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

identifies as “a copper bowl for beating egg
whites.”Itturnsoutthatalongwithaveryfew
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
foamingeggwhitesessentiallyeliminatesthe
strongest kind of protein bond that can form,
and makes it harder for the proteins to
embrace each other too tightly. Sure enough,
ifyouwhipeggwhitesinacopperbowl—or
inaglassbowltowhichyou’veaddedapinch
of a powdered copper supplement from a
healthfoodstore—thefoamstaysglossyand
never develops grains. A silver-plated bowl
willdothesamething.


Foamedeggwhites.Thefoldedproteinsinegg
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
aroundthebubbles(right).
…AndAcidsTherearedisadvantagestothe
traditionalcopperbowl:it’sexpensive,anda
nuisancetokeepclean.(Copper
contaminationisnegligible;acupoffoam
containsatenthofournormaldailyintake.)

Fortunatelythere’sanonmetallicalternative
forcontrollingreactivesulfurgroups.The
sulfurbondsformwhenthesulfur-hydrogen
(S-H)groupsontwodifferentprotein
moleculesshedtheirhydrogensandforma