On food and cooking the science and lore of the kitchen ( PDFDrive ) 44

different story. It is fatal to the fat globule
membrane. Cold milk fat and freezing water
both form large, solid, jagged crystals that
pierce, crush, and rend the thin veil of
phospholipids and proteins around the
globule, just a few molecules thick. If you
freeze milk or cream and then thaw it, much
of the membrane material ends up floating
freeintheliquid,andmanyofthefatglobules
get stuck to each other in grains of butter.
Make the mistake of heating thawed milk or
cream,andthebuttergrainsmeltintopuddles
ofoil.
MilkProteins:Coagulation
byAcidandEnzymes

TwoProteinClasses:CurdandWheyThere
aredozensofdifferentproteinsfloating
aroundinmilk.Whenitcomestocooking
behavior,fortunately,wecanreducethe
proteinpopulationtotwobasicgroups:Little


MissMuffet’scurdsandwhey.Thetwo
groupsaredistinguishedbytheirreactionto
acids.Thehandfulofcurdproteins,the
caseins,clumptogetherinacidconditionsand
formasolidmass,orcoagulate,whileallthe
rest,thewheyproteins,remainsuspendedin
theliquid.It’stheclumpingnatureofthe
caseinsthatmakespossiblemostthickened

milkproducts,fromyogurttocheese.The
wheyproteinsplayamoreminorrole;they
influencethetextureofcaseincurds,and
stabilizethemilkfoamsonspecialtycoffees.
Thecaseinsusuallyoutweighthewhey
proteins,astheydoincow’smilkby4to1.
Bothcaseinsandwheyproteinsare
unusualamongfoodproteinsinbeinglargely
tolerantofheat.Wherecookingcoagulatesthe
proteinsineggsandmeatintosolidmasses,it
doesnotcoagulatetheproteinsinmilkand
cream—unlessthemilkorcreamhas
becomeacidic.Freshmilkandcreamcanbe
boileddowntoafractionoftheirvolume