On food and cooking the science and lore of the kitchen ( PDFDrive ) 1504
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composedofstraight-chainsaturatedfatty
acidsfallintoanorderedsolidstructure—
theprocesshasbeendescribedas“zippering”
—morereadilythandokinkedunsaturated
fats.Animalfatsareabouthalfsaturatedand
halfunsaturated,andsolidatroom
temperature,whilevegetablefatsareabout
85%unsaturated,andareliquidoilsinthe
kitchen.Evenamongtheanimalfats,beefand
lambfatsarenoticeablyharderthanporkor
poultryfats,becausemoreoftheir
triglyceridesaresaturated.
Doublebondsarenottheonlyfactorin
determiningthemeltingpointoffats.Shortchainfattyacidsarenotasreadily“zippered”
togetherasthelongerchains,andsotendto
lowerthemeltingpointoffats.Andthemore
varietyinthestructuresoftheirfattyacids,
themorelikelythemixtureoftriglycerides
willbeanoil.
Saturated and unsaturated fatty acids. An
unsaturatedfattyacidhasoneormoredouble
bondsalongitscarbonchain,andarigidkink
at that point in the chain. The structural
irregularitycausedbythedoublebondmakes
itmoredifficultforthesemoleculestosolidify
into compact crystals, so at a given
temperature, unsaturated fats are softer than
saturated fats. In the hydrogenation of
vegetableoilstomakethemharder,somecisunsaturatedfattyacidsareconvertedtotransunsaturatedfattyacids,whicharelesskinked
and behave more like a saturated fatty acid,
bothincookingandinthebody.
FatSaturationandRanciditySaturatedfats
arealsomorestable,slowertobecomerancid
thanunsaturatedfats.Thedoublebondofan
