On food and cooking the science and lore of the kitchen ( PDFDrive ) 204

identifies as “a copper bowl for beating egg whites.” It turns out that along with a very few other metals, copper has the useful tendency to form extremely tight bonds with reactive sul

identifies as “a copper bowl for beating egg whites.” It turns out that along with a very few other metals, copper has the useful tendency

to form extremely tight bonds with reactive sulfur groups: so tight that the sulfur is essentially prevented from reacting with anything else So the presence of copper in foaming egg whites essentially eliminates the strongest kind of protein bond that can form, and makes it harder for the proteins to embrace each other too tightly Sure enough,

if you whip egg whites in a copper bowl — or

in a glass bowl to which you’ve added a pinch

of a powdered copper supplement from a health food store — the foam stays glossy and never develops grains A silver-plated bowl will do the same thing

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