How to Choose the Right Mustard for Vinaigrette
Any good vinaigrette contains oil and water based ingredients that, if we remember our basic chemistry, don’t really like each other. To help these diametrically opposed partners get along and work as one, you need an emulsifier.
An emulsifier, in its simplest form, is an ingredient that helps oil and water remain unseparated. Mustard – besides adding flavor – is also an excellent emulsifier, thanks to the mucus, the outer coating of the mustard seeds. But not all cooked mustards have the same amount of mucus, which means that not all cooked mustards are suitable for vinaigrette.
Typically, bright classic yellow mustard has no mucus. When Cook’s Illustrated compared dry, yellow, Dijon mustard and coarse mustard in a vinaigrette recipe, they found that the dressing made with dijon and coarse, the most sticky dressing, stabilized the dressing better than the other two. … (A sample from Dijon was held together for several hours, while in the stony ground everything remained emulsified for a full week.) So, while mucus is terrible to talk about (and inject over and over again), its emulsifying ability cannot be denied.
Not sure how this translates at the grocery store? Look for whole grain options. (Dijon is a finely ground whole grain product.) Your dressing will pair well, stay in the emulsion longer, and taste (in my opinion) much better than anything with plain yellow.