On food and cooking the science and lore of the kitchen ( PDFDrive ) 225

determinedbyprobingtheinteriorwitha
toothpick,andisamatteroftaste;some
peoplelikeacreamyinteriorthatstillclings
tothetoothpick,otherspreferamorefully
cookedconsistency,whichclingstoitselfand
leavesthetoothpickclean.
YolkFoams:
ZabaglioneandSabayons

YolksCan’tFoamWithoutHelpBeatan
eggwhitefortwominutesanditwillexpand
eightfoldintoasemisolidfoam.Beatanegg
yolkfortenminutesandyou’llbeluckyto
doubleitsvolume.Yolksarericherinprotein
thanwhites,andhavetheaddedadvantageof
emulsifyingphospholipidsthatdoafinejob
ofcoatingfatdroplets:sowhycan’tthey
stabilizeairbubblesandmakeadecentfoam?
Oneclueiswhathappenswhenyouwash
outyouryolkybowl:themomentyoupourin
somewater,itfoams!Itturnsoutthatthe


protein-rich,emulsifier-richyolkisdeficient
inwater.Notonlydoesitcontainabouthalf
thewaterthatthewhitedoes,butnearlyallof
itistightlyboundtoalltheothermaterials.In
onetablespoon/15mlofyolk,thevolume
typicalofalargeegg,there’saboutathirdof
ateaspoon/2mloffree,foamablewater.Add
twoteaspoonstogiveitthesamefreewateras

awhite,anditfoamsenthusiastically.
Enthusiasticallybutfleetingly.Putyour
eartothefoamandyou’llhearthebubbles
popping.Theotherdeficiencyoftheeggyolk
isthatitsproteinsaretoostable.Neitherthe
physicalabuseofwhippingnorthepresence
ofairbubblescausestheyolkproteinsto
unfoldandbondwitheachotherintoa
reinforcingmatrix.Ofcourseheatwill,aswe
knowfromhard-boiledyolksandcustards.So
supplementtheyolkwithliquid,andthe
whippingwithcarefulcooking,andthe
mixturewillrisetofourormoretimesits
originalvolume.Exactlythisprocedureisthe