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Independent Weekly
March
13, 2003
Dairy
diet can boost beneficial CLAs
by
Denise Aminot-Gilchrist, MSc student in the Department of
Food Science
Milk and
dairy products have long been considered an important part
of the North American diet. They provide essential nutrients
such as protein, calcium, vitamins, minerals and energy. In
recent years, medical research has shown that milk and milk
products also possess a group of fatty acids with potent anticarcinogenic
properties referred to as CLAs.
Conjugated
linoleic acids (CLAs) are predominantly found in products
of ruminant animal origin with milk being the richest source.
On average, milk contains 0.55 % CLA. Ground beef contains
0.43 % and vegetable oils, including canola, corn and olive
oil, only contain trace amounts (0.02 % CLA). In addition
to their anticarcinogenic properties, milk and dairy products
have also been reported to have functions in reducing body
fat, preventing atherosclerosis and modulating the immune
system. Thus, CLAs provide another good reason for consuming
milk and milk products in our daily diet. Ironically, these
findings were discovered at a time when the nutritional focus
has been to remove or reduce the fat levels in milk and dairy
products!
Because dairy products high in CLAs have tremendous potential
within the emerging nutraceutical and functional food markets,
there's a growing interest in CLA related research work across
Canada. Milk CLA is produced by ruminal microorganisms during
the digestion of long-chain polyunsaturated fatty acid in
a dairy cow's rumen. It is also synthesized endogenously in
tissues from a precursor of ruminant origin. Thus, factors
that alter the rumen ecosystem and ultimately ruminal digestion,
such as a dairy cow's diet, seasonal variations, animal breed
and age, also affect CLA levels in milk. Numerous studies
have shown that supplementing a dairy cow's diet with feed
sources high in unsaturated fats increase CLA levels in milk
fat. Past studies also suggest that processing may influence
CLA formation in dairy products.
I have
worked at the University of Manitoba with Dr. Arnie Hydamaka
in the Department of Food Science investigating the effects
of processing CLA-enhanced milk and the subsequent storage
of products made from this milk. This study was performed
in collaboration with Dr. Karen Wittenberg from the Department
of Animal Science who fed cows a special formulated diet to
provide milk with CLA values 10 to 15 times greater than those
typically found in milk.
On average,
we found that the CLA content of experimental unprocessed
milk ranged between 1.5-2.6% of the total fatty acid compared
to 0.4% normally found in commercial milk. The question to
be answered was whether this high CLA level could be maintained
or enhanced through processing. Milk obtained from cows fed
CLA promoting diets was processed into pasteurized milk, yogurt,
cheddar cheese, feta cheese, Queso Blanco cheese, butter,
kefir and cultured cream at the University of Manitoba's dairy
pilot plant facility.
Our research
indicated that most processing technologies such as heat treatments
and cultures had no substantial effect on CLA levels in dairy
products. We also found that the CLA levels in all dairy products
manufactured remained stable during storage or aging periods.
Furthermore, our sensory evaluation data was positive, indicating
that consumers would accept the high CLA products.
Our research
provides conclusive evidence that CLA-enhanced dairy products
can be manufactured and stored without significant loss of
CLAs. These findings are beneficial for both the consumer
and dairy industry. Dairy products high in CLA will allow
consumers to obtain the therapeutic health benefits of CLA
by consuming a natural food product. This will also position
the dairy industry as an important contributor to the newly
created nutraceutical/functional food industry.
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