On food and cooking the science and lore of the kitchen ( PDFDrive ) 591
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sweetpotatotoEurope,andbytheendofthe
15thcenturyitwasestablishedinChinaand
thePhilippines.Chinanowproducesand
consumesfarmoresweetpotatoesthanthe
Americas,enoughtomakeitthesecondmost
importantvegetableworldwide.Thereare
manydifferentvarieties,rangingfromdryand
starchyvarietiescommonintropicalregions,
somepaleandothersredorpurplewith
anthocyanins,tothemoist,sweetversion,
darkorangewithbeta-carotene,thatispopular
intheUnitedStatesandwasconfusingly
nameda“yam”in1930smarketing
campaigns(fortrueyams,seep.306).The
bulkoftheU.S.cropisgrownintheSoutheast
andcuredforseveraldaysat86ºF/30ºCto
healdamagedskinandencouragesugar
development.Truetotheirsubtropical
heritage,sweetpotatoesstorebestat55–60ºF/
13–16ºC.Chillinginjurycancontributeto
“hardcore,”aconditioninwhichtheroot
centerremainshardevenwhencooked.
Mostsweetpotatovarietiessweetenduring
cookingthankstotheactionofanenzymethat
attacksstarchandbreaksitdowntomaltose,a
sugarmadeupoftwoglucosemolecules
that’saboutathirdassweetastablesugar.
Moistor“soggy”varietiesconvertasmuchas
75%oftheirstarchtomaltose,sotheyseem
permeatedwithsyrup!Theenzymestartsto
makemaltosewhenthetightlypackedstarch
granulesabsorbmoistureandexpand,
beginningaround135ºF/57ºC,anditstops
whentherisingheatdenaturesit,ataround
170ºF/75ºC.Slowbakingthereforegivesthe
enzymealongertimetoworkthandoesrapid
cookinginsteam,boilingwater,ora
microwave,andproducesasweeterresult.
Freshlyharvested“green”rootsavailablein
theautumnhavelessenzymeactivityandso
don’tbecomeassweetormoist.
Paleandred-purplesweetpotatoeshavea
delicate,nuttyaroma,whileorangetypeshave
theheavier,pumpkin-likequalitycreatedby
