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Trans Fatty Acids

With FDA’s proposed rules on labeling trans fatty acids, there is much interest in the subject. Most vegetable oils, including cottonseed oil, are trans fat free in their natural state. Cottonseed oil is a good choice for many applications where a non hydrogenated oil with good stability is desired.

What are they?

Trans fatty acids are the trans isomers of unsaturated fatty acids. Most naturally occurring unsaturated fatty acids are found in the "cis" form. "Cis" and "trans" refer to the position of the hydrogen atoms around the double bonds of the fatty acids in an oil molecule. When the hydrogen atoms are on the same side of the carbon chain, they are in the "cis" position; those on opposite sides of the chain are in the "trans" position. Oleic acid is an example of a "cis," while elaidic acid is an example of a "trans." "Cis" fatty acids have a kink in them and "trans" fatty acids are straight.

If the triglyceride being examined has a high level of trans fatty acids, they will pack together tightly and solidly forming hard crystals. Harder fats have a higher melting point. The melting points of trans fatty acids are closer to the saturated form than the unsaturated "cis" form.

The majority of the trans fatty acids in the diet are those produced during hydrogenation. When oils are partially hydrogenated from polyunsaturated to monounsaturated, trans fatty acids result. Saturated fat is a much more stable molecule than an unsaturated one; therefore hydrogenation increases the stability of a fat.

Trans fatty acids are not simply the product of man's chemistry. They also occur naturally and may be found in butter, for example. Fats from ruminants, such as cattle and sheep, commonly contain them. Even though there is debate over the average consumption of trans fatty acids (estimates range from 7.6 to 15.2 grams per person per day in the U.S.), there can be no argument that there are many foods that have high levels of trans fatty acids. If the scientific community cannot agree on the quantity of trans fatty acids being consumed, there is an even greater debate about whether these compounds pose potential health risks. Researchers have linked trans fatty acids to everything from heart disease to low birth weights, while other researchers claim the data does not support such claims.

If trans fatty acids are a concern, manufacturers have options to reduce the number of trans fatty acids in their products. In some applications, manufacturers can use a naturally stabile oil, such as cottonseed oil, instead of hydrogenating a less saturated oil, thus avoiding the formation of trans fatty acids. If hydrogenation is needed to achieve a certain functionality, hydrogenating a naturally saturated oil will produce fewer trans fatty acids. Also, if a vegetable oil is hydrogenated to total saturation (less than 3.0 IV), there are no trans fatty acids. Some manufacturers use fully hydrogenated cottonseed oil blended with a highly unsaturated oil to arrive at a blend with near zero trans fatty acids.

Want to know more about oils?

This information was taken from the Guide to Edible Oils published by the National Cottonseed Products Association. A copy may be ordered from the NCPA office.