Here's Why Your Vinaigrette Keeps Separating

Do you often find yourself humming the tune of Al Green's "Let's Stay Together" while you are mixing your vinaigrette? Same. It seems like every time we try to mix up our oil and vinegar to make a simple vinaigrette, they simply won't blend. You've probably unwittingly performed this science experiment yourself when you shook your own oil and vinegar together and thought they had mixed, only to find it was just for a minute. When you buy dressing brands like Kraft or Wish-Bone, they don't seem to have this problem. Why is it happening to your vinaigrette? 

The answer is pretty simple. Per Wonderopolis, the molecules of oil and water are not bonding together. Since vinegar is mostly water, your non-bonded oil will float on top of your vinegar when you combine them. To keep these two ingredients together, you need an emulsifier, a food glue to hold your emulsion together. Per Bon Appetit, egg yolks, mayonnaise, mustard, honey, and tomato paste can all be classified as emulsifiers that you can add to your vinaigrette to help the oil and vinegar stay together. They also can add to the flavor of your salad dressing, making it creamy and sweet. But a member of the Cooking Stack Exchange community says there is more to it. 

Looking for some "seasoned advice," a member of the Cooking Stack Exchange shared that her vinaigrette separated and turned to fellow foodies to diagnose why. One astute member offered that if you are trying to make a vinaigrette sans anything other than oil and vinegar, the oil must be added a little bit at a time while continuously whisking or blending so that the oil can disperse and not all clump together. Another member seconded that how you whisk matters. They suggested that you want to use a zig-zag motion rather than a circular so that the whisk can break up the oil, and it, in turn, can emulsify with the acidic vinegar. That said, the member also cautioned that using an immersion blender or regular blender would produce the most "stable" vinaigrette, and using salt, spices, and herbs will also help with the emulsifying.

However, if your vinaigrette is breaking apart just as you are getting ready to serve guests, you can add a little mayo to quickly bring it back together. Bon Appetit calls this your "silver bullet" and notes that you want to use 1 teaspoon of mayonnaise for every half cup of vinaigrette.