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Very often, cis–trans stereoisomers contain double bonds or ring structures. In both cases the rotation of bonds is restricted or prevented. [4] When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas when the substituents are oriented in opposing directions, the diastereomer is referred to as trans.
Reaction scheme: Trans fat is created as a side effect of partially catalytic hydrogenation of unsaturated plant fats (generally vegetable oils) with cis carbon-carbon double bonds. Up to 45% of the total fat in those foods containing human-made trans fats formed by partially hydrogenating plant fats may be trans fat. [52]
"Cis fat" vs. "trans fat" In nature, unsaturated fatty acids generally have double bonds in cis configuration (with the adjacent C–C bonds on the same side) as opposed to trans. [137] Nevertheless, trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep), [138] [139] typically 2–5% of total ...
Each double bond is preceded by a cis- or trans- prefix, indicating the configuration of the molecule around the bond. For example, linoleic acid is designated "cis-Δ 9, cis-Δ 12 octadecadienoic acid". This nomenclature has the advantage of being less verbose than systematic nomenclature, but is no more technically clear or descriptive.
Baking shortenings, unless reformulated, contain around 30% trans fats compared to their total fats. High-fat dairy products such as butter contain about 4%. Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight, [151] but some reformulated ones are less than 1% trans fat.
This creates the trans-2-decenoyl intermediate. Either the trans-2-decenoyl intermediate can be shunted to the normal saturated fatty acid synthesis pathway by FabB, where the double bond will be hydrolyzed and the final product will be a saturated fatty acid, or FabA will catalyze the isomerization into the cis-3-decenoyl intermediate.
The cis bond causes a lower melting point and, ostensibly, also the observed beneficial health effects. Unlike other trans fatty acids, it may have beneficial effects on human health. [ 6 ] CLA is conjugated , and in the United States, trans linkages in a conjugated system are not counted as trans fats for the purposes of nutritional ...
At equilibrium, the trans/cis isomer ratio is about 2:1. Numerous studies have concluded that these trans fatty acids have negative health effects. As a result, many countries have enacted trans fat regulation that aims to eliminate or severely restrict their amount in industrialized food products, such as mandatory labeling of trans fats on ...