If you’ve eaten homemade mayonnaise, you know that its custardy richness and delicate tang are clean and clear in a way the commercial stuff just isn’t. It lights up anything it touches—from egg or potato salad to lobster rolls to boiled artichokes to green goddess dressing—and is the only condiment worth slathering onto a BLT or high-summer tomato sandwich. It’s the preparation President Calvin Coolidge waxed nostalgic about (his Aunt Mary’s, specifically) to the Spokesman-Review and one that fascinated—and often stymied—Julia Child. British food writer Elizabeth David urged her readers to make “plenty of it” when hosting guests, since “this beautiful golden ointment‑like sauce is really the pivot and raison d’être of the whole affair.”
There are practical perks, too: Making a batch takes minutes, most of the work can be done in a food processor, and there’s a good chance you have all the ingredients (eggs, oil, lemon juice or vinegar, Dijon mustard, salt, and sugar) on hand. But if you haven’t made mayonnaise, I’m guessing it’s for one of two reasons. First, homemade mayonnaise is prone to “breaking,” meaning that the oil and water fail to emulsify and remain a runny, greasy mess instead of forming a thick, creamy spread. Second, unlike commercial mayonnaise that’s made with pasteurized eggs (pasteurization kills any potential pathogens in the eggs), homemade versions are typically prepared with unpasteurized raw eggs, which limit their food safety.
But what if there was a truly reliable recipe for homemade mayonnaise with a longer storage time? For the sake of BLTs everywhere, I had to try.
To understand how mayonnaise works (or why it doesn’t), you first have to understand emulsions—combinations of two liquids that don’t ordinarily mix, such as oil and water. The only way to combine them is to whisk or process them so vigorously that one of the two ingredients breaks into tiny droplets that are suspended in, and separated by, the other. In mayonnaise, it’s the oil that gets broken up. (According to food science writer Harold McGee, 1 tablespoon of oil in mayonnaise can break into about 30 billion separate droplets.) Eventually, the droplets are small enough that they remain separated by the water and the two fluids effectively become one. A third ingredient, called an emulsifier, helps stabilize the mixture (for more information, see “Mayo Under the Microscope”).
Without an emulsifier in the mix, many of the tiny oil droplets start to find each other and coalesce, eventually “breaking” the mixture back into two separate fluids. And that’s where the egg yolks come in: They contain a powerful emulsifier called lecithin that stabilizes the emulsion by surrounding the oil droplets, preventing them from finding one another and merging into greasy pools.
But there’s more to making a successful mayonnaise than simply adding an emulsifier. After whipping up several batches, I realized that using a precise mixing method and a sufficient amount of water is just as critical.
Most mayonnaise recipes that are made in the food processor call for placing all the ingredients except the oil in the processor bowl and then very slowly drizzling in the oil while the machine is running. It’s essential that the oil—especially the first few tablespoons—be added gradually, because doing so establishes a “base emulsion” with plenty of oil droplets that are well coated with lecithin. Once formed, this base helps emulsify the remaining oil.
Here’s where many food processor recipes get into trouble: As soon as the motor starts running, the yolks and the lemon juice or vinegar get sprayed up the sides of the bowl, so when you first add the oil, there is not enough liquid volume in the bowl to engage the processor blade, and the oil merely collects below the blade in a greasy pool. As you keep drizzling in the oil, there will eventually be enough liquid to engage the blade, but since so much of the water from the yolks and acid is lost to the sides of the processor bowl, there won’t be enough of it left to keep the oil droplets separated. And when the oil droplets aren’t separated, the emulsion fails.
Given that, I wanted to find a more reliable way to create a base emulsion, so instead of mixing the mayonnaise entirely in the food processor, I started the emulsification by hand. After whisking together the rest of the ingredients in a bowl, I whisked in the first ¼ cup of oil until it was incorporated. A few oil droplets floated to the surface, but enough of it was emulsified that I could move the rest of the mixing to the food processor.
From there, I proceeded as most recipes do, drizzling in the remaining 1¼ cups of oil in a deliberately slow, steady stream. (Adding the oil too quickly is one of the most common causes of broken mayonnaise.) To be sure that I’d captured all the yolk mixture, I scraped down the sides of the bowl and processed for another few seconds. The result was lush and glossy but likely still fairly perishable.
Time to take care of any potential pathogens with DIY pasteurization. To pasteurize liquid eggs, all you have to do is heat them to 160 degrees. It was fast and easy to whisk a couple of yolks until smooth and pop them into the microwave before I started the hand‑mixing step, and I made sure to stop and stir them regularly so that they heated evenly. But I soon realized that I couldn’t heat the yolks alone; at that temperature, their proteins unraveled and tangled with each other tightly enough to trap water and turn the yolks semisolid. And without that free water, there wasn’t enough left to hold the oil droplets (never mind that their semisolid state would make them impossible to blend).
To keep the yolks fluid, I heated them with two added ingredients: 3 tablespoons of water, which was enough to help keep the proteins separate from one another but not so much that it noticeably diminished the mayo’s flavor or creaminess, and the 4 teaspoons of lemon juice I was already using in the mayonnaise, which contributed more water.
From there, I wasted no time whisking in that initial ¼ cup of oil to help the yolk mixture cool down (further prevention against those yolk proteins thickening the mixture). I also made a point of adding the mustard at this stage, since it, too, is an emulsifier—albeit a weaker one than egg yolk—that contains water and would support the base emulsion.
A few minutes later, I had gorgeously dense, satiny mayonnaise that I could transfer to an airtight container for weeks of safekeeping in the refrigerator.