Emulsifiers are liaisons between the two liquids and serve to stabilize the mixture. Eggs and gelatin are among the foods that contain emulsifiers. In mayonnaise, the emulsifier is egg yolk, which contains lecithin , a fat emulsifier. Small particles like this do not settle out and will pass right through filter paper. The particles in a colloid can be solid, liquid or bubbles of gas.
Emulsions are liquid-liquid colloids, tiny liquid droplets suspended in another liquid.
Emulsions are usually thick in texture and satiny in appearance. Mayonnaise is made by combining lemon juice or vinegar with egg yolks. Then, oil is added drop by drop as the mixture is rapidly whisked. But, as the sauce begins to thicken, oil can be added more rapidly. Seasonings are whisked in after all of the oil has been added.