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Qixin Zhong - One of the best experts on this subject based on the ideXlab platform.
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antibacterial activity of acidified sodium benzoate against escherichia coli o157 h7 salmonella enterica and listeria monocytogenes in Tryptic Soy Broth and on cherry tomatoes
International Journal of Food Microbiology, 2018Co-Authors: Huaiqiong Chen, Qixin ZhongAbstract:Abstract Concerns about undesirable by-products from chlorine sanitation of fresh produce and the limited efficacy with the presence of organic matter, have led to studies on alternative washing solutions. The aim of this study was to evaluate the antibacterial activities of acidified sodium benzoate (NaB) solutions against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes in growth medium and on cherry tomatoes. Experimentally, the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs, >3 Log reduction) of NaB against E. coli O157:H7 ATCC 43895, S. Enteritidis, and L. monocytogenes Scott A were determined at pH 7.0–4.0 using micro-Broth dilution method and agar plating method, respectively. The reduction of the three bacteria in Tryptic Soy Broth (TSB) by 500 and 1000 ppm NaB at pH 2.0, 2.5 and 3.0 for 30 min at 21 °C was compared. Residual bacterial cocktails inoculated on cherry tomatoes were determined after soaking in 3000 ppm NaB solution adjusted to pH 2.0 for 3 min at 21 °C. Results showed that the MBC of NaB reduced from >10,000 ppm at pH 7.0 to 1000 ppm at pH 4.0 and was identical for the three bacteria. The log reduction of bacteria in TSB indicated that 1000 ppm NaB at pH 2.0 was the most effective in killing the three pathogens. The respective reduction of E. coli O157:H7 and S. enterica cocktails inoculated on cherry tomatoes immersed in 3000 ppm NaB (pH 2.0) at 21 °C for 3 min was 4.99 ± 0.57 and 4.08 ± 0.65 log CFU/g, which was significantly higher (p 0.05) to 200 ppm chlorine. Furthermore, the reduction of bacterial cocktails on tomatoes by 3000 ppm NaB at pH 2.0 was not affected after adding 1% tomato puree, and bacteria were not detected in NaB washing solutions with and without 1% tomato puree and on following un-inoculated tomatoes. This study showed that acidified NaB solution may be used as an alternative post-harvest wash of produce.
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Lactobionic acid enhances the synergistic effect of nisin and thymol against Listeria monocytogenes Scott A in Tryptic Soy Broth and milk.
International Journal of Food Microbiology, 2017Co-Authors: Huaiqiong Chen, Qixin ZhongAbstract:Abstract Listeria monocytogenes is a Gram-positive opportunistic human pathogen and it remains a significant cause of foodborne illnesses. A variety of natural and synthetic compounds have been studied to inhibit the growth of L. monocytogenes in foods. Antimicrobial combinations with synergistic antilisterial properties can reduce the dose of each antimicrobial, which can be further enhanced by chelating compounds. Therefore, the objective of this study was to determine antilisterial properties of binary or ternary combinations of lactobionic acid (LBA), nisin, and thymol in Tryptic Soy Broth (TSB), 2% reduced-fat milk, and whole milk. The results showed that the minimum inhibitory concentration (MIC) of nisin, thymol and LBA was 125 IU/mL, 0.25 mg/mL, and 10 mg/mL, respectively. The ternary combination was the most effective in reducing MICs of antimicrobials, with the MIC of nisin, thymol, and LBA being 31.25 IU/mL, 0.0625 mg/mL, and 1.25 mg/mL, respectively. In TSB with 0.6% yeast extract, L. monocytogenes grew in individual or binary antimicrobial treatments of 31.25 IU/mL nisin, 0.0625 mg/mL thymol, and 1.25 mg/mL LBA within 24 h at 32 °C, while it was completely inhibited by the ternary combination. In 2% reduced-fat milk at 21 °C, the ternary combination of nisin, thymol, and LBA at respective concentrations of 250 IU/mL, 2 mg/mL, and 10 mg/mL completely inhibited the bacterium to below the detection limit in 72 h while > 2 log (CFU/mL) bacteria was still detected in all the binary combinations after 120 h. In whole milk, the combination of 500 IU/mL nisin, 2 mg/mL thymol, and 10 mg/mL LBA reduced bacteria to around 2 log (CFU/mL) in 4 h at 21 °C, and no bacterial recovery was observed after 5 d. This study suggested the potential of the ternary combination of nisin, thymol and LBA for food preservation.
