What ingredient is typically used to emulsify a vinaigrette?

Mustard is commonly used as an emulsifier in vinaigrettes due to its unique properties that help stabilize the mixture of oil and vinegar. When mustard is blended into the vinaigrette, its molecules form a bridge between the oil and vinegar, creating a stable mixture rather than allowing the two to separate. This emulsification not only helps achieve a smooth and cohesive texture but also enhances the flavor profile of the vinaigrette.

The other ingredients listed do not have the same emulsifying effect as mustard. Vinegar alone does not help stabilize the mixture; it serves as the acidic component. Water can be used in some recipes but does not contribute to emulsification effectively. Salt enhances flavor but does not assist in creating an emulsion either. Thus, mustard is the preferred choice for achieving a balanced, flavorful vinaigrette.