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MU researchers are discovering
how to add beneficial bacteria to soy products, which will
improve soy’s health advantages. Fred S. Witte photo
courtesy of USDA
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Scientists
Increase the
Health Value of Soy
By Jeremy Diener
Using a variety of tests, including a simulated
human colon, University of Missouri-Columbia researchers have
shown that probiotic, or beneficial, bacteria can thrive in unfermented
soy milk products, a discovery that could lead to new soy-based
health products available for consumers.
Probiotic bacteria have been shown to prevent
intestinal infections, lower serum cholesterol, express anti-cancer
activities and stimulate the immune system, said Azlin Mustapha,
MU associate professor of food
science in the College
of Agriculture, Food and Natural Resources.
Until now, probiotic bacteria supplements
have been added only to fermented soy products, such as soy yogurts,
soy cheeses and cultured soy drinks. However, other bacteria used
to start the fermenting process can have an adverse effect on
the beneficial bacteria, dramatically reducing its effectiveness.
In order for probiotic bacteria to be beneficial, they must remain
alive and in large numbers within the human body.
Unfermented soy products, such as soy milk
and tofu, are widely available in grocery stores, yet none have
been commercially available containing probiotic bacteria. To
address this, Mustapha added probiotic bacteria to unfermented
soy milk and fed it into a bench-top model fermenter designed
to mimic the human stomach, small and large intestine. The simulated
digestive tract included artificial gastric and intestinal juices
to recreate the digestive process, and allowed the researchers
to observe probiotic bacteria counts before and after.
“High enough numbers of the probiotics
survived at the end of the gastrointestinal simulation to potentially
generate desired health benefits,” Mustapha said.
The probiotic strains used in her study, Lactobacillus
paracasei and Bifidobacterium longum, significantly decreased
concentrations of undesirable fecal enzymes that are involved
in certain cancers. Results also showed increases in concentration
of some short chain fatty acids, which are important energy sources
to intestinal cells and help to inhibit undesirable bacteria from
proliferating in the intestines. The probiotic bacteria also resulted
in high antimicrobial effects on clostridia and Bacteroides, which
are potentially undesirable bacteria found in the colon. Similar
observations were found with mice fed a diet of these probiotic-fortified
soy beverages for 15 days.
In a second study using fermented soy products,
two probiotic bacteria, Lactobacillus paracasei and L. rhamnosus,
were used to replace one of the traditional yogurt starters, L.
bulgaricus, in a soy yogurt-like product, which was refrigerated
for 30 days. The probiotic bacteria were maintained in significantly
higher numbers than in the traditional yogurt starter at the end
of the refrigerated storage.
Taste tests performed using trained sensory
panelists, revealed that the soy yogurts fermented with the probiotic
lactobacilli were very similar in taste to those fermented with
traditional starter bacteria.
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Last Update:
November 15, 2007
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