How does egg yolk help mayonnaise and salad oils form emulsions?

Egg yolk facilitates the creation of emulsions like mayonnaise by providing lecithins, which act as effective emulsifying agents.1

The process relies on the unique molecular structure of these emulsifiers, which possess both a hydrophobic (water-repelling) portion and a hydrophilic (water-attracting) portion. In a mixture of oil and water:1

• The hydrophobic portion of the lecithin dissolves into the oil phase.1
• The hydrophilic portion dissolves into the aqueous (water-based) phase.1

By bridging these two phases, the egg yolk allows the oil to be dispersed into tiny, stable droplets within the water, preventing the ingredients from separating. This interaction is essential for creating the smooth, uniform consistency characteristic of mayonnaise and various salad dressings.1