Question

Otis watches a cooking show on making mayonnaise. The chef dissolves salt and sugar in vinegar. She mixes in an egg yolk, and then mixes in oil until the ingredients are completely blended together. The chef says that it’s great on sandwiches and that it can be stored without separating.

Which best describes the purpose of the egg yolk in the recipe?

It allows the oil to change from liquid to a gas in order to form bubbles.
It acts to hold the vinegar and oil together in a colloid.
It helps the vinegar be able to form a solution with the salt and sugar.
It mixes with both the vinegar and oil to form a suspension.

Answer 1

It acts to hold the vinegar and oil together in a colloid.

The egg yolk contains emulsifiers (like lecithin) that allow oil droplets to be dispersed and stabilized in the water-based vinegar, forming an emulsion (a type of colloid) so the mixture doesn't separate.