The Fat Speck Myth
Several readers have written in to ask if it’s true that a tiny bit of fat in a mixer bowl will ruin a batch of whipped egg whites. The answer: absolutely not. A small blot of, say, egg yolk will do virtually nothing to impede a batch of whites from whipping up to a nice, voluminous foam.
Egg white foams work because the bubbles that make them up are reinforced by a mesh of string-like protein molecules, molecules which have been coaxed into untangling by the whipping action. At that point they begin to collect around air bubbles because certain regions along their length are attracted to air (are hydrophobic) and others are attracted to water (hydrophilic). Thus the surface of the bubble is a desirable spot for them, as all their different regions are happy, and they can bond to each other side-by-side while they’re there.
Fats are attracted to bubbles for similar reasons. They therefore pose something of a problem for the proteins because they compete for space at the bubble surfaces. Once there, they interfere with the proteins’ ability to bond to one another. However they don’t actually undermine the protein bonding, so if a few lipids are present here and there, it’s no big deal. They don’t bond to one another like proteins do, and once the proteins mesh is formed they can’t really worm their way in (this is why soufflé batters work, because once the egg white foam is formed, you can add plenty of fat without ruining it).
So while you don’t want to ignore fat in your mixer bowl, you shouldn’t freak out about it either. Egg white foams are more forgiving than you might think.
20 thoughts on “The Fat Speck Myth”
Funny. One of the big things I remember from watching the food channel was their insistence on keeping ANY yolks out of the whites. They got me trained to use 3 bowls in case a little yolk got in with the white when separating each egg and then putting that one white in with the others or using it in another way if you messed up. But that way you’d only lose the one egg instead of the whole bowl of whites. Guess I won’t obsess about it as much from now on. Thanks!
I don’t think three bowls is a bad idea per se…just so long as the anxiety is kept to a minimum should a little yolk creep in there! 😉
I did try that method of separating eggs using an empty plastic water bottle. That is amazing and works so well you can pick up the yolk and shake the whites out and never break a yolk with all that handling. I separated 7 eggs in less time than it took to crack them!
Cool! Thanks for the test run!
Now you tell me — after years of throwing out whites if a speck of yolk got in.
Next you’ll be telling me that searing my meat doesn’t lock in the juices.
Thank you so much for this article. I’ve wasted untold numbers of eggs all because a tiny bit of yolk got in with the white while separating. No wonder I love your blog!
My pleasure, Bina, and thanks!
Thanks for that, Joe!
I’m the child of Depression children so I’ve got their strong streak of refusal to waste anything in my DNA. I’ve whipped whites with traces of yolk many times. So when I hear someone intone that there can’t be a TRACE of yolk as though it came from Moses and those stone tablets it makes me crazy.
So little actual cooking and baking takes place in American homes anymore. No one should be intimidating people. Whip your whites! Measure or weigh! Tamper with ingredients! Knead or don’t! If someone’s results are not picture perfect or exactly like the photo in a recipe they may just turn out to be the inventor of the new tuile or the molten something or other.
Bless you, Joe, for supplying so much information about why something does or does not work and what the characteristics of ingredients are that explain why things behave the way they do so we can all go out and experiment and push the boundaries and even throw out a thing or two but never need to be shy about baking with abandon.
That’s my greatest hope for the site, Rainey. Thanks so much for such a generous comment. From the beginning I set out to create a site that would teach something of the “how” of baking, so readers could go off and do things on their own. It’s why I seldom get creative with the presentations. There’s enough to know “under the hood” as it were, and the world is already full of creative recipes. I don’t need to add any more! 😉
Cheers and thanks again,
I don’t know if Joe’s ears were burning last Wednesday but I was telling a friend about his site and mentioned those great points. I sent her the link later and suggested checking it out but warned her this site is addictive!!
Not to mention harmful to the mental health of laboratory animals!
I love this site. Such good information presented in such a sophisticated way. Thanks Joe!
Thank you, Rachel!
I greatly appreciate the compliment!
In my experience flecks of yolks did inhibit my egg white foam… maybe there was too much of it in there?
It definitely depends on the amount, no question. I’m really responding here to the insistence of so many TV cooks that you must practically have a clean room for de-toxing your bowl and implements from egg yolk. Small specks really don’t hurt anything…larger blobs are a different matter, especially if there are only a couple of whites being whipped.
Yeah, the TV cook with initials JC was particularly energetic on this point, in my recollection. Time for a scientific study to see how much egg yolk per white kills peaks!
Excellent idea, Brent! Too bad my daughter’s science fair is over. That would have been perfect!
You were cited by a reader over at Serious Eats and they tested this, too.
They pretty much agreed. A speck of yolk or some oil won’t ruin the meringue, but a few more drops of yolk will.
Thank you for debunking a myth.
Very interesting. And also nice to be mostly-verified via clinical trials! 😉