while melted butter clumps.
Why Lecithin Does the Bridging
Lecithin molecules carry a hydrophilic head that bonds with water and a hydrophobic tail that bonds with oil. When oil hits a yolk-and-vinegar base under whisking, each lecithin molecule quickly positions itself at the boundary of a forming droplet. The result is a charged, protective coating that keeps neighboring droplets from coalescing. Slow addition gives the lecithin time to coat each new droplet before it can merge with another, which is why pouring oil in a thin stream produces a thicker, more stable mayo than dumping it all at once.
The Role of Acid and Mustard
Acid from vinegar or lemon juice does more than brighten flavor. Dropping the pH thickens the proteins in the yolk and firms up the emulsion, which is why a finished jar sits up on a spoon rather than running off. Mustard contains additional emulsifying compounds, including proteins and a small amount of mucilage, that act as a backup stabilizer when the oil-to-yolk ratio drifts too high. Many classic recipes lean on mustard precisely because it widens the window of conditions under which the emulsion holds together.
Pour the oil as slowly as you can manage for the first third of the recipe, then accelerate once the base thickens. Patience up front is the difference between glossy mayo and a broken, oily puddle.
Raw Eggs, Pasteurization, and Food Safety
The egg question is the one that stops most home cooks cold. Commercial mayonnaise is safe because the eggs have been pasteurized, but a homemade batch built on raw yolks carries a small, real risk that deserves a clear-eyed look.
Why Commercial Mayo Is Safe
Industrial manufacturers heat eggs to a temperature high enough to kill salmonella before they ever enter the mixing tank. The finished product is also acidic, with a pH that usually sits between 3.6 and 4.0, well below the 4.1 threshold at which common foodborne pathogens struggle to grow. Combined with refrigeration and the protective effect of the oil layer, this is why a sealed jar can sit on a grocery shelf for months without becoming a hazard.
The Homemade Risk
Raw-egg homemade versions carry a small but documented salmonella risk that hits pregnant people, young children, the elderly, and anyone with a compromised immune system hardest. The U.S. Department of Agriculture estimates that roughly 1 in every 20,000 eggs may be contaminated with salmonella, and that figure is enough to take seriously even if the odds on any given yolk are low.
Practical Ways to Lower the Risk
Pasteurized shell eggs sold in cartons offer a safer middle ground for homemade versions, because the pasteurization happens inside the shell without cooking the egg. A quick at-home pasteurization, heating yolks and acid to 160°F while whisking constantly, also works if you have a reliable thermometer. Refrigeration and prompt use within a few days remain essential for any batch made without commercial pasteurization, since pathogens grow fastest at room temperature.
Food safety narrows the practical gap between pantry-stable commercial jars and what you can safely whip up at home.
Store-Bought Versus Homemade: What Actually Changes
Both options taste great on a sandwich, but the ingredient lists, textures, and nutritional footprints diverge in ways that matter depending on what you want from your mayo.
| Feature | Store-Bought Mayo | Homemade Mayo |
|---|---|---|
| Eggs | Pasteurized, standardized | Usually raw, fresh from the shell |
| Oil | Soybean, canola, or blend, neutral | Any oil you choose, including olive or avocado |
| Acid | Distilled vinegar, often with lemon juice | Fresh lemon juice or any vinegar on hand |
| Stabilizers | Xanthan gum, sometimes guar gum | None, relies on yolks and mustard |
| Preservatives | Calcium disodium EDTA common | None |
| Shelf life | Several months unopened | One to two weeks refrigerated |
| Calories per 100 g | Around 700 to 800 | Similar, driven almost entirely by oil |
Commercial brands such as Hellmann’s, Best Foods, and Duke’s rely on pasteurized eggs, standardized oil blends, and added stabilizers for predictable texture across millions of jars. Homemade versions offer fresher flavor and full control over oil type, with no preservatives and no added sugars. Soybean oil dominates American brands because of its neutral taste and low cost, while canola, sunflower, and olive oil appear in premium and European versions.
Reading labels reveals hidden ingredients such as sugar, calcium disodium EDTA, and natural flavors that shift the flavor profile in subtle ways. Caloric density sits around 700 to 800 calories per 100 grams regardless of brand, driven almost entirely by oil content. The difference between a $4 jar and a homemade batch rarely shows up on a calorie count, but it does show up in how clean the ingredient panel reads.
Oil Choices and How They Shape Flavor and Texture
The single biggest decision you make when building mayo is which oil goes in the jar. Oil accounts for roughly three-quarters of the volume, so its flavor profile dominates everything you taste.
Neutral Oils
Commercial American brands lean on soybean and canola oils because their neutral flavor lets vinegar tang shine through without competition. Soybean oil in particular has been the workhorse of the U.S. industry for decades because it is cheap, mild, and stable on shelves. Canola oil behaves similarly and brings a slightly different fatty acid profile, with more monounsaturated fats and less saturated fat than soybean.
