Antimicrobial effect of water-soluble arrowroot (Puerariae radix) tea extract on foodborne pathogens and development of innovative microbiological methods.

摘要

The microbial inhibition of Escherichia coli O157:H7, Salmonella Enteritidis, Listeria monocytogenes, and Staphylococcus aureus was determined in Brain Heart Infusion (BHI) broth with 10% (v/v) water-soluble tea extracts. Jasmine and green tea extracts inhibited L. monocytogenes and S. aureus in BHI broth. In ground beef, there was no antimicrobial effect of all the tea extracts at 0.1%. The antimicrobial effect of arrowroot tea extract was evaluated at 0, 0.63, 1.25, 2.5, and 5.0% (w/v) in BHI. At 5%, it suppressed E. coli O157:H7, S. Enteritidis, L. monocytogenes, and S. aureus by 6--7 log CFU/ml compared to the control. In ground beef with 3% and 6% arrowroot tea, S. Enteritidis and L. monocytogenes were suppressed by about 1.5 log CFU/ml compared to the control. In mushroom soup, 1% arrowroot tea extract showed 2.3 log and 2.7 log suppression of S. Enteritidis and S. aureus, respectively, compared to the control. Also there were 6.5, 4.7, 3.4, and 4.3 log reduction at 5%; 6.0, 4.7, 5.0, and 4.3 log reduction at 10%, of E. coli O157:H7, S. Enteritidis, L. monocytogenes, and S. aureus, respectively, compared to the control. Transmission Electron Microscopy (TEM) images showed that all the strains treated with 5% arrowroot tea extract were injured or killed by the rupture of cell membranes and non-homogeneous disposition of cytoplasmic materials in a cell.; Kang-Fung-Sol (KFS) agar was designed to selectively grow lactic acid bacteria (LAB) from mixed culture by incorporating 0.2% lactic acid into Kang-Fung (KY) medium. deMan Rogosa Sharpe (MRS), KF, and KFS agar were evaluated on selective growth of LAB. KFS completely inhibited the growth of all non-LAB with the same recovery of LAB as MRS and KF. Therefore, KFS can be used to isolate and enumerate LAB in a mixed culture or ground beef in the presence of other microorganisms.; A modified Microtiter count method was compared with a Spiral-plating method in viable cell counts of 3 bacteria and natural microflora from meat products. There was excellent correlation between the two methods: E. coli O157:H7, r = 0.984; S. Enteritidis, r = 0.995; L. monocytogenes, r = 0.994; and natural microflora, r = 0.897.