Originally published in the Journal de Montréal on April 2, 2011.
Basically, mayonnaise is an emulsion of egg yoke, oil and either lemon juice or vinegar. Other ingredients are sometimes added to enhance the taste.
From a physicochemical point of view, it is a homogeneous mixture of two immiscible liquids (which do not normally mix), that is, oil and the water of lemon juice or vinegar. The egg yoke acts as an emulsifier or stabilizer, because it facilitates the dispersion of oil in water in the form of small droplets that transform everything into a smooth and consistent mass.
It is therefore necessary to bear in mind the chemistry between the ingredients, in order to make a successful homemade mayonnaise. The key factor is the quantity of oil and speed of incorporation. To encourage the stabilizing action of the egg, you can mix a tablespoonful of mustard into it at the beginning and let it rest for 3 to 5 minutes.
Then, add the oil in a steady trickle, briskly whipping all the while. Adding oil thickens the mayonnaise while adding water has the opposite effect. Vinegar or lemon juice is added at the end.
Your mayonnaise is ready when you can draw a line in it and it doesn’t disappear. In theory, you should be able to turn the bowl upside down without the mayonnaise falling out, but I advise you not to try out this technique as it’s a bit too risky…
Try our recipe for Mustard and Garlic Mayonnaise