Due to the many failed attempts at making good mayonnaise sauce at home, I was a little wary about making it yesterday. I thought for a while about what could've gone wrong, and decided to do a bit of searching on the internet for the answer.

I was surprised by the answer: Lemon. By composition, mayonnaise is an emulsion of lemon juice and oil; with egg yolk acting as an emulsifying agent. How Stuff Works has a good write-up about this.

I've never added lemon before, and thus I always used to get frothy, oily goop that used to taste remotely like mayo, but was nothing like the tasty, creamy spread I got yesterday. Here's a detailed recipe. There's also a low-fat, and looking at the ingredients, probably low-taste substitute for mayonnaise for all you health concious people.