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On food and cooking the science and lore of the kitchen ( PDFDrive ) 152

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Araucanasandbrown-eggbreedsmakeboth
blueandbrownpigmentsandthusgreen
shells.
Thecompletedeggisexpelledbluntend
firstabout25hoursafterleavingtheovary.
Astheeggcoolsdownfromthehen’shigh
bodytemperature(106ºF/41ºC),itscontents
shrinkslightly.Thiscontractionpullsthe
innershellmembraneawayfromitsouter
partneratthebluntendandtherebyformsthe
airspace,whosesizeisanindicatorofegg
freshness(p.81).
TheYolk

Theyolkaccountsforjustoverathirdofa
shelledegg’sweight,anditsbiological
purposeisalmostexclusivelynutritive.It
carriesthree-quartersofthecaloriesandmost
oftheiron,thiamin,andvitaminAoftheegg
asawhole.Theyolk’syellowcolorcomesnot
fromthevitamin-Aprecursorbeta-carotene,


theorangepigmentincarrotsandotherplant
foods,butfromplantpigmentscalled
xanthophylls(p.267),whichthehenobtains
mainlyfromalfalfaandcornfeeds.Producers
maysupplementthefeedswithmarigold
petalsandotheradditivestodeepenthecolor.
Duckyolksowetheirdeeperorangecolor
bothtobeta-caroteneandtothereddish


pigmentcanthaxanthin,whichwildducks
obtainfromsmallwaterinsectsand
crustaceans,egg-layingducksfromfeed
supplements.Oneminorcomponentofthe
yolkthatcancauseamajorculinarydisaster
isthestarch-digestingenzymeamylase,which
hasliquefiedmanyanormal-lookingpie
fillingfromwithin(seep.98).
Spheres Within Spheres That’s a yolk by
numbersandnutrients.Butthere’salotmore
tothisconcentratedpoolofthesun’srays.Its
structureisintricate,muchlikeaChineseset
of nested spheres carved from a single block



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