My understanding is that the two main ingredients of mayonnaise are oil and egg yolks. So why isn’t it yellow in colour?
The short answer to your question is that the yolk is yellow, but you add a LOT of oil, resulting in a pale yellowish emulsion. When finished, the addition of some warm water, or vinegar will actually make it bright white.
I’d like to suggest that in the interest of science you give it a try. One egg yolk (pasturized if desired), about a teaspoon or two of the vinegar of your choice, and some seasoning (garlic, mustard powder). Wisk this really well (or do it with a blender) and then slowly, very slowly, add oil. Drop by drop at first, and then a slight stream once you get it going. One yolk will take about 200ml of oil, or 3/4 of a cup. The mixture should thicken up and have a yellowing tone. The addition of just a few drops of warm water will be surprising–the mixture will turn bright white.
I believe the technical answer you’re looking for is that mayonnaise is an emulsion of oil in vinegar, where the wisking turns the oil into extremely small droplets, eventually becoming opake (sp?). The egg yolk gets so diluted by the oil and denatured by the vinegar that its no longer bright yellow.
Hope this helps. You really should try it, its fun 
Fascinating. I should give it a try.
Ignorance fought. I had always thought that Mayo was egg white.
I suppose there are different ways of making it, but all of the homemade mayo I’ve seen has indeed been yellow. I think it’s more a matter of the mass-produced imitation (Hellman’s, etc.) becoming the standard over time.
I agree. My homemade mayos are always some shade of yellow. Not deep yellow, mind you, but definitely not anywhere near white.
Right, homemade mayo will usually come out as a pale yellowish tinge, and a lot will be determined by the type and amount of vinegar added. Most people add a little bit of mustard or mustard powder which will contribute to the colour. Commercial mayos are also using pasturized egg yolks and chemical emulsifiers that won’t make the mixture as yellow. What’s freaky though, is that with a few drops of warm water it turns bright white.
if it’s pale yellow, your probably not adding enough oil. Personally, I’ve found 200mL to be way to low. Something about twice or 3 times that amound yields a satisfyingly snow white mayo. Egg yolks have an absurb ability to emulsify oils. Something like 17L per egg yolk is the limit IIRC.
Oops, from McGee’s “The Curious Cook”, it’s more like 23 litres.
Holy crap! That’s a lot. (I generally use about 250 ml of oil per yolk. I prefer yellowish mayo, and I like the thickness and silky texture of it at this ratio.)
i’m just here to say that hellman’s is the best mayonnaise ever made, and you will never convince me otherwise, even if you tell me what it’s made of.
i have similar feelings about hot dogs.
Huh. That’s the second time that I’ve recently been reminded of Robert Anton Wilson here.
RAW wrote, with tongue in cheek, about “spooky” synchronicities involving the number 23, expanding Burrough’s obsession to include correlations with the number 17, just for kicks. (“17” has the value of decimal “23” in hex, btw.)
The other time was when I posted this Schroedinger’s Cat reference in the “tenth planet” thread, where the mnemonic for the 10th planet is “mayonnaise.”
Spooooky. 
We now return you to your regular thread, already in progress.
Well, actually, McGee mentions 25 quarts which I converted into litres just because that’s what I’m used to. No synchronicities there… or is there?
I just wanted to mention that when I was a junior in high school, my chemistry teacher had us make mayonnaise in lab, as an example of a colloid (similar to emulsion, smaller particle size). She then sent us around the building to try to get other teachers to sample the results. Even though we’d all brought in bowls and utensils from home to make the mayo, most of the teachers thought we’d made the stuff in the lab beakers, and refused to try any. (It was actually pretty good, although a little more acidic than good ol’ Hellmann’s.)
Do try making it yourself. It’s dead easy, and delicious.
There’s no what that can be correct, 17 or 23L per egg yolk seems insane. I’m currently looking through McGee’s On Food and Cooking, but I haven’t been able to find a specific ratio. I do know that Professional Cooking; for Canadian Chefs, by Wayne Gisslen recommends:
“Add no more than 8 ounces (240ml) oil per large egg yolk, or no more than 1 quart (950ml) per 4 yolks.” (5th Ed. page 575)
Not to challenge you outright but would you mind checking that number again?
As far as making it yourself goes (which I personally have not yet been brave enough to try, partially because I don’t have a food processor yet), Alton Brown on Good Eats does an excellent job explaining how to do it in the episode Mayo Clinic. If you can get ahold of the show to watch, great. However, his recipes are also good.
The mayonnaise I ake myself is alwys bright yellow. However I add mustard, and never ever added warm water. I might try just in order to see if it actually turns white, but is there a point in adding it, taste wise or consistency wise ?
I was told to add it towards the end. You’ll find that as you add more and more oil, the mixture starts to tighten up. At this point you can start to adjust the seasoning and add little bits of more vinegar. If you find that its too thick, especially if you plan to add more oil, you can adjust the consistancy with some warm water. Its really just amazing the transformation that occurs with the addition of just a few drops, not even a teaspoon worth. Again, its all about ajusting the consistancy, since the water obviously isn’t adding flavour, and McGee notes that it ends up watering down the final product.
Hellman’s makes hot dogs?! 