The right answer is C) They add hydrogen to unsaturated fats.
Trans fatty acids are found in certain products from the industry:
In margarines: to manufacture these products vegetable oils are used which are liquid and partially hydrogenated (partial catalytic hydrogenation). This operation leads to the formation of trans fatty acids, which make it possible to obtain pasty and non-liquid products (the melting temperature of a trans fatty acid is higher than that of its cis isomer), and which is more resistant to oxidation.
In the refined vegetable oils: during the manufacturing process, to deodorize the oils, they are heated up strongly enough for certain compounds (pesticides ...) to be eliminated: this strong heating leads to the isomerization of polyunsaturated fatty acids into trans fatty acids.
Finally, when heating unsaturated fatty substances strongly and durably, this causes the formation of trans fatty acids: the amount of these fatty acids is proportional to the duration and temperature of heating.