Flavor-Forward Oils
Olive oil lends a fruity, peppery note that defines Spanish and Mediterranean styles, though extra-virgin olive oil can turn bitter at high proportions because of its polyphenol content. Avocado oil brings a buttery richness and a higher smoke point, appealing to health-conscious cooks and to anyone baking with mayo at higher temperatures. Sunflower oil offers a mild taste similar to soybean but with a different fatty acid profile and a slightly thinner finished texture.
Blending for Balance
Blending two oils lets you combine flavor neutrality with nutritional or sensory goals. A 50/50 mix of light olive oil and canola oil, for example, delivers olive flavor at half the intensity while keeping the texture light. This trick lets you taste the oil without letting it overpower the acid, mustard, and salt in the rest of the recipe.
Vegan, Allergy-Friendly, and Regional Variations
The classic formula depends on eggs, which makes traditional mayo off-limits for vegans, people with egg allergies, and anyone avoiding animal products for religious reasons. Plant-based kitchens have developed workarounds, and several international styles offer alternatives without needing any swaps at all.
Vegan Mayo
- Aquafaba: The liquid from canned chickpeas mimics egg white proteins and emulsifies oil effectively, producing a finished texture close to traditional mayo.
- Soy protein: Serves as the emulsifying base in many commercial plant-based brands, including Just Mayo and Hellmann’s Vegan.
- Pea protein: A newer option that performs similarly and avoids common soy allergens.
Vegan mayo performs nearly identically in dressings, dips, and binders, though it can be slightly thinner than egg-based versions and may require extra acid or a touch more mustard to firm up. The science is the same: an oil-in-water emulsion held by proteins rather than yolk phospholipids. The result is close enough that most recipes don’t need adjustment.
Regional Styles
| Style | Distinctive Ingredients | Flavor Profile |
|---|---|---|
| Kewpie (Japan) | Yolks only, rice vinegar, MSG | Deeper umami, richer mouthfeel |
| Thomy (Germany) | Sunflower oil, mustard, sugar | Slightly sweet, mild tang |
| Spanish mayonnaise | Olive or sunflower oil, garlic | Robust, often garlicky |
| British salad cream | Cooked custard base, vinegar, mustard | Sweeter, looser, tangier |
Japanese Kewpie stands apart for using only egg yolks with no whites, rice vinegar, and MSG for deeper umami flavor. German Thomy and Spanish mayos often lean on sunflower or olive oil and a sharper mustard note, while British salad cream is a looser, sweeter cousin rather than a true mayonnaise. Each variation answers the same question with slightly different ingredients, which is why a single condiment can taste so different depending on where the jar was made.
Bottom Line
Mayonnaise is fundamentally oil, water, and an emulsifier held together by chemistry that has worked in kitchens for centuries. The ingredients are simple, the science is precise, and the variations exist mostly because people kept tinkering with the oil, the acid, and the emulsifier until something new and worth eating emerged. Read the label, choose the oil that fits your flavor, and you’ll never wonder what is in the jar again.
FAQ
Is mayonnaise made with raw eggs?
Pasteurized eggs in commercial jars eliminate salmonella, which is why store-bought mayonnaise is widely considered safe to eat. Homemade versions often use raw eggs, so choose pasteurized shell eggs or heat the yolks and acid to 160°F if you’re cooking for anyone in a high-risk group.
What oil is used to make mayonnaise?
Most American brands use soybean oil because it’s neutral and inexpensive, while canola, sunflower, and olive oil appear in premium and international versions. The FDA requires at least 65 percent vegetable oil by weight in anything labeled as mayonnaise.
Is mayonnaise dairy free?
Oil, egg yolks, vinegar or lemon juice, and salt make up the traditional formula, so the product contains no milk or cream at all. Always check the label for added milk derivatives if you have a severe allergy, since some specialty brands add cultured dairy for tang.
Why doesn’t mayonnaise contain milk?
Emulsified oil droplets deliver the creamy mouthfeel, which is why traditional formulations skip milk fat entirely and remain dairy-based-free. The result is a spread that’s higher in fat than butter but completely free of lactose and casein.
What’s the difference between mayo and Miracle Whip?
Miracle Whip is technically a salad dressing rather than mayonnaise, and it contains added sugar, a cooked starch base, and more vinegar for a sweeter, tangier, lighter flavor. Regular mayo stays closer to the egg-and-oil formula with a richer mouthfeel.
Is mayonnaise vegan?
Egg yolks in the standard recipe disqualify mayonnaise from a vegan diet, since animal products are part of the core formula. Vegan versions replace the yolks with aquafaba, soy protein, or pea protein to create the same emulsion, and several major manufacturers now offer plant-based jars in regular grocery aisles.
