On Food and Cooking

saturated fat; the trans unsaturated fats
contribute a great deal to margarine
firmness. Trans unsaturated fats are also
less prone to oxidation or heat damage and
make cooking oils more stable.
Trans fatty acids have come under
scrutiny due to the likelihood that they
may contribute to human heart disease.
Research has shown that they not only
raise undesirable LDL cholesterol levels in
the blood as saturated fats do, they also
lower desirable HDL levels. Manufacturers
are now modifying their processing
methods to lower trans fatty acids levels in
U.S. margarines and cooking oils from the
present levels, which reach 20–50% of
total fatty acids in hard margarines (less in
softer products).
Margarine manufacturers are not the
only producers of trans fatty acids: the
microbes in animal rumens are too! Thanks
to their activity, the fat in milk, butter, and