What is the role of egg yolk in mayonniase? What happens to the emulsion when the egg yolk was reduced by 50% or omitted? Explain why? Egg yolk is the emulsifying agent. Without it mayonnaise is basically a vinaigrette. If you omit egg yolk entirely your mayonnaise will not emulsify (thicken), if you reduce it by half, it will still work, but may not be as stable, or as easy to make. There an intriguing question bugging me. Why can't we use use egg yolk instead of GMS( glyceryl monostearate) in margarine. I mean GMS is artificial emulsifier so it much be the same as egg yolk ? or egg yolk cannot , too oily ??