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Apply ultrasound to release b-galactosidase from yogurt bacteria, improving probiotics.

We know that yogurt offers health benefits beyond inherent basic nutrition as it improves lactose absorption in the human gut. Probiotic bacteria are a mixed culture of microorganisms, which, when consumed by humans, affect the host beneficially. Effective yogurt contains at least from 100 to 1000 million live probiotic bacteria per mL. Probiotic yogurt occupies a good marketable position in the dairy marketplace, and there is a clear intent to increase its consumption in the next few years.

A novel sonication technique has been used by Washington State University researchers to rupture yogurt bacteria with the goal of improving the viability of its probiotics. The technique, in which yogurt bacteria are ruptured to release more beta-galactosidase (b-Gal) to improve probiotic viability, will encourage more consumers to buy yogurt.

The investigators worked with two different commercial cultures, YO Mix 236 and DPL ABY 611. The probiotics studied were Lactobacillus acidophilus and Bifidobacterium longum. Physicochemical and rheological characteristics, enzymatic activity, microstructure, and probiotics viability were examined.

The cultures contained Streptococcus thermophilus and Lactobacillus delbruekii ssp. Bulgaricus. They were sonicated using an ultrasonic processor for 3 minutes, 4 minutes and 5 minutes at 16 kHz. A thermocouple in the treatment chamber monitored temperature throughout the testing. The scientists maintained the ultrasound wave constant at 100% for all treatments. Sonicated and unsonicated yogurt samples were used to produce yogurt.

The results demonstrated that probiotics grow better in sonicated yogurt than in unsonicated yogurt, indicating the availability of more nutrients for probiotics due to the greater availability of b-Gal. The viability of probiotics increased by 2 log cycles in sonicated yogurt, compared to just one-half log cycle in unsonicated yogurt. The activity of b-Gal increased because of sonication. This activity increased 4.73 times in sonicated yogurt, compared to 3.28 times in unsonicated yogurt.

Further information. Barry G. Swanson, Department of Food Science and Human Nutrition, Washington State University, FSHN 106K, P.O. Box 646376, Pullman, WA 99164; phone: 509-335-3793; fax: 509-335-4815; email:
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Publication:Emerging Food R&D Report
Date:Feb 1, 2008
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