Why wouldn't heated egg yolks thicken?

March 8, 2006 2:15 PM

Recently I failed to make a lemon tart because the eggs wouldn't thicken. What went wrong?

What would cause two eggs, three egg yolks, and organic sugar heated in a Pyrex cup in a frying pan of simmering water not to thicken in the slightest? Eventually the water evaporated and I gave up.

Someone suggested that use of a silver fork as a whisk somehow catalyzed the protein coagulation reaction, causing it to fail. Does that make sense?

BTW, I'm a pretty good cook, and have made the tart successfully many times. I've read a lot about cooking, including McGee, and didn't see anything helpful there.

Thanks in advance.

posted by phhht to Science & Nature (9 answers total)

Well, you might trying putting a bit of cream of tartar in there next time. Or is that only for egg whites?
posted by borkingchikapa at 2:34 PM on March 8, 2006

I was going to say that you didn't wait long enough--every time I've made a curd, it has taken WAY longer than a recipe states--but if you've made the exact recipe before using the same technique (pyrex cup IN a frying pan? That's a new one on me) I dunno.

I'm thinking specifically of a curd from Cook's Illustrated that took 30 minutes rather than 10, and the !*@&*(@#$ grapefruit meringue pie from a recent Food & Wine that took an hour instead of 15 minutes. Not that I'm bitter or anything.

Cream of tartar won't make cooking eggs thicken; it just helps hold the "bubbles" in whipped egg whites together, right?
posted by bcwinters at 2:54 PM on March 8, 2006

You've used this technique before? Per bcwinters' comment, a Pyrex cup might insulate too much to let enough heat through. A metal bowl in boiling water would probably work better.
posted by GuyZero at 3:27 PM on March 8, 2006

Sugar increases the temperature needed to create a gel. (coagulation) If you used too much, it could have prevented coagulation altogether. Yolks have a higher coagulation temperature than whites, so try using additional egg whites. Acids like cream of tartar produce a firmer gel and lower the coagulation temperature, making the process faster.
posted by azuma at 3:32 PM on March 8, 2006

I wonder if the eggs were too fresh? I've gotten eggs directly from the 'farmer' (actually a hobbyist with a few hens), and while they tasted great, they did cook up differently than store-bought. I wasn't making a curd with them or anything, though...
posted by Bron at 3:35 PM on March 8, 2006

egg whites whip up higher in a copper bowl scroll way down
posted by hortense at 4:12 PM on March 8, 2006

I think you didn't get it hot enough. Using a double boiler is nice, but I think you really have to have a good conducting inner pan and a lot of roiling water outside.
This recently happen to my wife with a lemon merenge pie, it didn't set at all. I removed the filling and brought it to a boil in a regular pan the next day and it set up. Here's my blog post on it.
posted by 445supermag at 5:33 PM on March 8, 2006

Response by poster: I felt sure that with enough time and heat, the eggs would have to scramble. After 45 minutes, before I quit but after I gave up, I increased the heat a lot - no dice. I used the same amount of sugar as always, and the eggs were not too fresh.

Well, thanks anyway. It'll probably work fine next time. If I could figure this out, I could probably patent it.
posted by phhht at 8:21 PM on March 8, 2006

Pure idle speculation here, but could weather conditions have been a contributing factor? The 'wrong weather' can affect things like candy making or mayonnaise from scratch. Also a factor that could make the same recipe give different results on different days.
posted by gimonca at 6:36 AM on March 9, 2006