emulsifier

/ɪˈmʌlsəˌfaɪər/
noun
  1. A substance that helps two liquids that do not normally mix, such as oil and water, combine into a smooth mixture.
    • The chef added an emulsifier to the sauce to give it a creamy, uniform texture.
    • Many salad dressings contain an emulsifier like mustard to prevent the oil and vinegar from separating.
    • Lecithin from soybeans is a common emulsifier used in chocolate to keep it smooth.