On food and cooking the science and lore of the kitchen ( PDFDrive ) 230

ThoughtheaverageChineseconsumesonlya
thirdasmanyeggsastheaverageAmerican,
andthoughmostofthoseeggsarechicken
eggs,Chinaisrenownedforitspreserved
duckeggs,includingthe“thousand-year-old”
eggs.Theseandplainsalt-preservedeggs
comefromtheduck-richsouthernprovinces,
wheretheymadeitpossibletotransporteggs
todistantmarketsandstorethemformonths
duringtheoffseason.Theproteinsand
membranesofchickeneggsarelesssuitedto
someofthesetreatments.
Salted Eggs The simplest method for
preserving eggs is to treat them with salt,
which draws the water out of bacteria and
moldsandinhibitstheirgrowth.Theeggsare
immersed in a 35% salt solution, or coated
individually with a paste of salt, water, and
clay or mud. After 20 or 30 days, the egg
stops absorbing salt and reaches chemical
equilibrium. Strangely, the white remains


liquid, but the yolk at its center becomes
solid.Thehighlevelsofpositivesodiumand
negative chloride ions actually shield the
albumen proteins from each other, but cause
theyolkparticlestoagglomerateintoagrainy
mass.Saltedeggs,whicharevariouslycalled
hulidanandxiandan,areboiledbeforethey’re
eaten.

Fermented EggsA second kind of preserved
egg, little seen in the West, is made by
covering gently cracked eggs in a fermenting
mass of cooked rice or other grains mixed
with salt: in essence a concentrated and salty
versionofsakeorbeer.Zaodanmatureinfour
tosixmonthsandtakeonthearomatic,sweet,
alcoholic flavor of their surroundings. Both
white and yolk coagulate and fall out of the
softenedshell.Sucheggscanbeeatenasisor
cookedfirst.
Pidan: “Thousand-Year-Old”Alkali-Cured
Eggs The most famous of preserved eggs are