The food lab better home cooking through science ( PDFDrive ) 361
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (65.63 KB, 2 trang )
supersaturated with liquid—there’s more liquid in
there than it can hold on to—so when you slice it
open, all that extra liquid pours out. By resting the
steak,youallowtheliquidthatwasforcedoutofthe
edgesandintothecentertimetomigratebackoutto
theedges.
Seemstomakesense,right?Imagineasteakasa
bigbundleofstraws,representingthemusclefibers,
each straw filled with liquid.As the meat cooks, the
straws start to change shape, becoming narrower
and putting pressure on the liquid inside. Since the
meat cooks from the outside in, the straws are
pinched more tightly at their edges and slightly less
tightlyintheircenters.Sofar,sogood.Logically,if
the edges are pinched more tightly than the center,
liquidwillgetforcedtowardthemiddle,right?Well,
here’s the problem: water is not compressible. In
other words, if you have a two-liter bottle filled to
the brim with water, it is (nearly) physically
impossible to force more water into that bottle
without changing the size of that bottle. Same thing
withasteak.
Unless we are somehow stretching the centers of
the muscle fibers to make them physically wider,
there is no way to force more liquid into them.You
can easily prove that the muscle fibers are not
gettingwiderbymeasuringthecircumferenceofthe
center of a raw steak versus a cooked one. If liquid
werebeingforcedintothecenter,thecircumference
shouldgrow.Itdoesn’t—itmayappeartobulge,but
that is only because the edges shrink, giving the
illusionofawidercenter.Infact,theexactopposite
is the case. Since the center of a medium-rare steak
is coming up to 125°F, it too is shrinking—and
forcingliquidout.Wheredoesallthatliquidgo?The
onlyplaceitcan:outoftheendsofthestraws,orthe
surfaceofthesteak.Thatsizzlingnoiseyouhearas
asteakcooks?That’sthesoundofmoistureescaping
andevaporating.
GiveThatTheoryaRest
So why does an unrested steak expel more juices
than a rested one? Turns out that it all has to do
withtemperature.
We already know that the width of the muscle
fibersisdirectlyrelatedtothetemperaturetowhich
the meat is cooked, and to a degree, this change in
shapeisirreversible.Apieceofmeatthatiscooked
to 180°F will never be able to hold on to as much
liquid as it could in its raw state. But once the meat
hascooledslightly,itsstructurerelaxes—themuscle
fiberswidenupslightlyagain,allowingthemtoonce
again hold on to more liquid. At the same time, as
the juices inside the steak cool, proteins and other
dissolvedsolidscausethemtothickenupabit.Have
you ever noticed that if you leave pan drippings
from a roast to sit overnight, they are almost jellylike?Thisthickeninghelpspreventthosejuicesfrom
flowingoutofthesteaktoorapidlywhenyousliceit.
I cooked a half dozen steaks all to an internal
