On Food and Cooking

Ovalbumin, the most plentiful egg
protein, was the first protein ever
crystallized in the laboratory (in 1890),
yet its natural function remains unclear.
It seems related to a family of proteins
that inhibit protein-digesting enzymes,
and may be a mainly nutritional relic of
ancient battles against a now-extinct
microbe. It is the only egg protein to
have reactive sulfur groups, which make
decisive contributions to the flavor,
texture, and color of cooked eggs.
Interestingly for the cook, ovalbumin’s
heat resistance increases for several days
after laying, so that very fresh eggs need
less cooking for a given consistency than
eggs a few days old.
Ovotransferrin holds tightly onto iron
atoms to prevent bacteria from using
them, and to transport iron in the
developing chick’s body. It is the first
protein to coagulate when an egg is