Acido Linolenico

Survey of the Conjugated Linoleic Acid Contents
of Dairy Products
H. LIN, T. D. BOVLSTON,1 M. J. CHANG, L. O. LUEDECKE,
and T. D. SHULTZ
Department of Food Science and Human Nutrition
Washington State University
Pullman 99164-6376
ABSTRACT

The objective of this research was to
determine the content of conjugated
linoleic acid, an anticarcinogen, in dairy
products. Fifteen cheeses,three fermented dairy products (other than
cheeses), and four fluid milk products
(two brands for each product) were included in the survey. Total lipids, fatty
acids, protein, moisture, and titratable
acidity were also measured to determine
the relationship between the content of
these constituents and conjugated
linoleic acid content.
The conjugated linoleic acid content
of cheeses rangedfrom 3.59 to 7.96 mgl
g of lipid. Blue, Brie, Edam, and Swiss
cheeses had significantly higher conjugated linoleic acid content than the
other cheeses. Sharp Cheddar cheeses
tended to have higher conjugated linoleic
acid content than the medium Cheddar
cheeses, but the increase was not significant. The conjugated linoleic acid content of the other fermented dairy
products ranged from 3.82to 4.66 mglg
of lipid, and cultured buttermilk had the
highest content. The conjugated linoleic
acid contents of four fluid milks ranged
from 3.38 to 6.39 mglg of lipid and were
not significantly different from one
another. Multiple linear regressions of
conjugated linoleic acid content and the
total fatty acid content indicated a relationship between conjugated linoleic acid
content andthe content of precursors and
intermediates of conjugated linoleic acid

Received October 7, 1994.
Accepted May 8, 1995.
lConesponding author.
1995 J Dairy Sci 78:2358-2365

formation, including linoleic and oleic
acids.
(Key words: conjugated linoleic acid,
anticarcinogen, lipids)
Abbreviation key: CLA = conjugated linoleic
acid, LA = linoleic acid.
INTRODUCTION

Conjugatedlinoleic acids (CLA) are a mixture of octadecadienoic acids that have been
recently recognized as anticarcinogens. These
compounds are linoleic acid (LA) derivatives
with cis-9, trans-ll-; trans-9, cis-ll-; trans-9.
trans-ll-; trans-1 0, trans-12-; and trans-lO,
cis-12-octadecadienoic acids accounting for the
major isomers and cis-9, cis-ll-; cis-l0, cis12-; cis-l0, trans-12-; and cis-ll,cis-13octadecadienoic acids accounting for minor
isomers (12, 25). An anticarcinogenic compound, first isolated from ground beef by Pariza et al. (17) in 1983, was later identified as
CLA (11, 13). The anticarcinogenicity of CLA
has been demonstrated in rats, mice, and human cancer cells (11, 13, 14, 16, 21, 22). The
cis-9, trans-ll isomer is assumed to be the
most important CLA isomer in terms ofanticareinogenic activity because it was the only
isomer incorporated into the phospholipid fraction of rat tissues when those rats were fed a
mixture of CLA isomers (13, 14).
Conjugated LA is widely found in many
foods, including dairy products (4, 12, 18, 25),
meats (4, 8, 11, 16), certain vegetable products
(1,4, 8), and some infant foods (4). Contents of
CLA in animal products are muchhigher than
in plant oils. Among the animal products, CLA
contents are generally higher in ruminant tissues than nonruminant tissues, and dairy
products are recognized as major dietary
sources of CLA. The CLA contents of most
dairy products range from 2.5 to 7.0 mglg of
lipid. Nonfat frozen dairy dessert and nonfat
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SURVEY OF CONJUGATFD LINOLEIC ACID

yogurt have relatively low CLAcontents at .6
and 1.7 mglg of lipid, respectively (4).
Conjugated LA formation in dairy products
has been proposed to occur through the
isomerization of LA and linolenic acids in the
rumen and through oxidation of LA by free
radicals during processing (12). Biohydrogenation of LA and linolenic acids to stearic acid in
the rumen through microbial enzymatic reactions also contributes to...