Red wine and grape juice inhibit pathogen growth.

Grapes and red wines contain antioxidative phenolic compounds and organic acids that have antimicrobial properties. Previous research at the University of Missouri revealed that red wines had bactericidal effects against H. pylori, L. monocytogenes, E. coli O157:H7, S. typhimurium and S. boydii, based on agar diffusion and tube dilution tests.

The specific objectives of this research were to confirm bactericidal activity using the pour plate technique, and to investigate the effects of red wine and grape juice polyphenols against these pathogens and the probiotics L. acidophilus, L. paracasei, L. rhamnosus and B. longum.

It appears that the pathogens tested were killed by the red wines and grape juice, while the probiotics were more resistant to the beverages. The drier the red wine, the greater the inhibitory impact, while the opposite was observed with the sweeter red wines. Furthermore, red grape juice was more inhibitory than white grape juice against the pathogens and probiotics.

Researchers screened commercially available red wines and grape juices at 40% to 100% against the pathogens. Upon a 24-hour exposure to the 40% red wines, the numbers of each pathogen decreased from [10.sup.8] to [10.sup.9] CFU per mL to [10.sup.4] to [10.sup.5] CFU per mL. Barton Merlot, Pinot Noir and Shiraz caused a 5-log reduction of all of the pathogens, compared to a 3-log reduction by Zinfandel and cherry wine.

L. paracasei was the most sensitive probiotic tested against Kenwood and Chambourcin, undergoing a 4-log reduction in numbers. L. acidophilus was the most resistant against Shiraz and Kenwood, experiencing only a 1-log reduction. All of the pathogens were inhibited by the 50% to 60% red and by the 60% white grape juices. This indicated that the alcohol present in wines is not the only factor involved in their bactericidal effect. Red and white grape juices maintained a 3-log and 1-log reduction, respectively, of the probiotics tested. L. rhamnosus was the most sensitive to the red grape juices tested among the four probiotics. A certain commercial brand of red grape juice was more inhibitory toward all four probiotics than other red and white grape juice brands.

Further information. Azlin Mustapha, Food Science, University of Missouri-Columbia, 256 William Stringer Wing, Eckles Hall, Columbia, MO 65211; phone: 573-882-2649; fax: 573-882-0596; email: mustaphaa@missouri.edu.

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