Food Lipids: Chemistry, Nutrition, and Biotechnology

flame ionization detection. The fatty acid compositions calculated from the MS data
exhibited less average error than the fatty acid determinations using flame ionization
detection data [137].
E. MS-MS
The use of tandem mass spectrometry (MS-MS) has grown considerably in the last
10 years [138,139]. The combination of LC-MS-MS with electrospray ionization is
the most effective current technique for lipid ester analysis [134]. While mass spectrometry
studies the fragmentation pattern of an ionized molecule, MS-MS studies
the fragmentation of a particular fragment ion present in the mass spectrum. Complex
mixtures of fatty acids from bacteria were analyzed by means of GC-MS-MS to
determine double-bond position [140,141].
In one of the more elegant demonstrations of the potential of combining analytical
procedures, silver ion HPLC was used to fractionate the triacylglycerols from
winter butterfat. The fractions were subjected to reversed phase HPLC, MS, and MS-
MS analysis [142,143]. The distribution of cis and trans isomers within each acyl
carbon number of both disaturated monoenoic and saturated dimonoenoic triacylglycerols
was elucidated. In future work this procedure could also be used to determine
the distribution of trans fatty acids in hydrogenated oils.
VI. trans ISOMERS IN COMMERCIAL PRODUCTS
Although the relationship of dietary lipids to human health is a complicated issue
that has sparked some controversy, the importance of controlling fat intake to help
maintain an active and healthy lifestyle has been recognized for many years. Consumer
health concerns about the types and content of dietary fat has resulted in a
great deal of research. trans Fatty acids have received negative publicity in the media
with respect to their effects on serum cholesterol. Several food products have been
reformulated to increase their unsaturated fat and reduce their total fat and trans fatty
acid content.
A. Dietary Recommendations
During the first half of the century, there was little concern about the nutritional
properties of dietary fat. This started to change in the 1950s with epidemiological
studies, which at the time were controversial, linking diets high in animal fats with
the incidence of coronary heart disease [144]. Several studies then indicated the
cholesterol-raising effects of saturated fats and the cholesterol-lowering effects of
polyunsaturated fats [145,146]. Monounsaturated cis and trans fats were considered
neutral. More recently, there have been conflicting reports on the health effects of
trans fatty acids, but little cause for concern [4]. An excellent discussion of the
dietary recommendations for lipids from several sources, including the National
Academy of Science (NAS) and the U.S. Department of Agriculture (USDA), was
recently published [147]. Included was a discussion of the Nutrition Labeling and
Education Act [96]. The trans fatty acid issue is not addressed by the NLEA, but
the regulations authorize the secretary of health and human services to require information
on other nutrients to be added to food labels at a later time. Also, the
preamble to the regulations indicates that data to determine whether consumers
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.