Antimicrobial activity of water-soluble arrowroot tea extract was evaluated against Escherichia coli O157:H7, Salmonella enterica Serotype Enteritidis, Listeria monocytogenes, and Staphylococcus aureus in ground beef and mushroom soup. The concentrations of arrowroot tea used were 0, 3, and 6% (wt/wt) for ground beef and 0, 1, 5, and 10% (wt/vol) for mushroom soup. Samples without tea extract were considered controls. Each sample was stored for 0, 1, 3, 5, and 7 days at 7°C for ground beef and for 0, 1, 3, and 5 days at 35°C for mushroom soup. On each sampling time, proper dilutions were spread plated on each pathogen-specific agar. Viable cell counts of each pathogen were performed after incubation at 35°C for 24 to 48 h. For ground beef, Salmonella Enteritidis and L. monocytogenes were slightly suppressed by approximately 1.5 log, compared with the control, on day 7 at 3 and 6% arrowroot tea treatment. For mushroom soup, all test pathogens were suppressed by 6.5, 4.7, 3.4, and 4.3 log at 5% and 6.0, 4.7, 5.0, and 4.3 log at 10% against E. coli O157:H7, Salmonella Enteritidis, L. monocytogenes, and S. aureus, respectively, compared with the control on day 5. Mushroom soup with 1% arrowroot tea also showed 2.3- and 2.7-log growth suppression of Salmonella Enteritidis and S. aureus, respectively, compared with the control on day 5. This study showed that the use of arrowroot tea would effectively inhibit the microbial growth of both gram-negative and gram-positive foodborne pathogens in various foods, especially liquid foods.

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