Agriculture Reference
In-Depth Information
First, you need to understand a little egg chemistry. Eggs are full of strands of protein that
at room temperature are tightly curled and separate. As they heat up, the protein strands
relax and unfold. As they unfold, they bump into other protein strands and link up, cap-
turing the liquid that is present in the egg. This is called coagulation. Typically, with pure
egg, the white begins to set between 145 and 150 degrees and is firm at 160 degrees. By
180 degrees the protein strands have tightened to the point that all the liquid is wrung out.
(Egg proteins are not alone in this behavior; that's what happens when you overcook a
chicken breast, too.)
That 145-to-160-degree window is pretty hard to hit, especially over a live flame, which
is precisely why perfectly scrambled eggs are such a miracle. Add sugar, however, and an
interesting thing happens. The window opens wider. The sugar isolates the protein strands,
moving them farther from each other and keeping them apart longer. This raises the tem-
perature at which they coagulate. Cooks have been taking advantage of this chemical re-
action for centuries. The phenomenon is the secret behind both cooked custards and za-
baglione, the Italian dessert consisting of egg yolks, sugar and, traditionally, Marsala that
is beaten and cooked until it is a slightly foamy cream.
In fact, if you take zabaglione, replace the liqueur with lemon juice and add butter, you
have lemon curd.
But there are lemon curds and there are lemon curds. To come up with the version I liked
best, I first analyzed a dozen recipes from different cookbooks. Although the techniques
were basically the same, the proportions of ingredients varied greatly. Some recipes, for
instance, called for whole eggs, some for yolks and some for a combination of the two. I
made curds with pure yolks and with an equal volume of whole eggs and compared them.
Both methods worked equally well, but there were major differences in the outcomes.
Made with yolks, the curd was stiffer and the flavor richer and more custardy. Made with
whole eggs, the curd was lighter-colored, the set was softer, and the flavor was more in-
tensely fruity. I ended up compromising, using 2 whole eggs and 2 egg yolks to give the
curd a slightly smoother flavor and slightly firmer set.
The amount of sugar in the recipes varied even more, ranging from Yz cup to 1 cup. A re-
cipe I made with 1/2 cup of sugar was well balanced. I tried 3/a cup and found that it was
too simply sweet, particularly in the aftertaste. I never added as much as 1 cup of sugar.
Butter amounts varied from 2 tablespoons to 8 tablespoons. I found that the amount of
butter resulted in much more subtle differences than the amount of sugar. Curd made with
only a little butter was more tart and fruity. The more butter I added, the more complex
