Which component in egg yolk is known to help emulsify?

Lecithin is the correct answer because it is a phospholipid found in egg yolk that serves as an effective emulsifier. Emulsification is the process of mixing two immiscible liquids, such as oil and water, in which one is dispersed throughout the other. Lecithin has both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties, allowing it to stabilize the mixture by surrounding the oil droplets, preventing them from coalescing and separating from the water phase.

The other options do not possess emulsifying properties to the same extent as lecithin. Cholesterol, while present in egg yolk, is a sterol and does not function as an emulsifier. Casein is a protein found in milk that can stabilize emulsions in dairy products but is not present in significant amounts in egg yolks. Albumin, which is the main protein in egg whites, provides structure and can contribute to foaming but does not act as an emulsifier like lecithin does in the yolk.