FoodBanter.com - View Single Post - Fat Substitute, Once Praised, Is Pushed Out of the Kitchen

On Tue, 15 Feb 2005 00:03:36 -0000,
(Alex Rast) wrote:

>at Mon, 14 Feb 2005 05:22:27 GMT in <q4d011tgs6ds56fbbtc88r9snoheld18pn@
>4ax.com>, (Bob) wrote :
>
>>On Mon, 14 Feb 2005 04:33:03 -0000,
>>(Alex Rast) wrote:
>>
>>>
>>>>I don't know why they don't use *fully* hydrogenated vegetable oil. It
>>>>does not contain any trans- fats, just saturated fats and maybe a little
>>>>monounsaturateds.
>>>
>>>AFAIK, fully hydrogenated fats still contain large amounts of trans fats
>>>because it's a by-product of the hydrogenation process.
>>
>>By definition, there is no trans fat in fully hydrogenated fat. Trans
>>fat is a byproduct of _partial_ hydrogenation. If hydrogenation is
>>complete, there is no unsaturation, cis or tarns.
>
>It is my understanding that both terms: cis- and trans-fats, apply to
>saturated fats. It's simply a difference in molecular configuration.
>

No. Cis and trans refer to the molecular configuration at unsaturated
points. They have no meaning with saturation.

Have you seen the structure of a fatty acid? There are always many
points of saturation, and, if relevant, a small number of
unsaturations.

Briefly, without a picture, cis means that the 2 H at an unsaturation
point in the same direction, whereas trans means they point in
opposite directions. With saturations, the molecule can rotate freely,
around the C-H bond, so this would not mean anything. A cis
unsaturation results in a kink in the structure, which is why the
(normal) cis-unsaturated fats tend to be liquids. That is, the kink
prevents them from lining up well.

>>> The hydrogenation process is, essentially,
>>>more indiscriminate about how it saturates the hydrogen-carbon bonds.
>>
>> Hydrogenation involves saturating (adding hydrogen
>>to) C=C bonds, not C-H.
>
>I was talking about the positions where C-H bonds form. Naturally, you
>wouldn't (couldn't) try to add something to a C-H bond because hydrogen has
>only 1 electron to share. In the phrase "saturates the H-C bonds", I meant
>how (and where) it adds new H-C bonds.

ok. But note that trans-ness (did I just invent a word?) does not come
from indiscriminate addition of H-H; it comes from a reversal of the
reaction. Trans unsaturation is a bit more stable than cis. In other
words, hydrogenation is rather indiscriminate but that is not what is
relevant here. What matters is that it is reversible.

bob