On food and cooking the science and lore of the kitchen ( PDFDrive ) 206

Eggwhitefoamsarealmostalwaysmadewith
otheringredients,andthesecaninfluencethe
beatingprocessandthefinalconsistency.
Salt Salt increases the whipping time and
decreases the foam’s stability. Salt crystals
dissolve into positively charged sodium and
negatively charged chloride ions, and these
probably compete for bonding sites on the
unfolded protein molecules, thereby reducing
the number of protein-protein bonds and so
weakeningtheoverallstructure.It’stherefore
best to add salt to the other components of a
dish — the base of a soufflé, for example —
ratherthantothefoamitself.
Sugar Sugar both hinders and helps foam
making.Addedearlyintheprocess,itdelays
foaming, and it reduces the foam’s ultimate
volume and lightness. The delay comes from
sugar’s interference with the unfolding and
bondingoftheproteins.Andthereductionin
volumeandlightnessiscausedbythesyrupy


sugar-eggmixturebeinghardertospreadinto
thin bubble walls. Slow foaming is a real
disadvantagewhenthewhitesarewhippedby
hand — at standard soft-meringue levels, it
doublesthework—butlesssoifyou’reusing
astandmixer.
Thehelpfulthingaboutsugaristhatit
improvesthefoam’sstability.Bymakingthe

liquidthickandcohesive,sugargreatlyslows
drainagefromthebubblewallsand
coarseningoftexture.Intheoven,the
dissolvedsugarhangsontothewater
moleculesandsodelaystheirevaporationin
thehighheatuntilafterovalbuminhashad
timetocoagulateandreinforcetherawfoam.
Anditeventuallycontributesreinforcementof
itsownintheformoffinebutsolid,cottoncandy-likestrandsofdrysugar.
Sugarisusuallyincorporatedintotheegg
whitesafterthefoamhasbeguntoform,when
manyproteinsarealreadyunfolded.Forsome
purposes,cookswillmixsugarandwhitesat