On food and cooking the science and lore of the kitchen ( PDFDrive ) 1507
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— but they have been transformed from an
acutely irregularcis geometry to a more
regulartrans structure (see illustration, p.
799).Cis is Latin for “on this side of,” and
trans for “across from”; the terms describe
the positions of neighboring hydrogen atoms
on the double bond between carbon atoms.
Because the trans fatty acids are less kinked,
more like a saturated fat chain in structure,
they make it easier for the fat to crystallize
and so make it firmer. They also make the
fatty acid less prone to attack by oxygen, so
it’s more stable. Unfortunately, trans fatty
acids also resemble saturated fats in raising
bloodcholesterollevels,whichcancontribute
to the development of heart disease (p. 38).
Manufacturerswillsoonberequiredtolistthe
trans fatty acid content of their foods, and
they’re beginning to implement other
processing techniques that harden fat
consistencywithoutcreatingtransfattyacids.
FatsandHeat
FatsandHeat
Mostfatsdonothavesharplydefinedmelting
points. Instead, they soften gradually over a
broad temperature range. As the temperature
rises,thedifferentkindsoffatmoleculesmelt
at different points and slowly weaken the
whole structure. (An interesting exception to
this rule is cocoa butter, p. 705). This
behavior is especially important in making
pastriesandcakes,andit’swhatmakesbutter
spreadable at room temperature. butter, p.
705).Thisbehaviorisespeciallyimportantin
making pastries and cakes, and it’s what
makesbutterspreadableatroomtemperature.
Meltedfatsdoeventuallychangefroma
liquidtoagas:butonlyatveryhigh
temperatures,from500ºto750ºF/260–400ºC.
Thishighboilingpoint,farabovewater’s,is
theindirectresultofthefats’largemolecular
size.Whiletheycan’tformhydrogenbonds,
thecarbonchainsoffatsdoformweaker
bondswitheachother(p.814).Becausefat
