On food and cooking the science and lore of the kitchen ( PDFDrive ) 207

theoutset,inordertoobtainaveryfirm,
densefoam.
ASilverBulletfortheCopperTheory
Why do copper bowls make more stable
egg foams? I’ve wondered about this for
many years. In 1984 I did some
experiments with the help of Stanford
Universitybiologists,andthenpublisheda
theoryintheBritishsciencejournalNature
and in the first edition of this book. The
experiments suggested that one of the
albumen proteins, ovotransferrin, takes up
copper from the bowl surface and is
thereby rendered resistant to unfolding —
which could make the foam as a whole
resistant to overcoagulating. That theory
stood up for ten years, until one day on a
whim I tried whipping egg whites in a
silver-plated bowl. Ovotransferrin doesn’t
bindsilver,sothefoamshouldhaveturned
grainy. It didn’t. It remained light and


glossy.Iresumedmyfrothyinvestigations,
andlearnedthatbothcopperandsilverdo
block sulfur reactions between proteins.
Hence the revised edition of the copper
theoryoutlinedhere.
WaterWaterisseldomcalledfor,butin
smallamountsitincreasesthevolumeand
lightnessofthefoam.Becausewaterthinsthe

whites,however,it’smorelikelythatsome
liquidwilldrainfromthefoam.Albumen
dilutedby40%ormoreofitsvolumeinwater
cannotproduceastablefoam.
BasicEgg-BeatingTechniques

Beatingeggwhitesintoafoamisoneofthose
techniquesaboutwhichcooksandcookbooks
waxsternandstringent.Infactit’snotallthat
sensitivetodetails.Justaboutanyeggand
bowlandwhiskcangiveyouagoodfoam.
ChoosingtheEggsAneggfoambeginswith