Eggs in Bread

Eggs

Whole eggs are about 75% water, so, as with milk, bakers must be careful not to
simply substitute one for the other. Whole eggs are net tougheners, which means
that, although the yolk contains fat, enough proteins are present in eggs to more than
compensate for any tenderizing effects in the yolk.

ADD STRENGTH

Whole eggs typically are included in a bread formula to add strength to dough,
together with a bit of color and flavor. If strength is all you want, then egg whites
may be added alone, or you can use separated egg yolks to add richness and color
to the bread crumb. Whole eggs and egg yolks are also useful in another way—as
emulsifiers. Lecithin is a natural emulsifier in egg yolks that holds added fat in suspension
with the moisture in dough. This is especially important in high-fat breads
like brioche.

(from "Bread Baking: an artisan's perspective")