On food and cooking the science and lore of the kitchen ( PDFDrive ) 1210

typicallyjust0.1%oftheliquidweight(1
gramperquartorliter).
Stabilizing Foams A liquid that is even
modestly supplied with proteins or yolk
phospholipids will form an impressive mass
of bubbles, solid enough to stand up without
flowingorevenslumping.However,thefoam
maystillcollapsewithinaminuteortwo.Air
and water have very different densities, so
whenthefoamislefttostandonitsown,the
airbubblesrisewhilegravitypullstheliquid
in their walls in the opposite direction. This
means that liquid drains from the bubble
walls, which also lose water to evaporation.
Eventually, the foam at the surface becomes
dry, around 95% air and just 5% liquid, the
bubble walls become too thin, fail, and the
bubblespop.
Thisinstabilityofthefoamasawholecan
bepreventedbythesamematerialsthat
stabilizetheemulsifiedsauces:namely


materialsthatinterferewiththefree
movementofwatermolecules,andthereby
slowthedrainageandthinningofthebubble
walls.Foamstabilizersincludethe
microscopicparticlesinpurees,proteins,
thickeningcarbohydrateslikestarch,pectin,
andgums—andevenemulsifiedfat.Freefat
oroilisafoamkiller,becausethefatspreads

attheinterfacewiththeair—it’schemically
morecompatiblewithairthanwithwater—
andpreventsemulsifiersfromsettlingatthe
interfaceandstabilizingit.However,ifthefat
isemulsified—forexampleinaneggyolkor
yolk-basedsauce—thenitremainsdispersed
inthewaterphase,anditsdropletsonly
interferewiththeflowofliquidfromthe
bubblewalls.
Heat-Stabilized Foams: Sabayons Both the
method and the name of the French sabayon
derive from the Italianzabaglione, a sweet,
winyfoamofeggyolks(p.113).Thoughrich