Emulsion That Holds for Several Days
No Special Ingredients Necessary
Template Adaptable to Multiple Flavor Variations
I make a lot of salads, so I like to mix up a large batch of vinaigrette to last for several days. But no matter how carefully I whisk the oil into the other ingredients, it doesn’t stay emulsified for long. Even our Foolproof Vinaigrette only holds together for a few hours—fine for dinner one night but not the next. One option is to rewhisk the dressing in a bowl, but it never truly comes back together.
But recently I stumbled on a potential solution in an unusual ingredient. Finding myself short on wine and sherry vinegars, I supplemented with some of the thick, syrupy aged balsamic vinegar that I would ordinarily drizzle on steak, good cheese, or berries. This vinaigrette had a thick, viscous consistency. Not only that—and this was key—but it had remarkable staying power. The mixture remained fully emulsified the next day and for several days after that. It wasn’t until the week was nearly over that a thin layer of vinegar sat at the bottom of the jar—and even then, a quick shake was all it took to restore a tight emulsion. This was a dressing I wanted to investigate further.
The Three Ms
I wanted to create a basic recipe for long-lasting vinaigrette, a template in which I could switch up the acid, using any type of wine vinegar or even lemon juice. That meant I had to figure out what property of the aged balsamic gave the vinegar its remarkable hold on the emulsion. Once I had discovered that, I’d see if I could replicate the effect with other ingredients.
I thought the balsamic’s high concentration of sugar might be the answer, since it’s known to lend viscosity to dressings. I prepared two batches of Foolproof Vinaigrette, combining (for now) white wine vinegar, Dijon mustard (valuable for its tangy flavor and emulsifying properties), a touch of mayonnaise (another emulsifier), salt, and pepper, plus a few teaspoons of honey and maple syrup; then I whisked 3 tablespoons of extra-virgin olive oil into each. Both sweeteners thickened up the dressing, but neither one produced a dressing that held for more than an hour or so.
It wasn’t until I asked our science editor that we hit upon the key component: melanoidins. These compounds, abundant in aged balsamic vinegar, are formed when sugars and proteins are heated and undergo the Maillard reaction, the chemical reaction that generates deep browning and flavor. Because the molecules of these compounds are extremely large, they increase the viscosity of emulsions so much that it becomes difficult for the oil droplets to move around and coalesce into larger droplets and eventually separate from the water; thus, the dressing is very slow to separate. (Melanoidins also happen to be responsible for the aged vinegar’s inky color.)
Knowing that, I did a search for other ingredients that contain similar concentrations of melanoidins, and sure enough, I found one sitting in my pantry: molasses. The trick would be to add enough of the gooey sugar syrup to stabilize the dressing but not so much that its flavor was pronounced, so I made more batches of the vinaigrette until I hit upon the ideal combination: ¾ cup of extra-virgin olive oil, ¼ cup of vinegar (our standard ratio of oil to vinegar for a balanced vinaigrette), 1 tablespoon each of mustard and mayonnaise, and 1 tablespoon of light molasses (the dark, smoky blackstrap variety would taste too strong and bitter). The emulsion held for a week, and the dressing tasted even better than with the balsamic because the molasses’s flavor wasn’t as recognizable and left only a bit of background sweetness.
There were just two more questions to answer: If the melanoidins created such a strong emulsion, did I need the emulsifying powers of the mustard and mayonnaise? And was it necessary to slowly whisk in the olive oil, or could I simply shake the jar to mix the components?
Science: Secrets to a Dressing with Staying Power
Our Make-Ahead Vinaigrette relies on mustard and mayonnaise (emulsifiers) to help the oil and vinegar combine into a unified sauce. Mustard contains a polysaccharide, and the egg yolks in mayonnaise contain lecithin; both of these agents attract oil and are compatible with water, so they hold the two disparate components together. Molasses (a stabilizer) contains large compounds called melanoidins that increase the viscosity of the emulsion and make it difficult for the oil droplets to coalesce and separate from the water.
I made three more batches of dressing, omitting the mustard in one, the mayo in a second, and both in a third. In each case the dressings lacked cohesion—particularly the mustard-free batch. The emulsion completely separated after just a few hours. Eventually, I learned that mustard and melanoidins work differently. While the mustard helps the emulsion form, the melanoidins prevent it from separating. It’s basically the difference between emulsifiers and stabilizers.
As for shaking the dressing as a method of forming the emulsion, it worked beautifully as long as I stirred together the vinegar, mustard, mayonnaise, molasses, and salt with a fork and then added the oil ¼ cup at a time and shook vigorously. Over the coming days, a very thin layer of vinegar did eventually settle out onto the bottom of the jar, but it was easily reincorporated with a quick shake before serving.
Our Make-Ahead Vinaigrette stays emulsified for up to a week—much longer than a traditional vinaigrette or plain oil and vinegar.
Two Oils Are Better Than One
The only hitch to including the mayonnaise was that the dressing needed to be refrigerated, and doing so caused the oil to solidify and the emulsion to break completely once it came to room temperature. But I had an idea.
I knew that extra-virgin olive oil solidifies when its molecules form a lattice and crystallize, and I knew I could prevent crystallization by cutting it with another type of oil. Vegetable oil would be the easiest and most neutral addition, so I tried ratios ranging from 10:1 to 2:1 of olive oil to vegetable oil and eventually found that the 2:1 ratio kept the dressing smooth and pourable directly from the refrigerator while still allowing the distinct flavor of the olive oil to come through.
My recipe was not only ideal for making ahead, but without the whisking, it was easier than any other vinaigrette I’d ever made. Plus, I could substitute other oils (like hazelnut or walnut) for the olive oil, use any number of wine vinegars or lemon juice, or even throw in aromatics like garlic and shallots. The template complemented just about any salad green I tried, from plain leafy lettuces to the heartier combinations I created using cooked chicken with spinach, watercress, and arugula. Making vinaigrette had just become a weekly rather than a daily affair.