Finally, Homemade Dressing That Won’t Separate or Solidify

A homemade vinaigrette, on the other hand, typically lasts no more than an hour before the oil and the acid start to separate from one another.

Refrigerating it—a must when a dressing contains perishable ingredients such as garlic or shallot—only exacerbates the problem, since extra-virgin olive oil (the classic choice) can solidify at cooler temperatures. You can rewhisk the dressing, of course, but that’s a pain and it never truly comes back together in the same way. 

Fortunately, former senior editor Andrew Janjigian came to the rescue. 

By tweaking the composition of the oil and mimicking the kinds of emulsifiers and stabilizers used in commercial dressings with pantry staples, he was able to create a vinaigrette that not only tastes far superior to the bottled kind, but lasts up to a week in the fridge. The vinaigrette holds together so well, you don’t even need to bother with whisking in the oil— just shake the jar to combine it with the other ingredients.

Here’s how he did it. 

Even a vinaigrette that’s been painstakingly emulsified by slowly whisking oil into the vinegar won’t stay that way for long. But this one holds together for up to a week. It starts with the classic 3:1 ratio of oil to vinegar.

For most of our vinaigrettes, we prefer extra-virgin olive oil or a flavorful nut oil such as walnut or hazelnut. But these oils will eventually start to solidify in the refrigerator because in cold temperatures, their saturated fat molecules lock together and stop moving, forming crystals.

But a polyunsaturated oil, such as vegetable oil, remains liquid at fridge temperature. When combined with olive oil, it keeps the saturated fat molecules further apart so that they can’t readily lock together, slowing crystallization if the mixture is chilled. 

Andrew found that a 2:1 ratio of extra-virgin olive oil to vegetable oil kept the dressing smooth and pourable directly from the refrigerator while still allowing the distinct flavor of the olive oil to come through.

Adding an emulsifying agent is critical. These keep normally incompatible oil and vinegar combined by coating the surface of water droplets, preventing them from merging with one another and helping them remain suspended in oil.

Dijon mustard is a common emulsifier in salad dressings, but for it to be effective, you need to use so much of it that its flavor takes over. That’s why Andrew uses equal amounts of not only mustard but also mayonnaise, which is milder. The egg yolks in mayonnaise contain lecithin, which works the same way as the polysaccharide in mustard to hold oil and vinegar together. 

But the real genius part of Andrew’s formula is adding a stabilizer that almost everyone has in their pantry: molasses. 

He got to this solution in a circuitous way: He noticed that dressing made with thick, syrupy aged balsamic vinegar had remarkable staying power, remaining fully emulsified for several days. Turns out that’s because aged vinegar has an abundance of compounds called melanoidins. Melanoidins are made up of extremely large molecules that increase the viscosity of an emulsion and make it difficult for oil droplets to coalesce and separate from the water.

But Andrew didn’t want to be limited to dressings made with balsamic vinegar. So he searched for other ingredients that contain high concentrations of melanoidins and found molasses. 

Adding just a tablespoon of light molasses was enough to stabilize the dressing; plus, it added an appealing background sweetness. (Don’t use the dark, smoky blackstrap kind, as it tastes too strong and bitter.) 

With all of Andrew’s tweaks, you don’t need to painstakingly emulsify in the traditional way. But you still need to shake the vinaigrette in a jar to help create the emulsion.

Just combine the vinegar, molasses, mustard, and mayonnaise (and salt) together in a jar with a fork and then add the oils in batches, shaking after each addition. The vinaigrette should be glossy and lightly thickened, with no pools of oil on its surface.