On Food and Cooking

Saturated and unsaturated fatty acids. An
unsaturated fatty acid has one or more double
bonds along its carbon chain, and a rigid kink
at that point in the chain. The structural
irregularity caused by the double bond makes
it more difficult for these molecules to solidify
into compact crystals, so at a given
temperature, unsaturated fats are softer than
saturated fats. In the hydrogenation of
vegetable oils to make them harder, some cis-
unsaturated fatty acids are converted to trans-
unsaturated fatty acids, which are less kinked
and behave more like a saturated fatty acid,
both in cooking and in the body.
Fat Saturation and Rancidity Saturated fats
are also more stable, slower to become rancid
than unsaturated fats. The double bond of an