On Food and Cooking

Foamed egg whites. The folded proteins in egg
white (left) produce a light, long-lived foam
by unfolding at the interface between liquid
and air, the walls of the air bubbles. The
unfolded proteins then bond to each other,
and form a solid meshwork of reinforcement
around the bubbles (right).
...And Acids There are disadvantages to the
traditional copper bowl: it’s expensive, and a
nuisance to keep clean. (Copper
contamination is negligible; a cup of foam
contains a tenth of our normal daily intake.)
Fortunately there’s a nonmetallic alternative
for controlling reactive sulfur groups. The
sulfur bonds form when the sulfur-hydrogen
(S-H) groups on two different protein
molecules shed their hydrogens and form a