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Posted 09.20.04

Beneficial Bacteria Will Boost Soy's Health Advantages, Researchers Say

By Discovering How to Add Beneficial Bacteria to Soy Products, MU Researcher Improves on Soy's Health Advantages

COLUMBIA, Mo. -- 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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