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Antimicrobial activity of nanodispersed thymol in Tryptic Soy Broth.
Journal of Food Protection, 2013Co-Authors: Bhavini Shah, P. Michael Davidson, Qixin ZhongAbstract:Food safety is a continuing challenge for the food industry due to sporadic illness outbreaks caused by foodborne pathogens. Plant essential oils have been studied extensively as natural antimicrobials to control foodborne pathogens. However, their hydrophobic nature makes application in foods difficult because of their low water solubility, adverse impact on sensory quality, and binding with food components, which can interfere with antimicrobial efficacy. The objective of this study was to characterize antimicrobial activities of transparent nanodispersions of thymol encapsulated in whey protein isolate-maltodextrin conjugates, with comparison to free thymol. Tests were conducted for Escherichia coli O157:H7 strains ATCC 43889 and 43894, Salmonella Typhimurium strain 2576, Listeria monocytogenes strains Scott A and 101, and Staphylococcus aureus strains 27708 and SA113 in Tryptic Soy Broth at various pHs and temperatures. Results indicate that the MIC for nanodispersed and free thymol against all strains of both gram-negative and gram-positive pathogens tested was 500 ppm at pH 6.8 and at the optimal growth temperature, with the exception of E. coli O157:H7 and L. monocytogenes strain Scott A, which were inhibited by 300 ppm of free thymol. Nanodispersed thymol was further tested at 500 ppm for inhibition of E. coli O157:H7 and L. monocytogenes at 35, 32, 25, and 4°C in Tryptic Soy Broth adjusted to pH 5.5 and 3.5. At pH 5.5, L. monocytogenes was completely inhibited after 3 h, and E. coli O157:H7 showed a reduction of 1.0 to 3.0 log CFU/ml after 48 h. At pH 3.5, L. monocytogenes controls did not grow, but E. coli O157:H7 survived. At both pH 5.5 and 3.5, no significant effect of temperature on antimicrobial activity was observed at 500 mg/ml nanodispersed thymol. The present study demonstrated that transparent nanodispersions of thymol have promising antimicrobial activity against a broad spectrum of foodborne pathogens.
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Antimicrobial properties of lauric arginate alone or in combination with essential oils in Tryptic Soy Broth and 2% reduced fat milk.
International Journal of Food Microbiology, 2013Co-Authors: P. Michael Davidson, Qixin ZhongAbstract:Abstract The objective of this study was to evaluate the antimicrobial activity of lauric arginate (LAE) when used alone or in combination with the essential oil (EO) from cinnamon leaf and EO components, thymol and eugenol. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) for Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella Enteritidis were determined by the microBroth dilution method in Tryptic Soy Broth (TSB) at their optimal growth temperatures. The MIC for LAE was 11.8 ppm against L. monocytogenes and E. coli O157:H7 and 23.5 ppm against S. Enteritidis. Synergistic antimicrobial activity was demonstrated against L. monocytogenes with combinations of LAE and cinnamon leaf oil or eugenol, while the LAE and thymol combination showed additive antimicrobial activity. Conversely, antagonistic effects were shown for all combinations against E. coli O157:H7 and S. Enteritidis. Beef extract, at 2 or 5% w/v in TSB, showed no effects on the MIC and MBC of LAE against L. monocytogenes, while soluble starch from potato, at 2–10% w/v in TSB, increased the MIC and MBC. When tested in 2% reduced fat milk, significantly higher levels of antimicrobials were required to achieve similar inhibitions as in TSB. The growth curves of bacteria at 21 °C followed similar trends as in TSB, showing synergism against the Gram-positive L. monocytogenes and antagonism against the two Gram-negative bacteria. Findings suggest that application of LAE could enhance microbial food safety, especially when used in combination with EO to inhibit the growth of Gram-positive bacteria.
Barakat S.m. Mahmoud - One of the best experts on this subject based on the ideXlab platform.
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inactivation effect of x ray treatments on cronobacter species enterobacter sakazakii in Tryptic Soy Broth skim milk low fat milk and whole fat milk
Letters in Applied Microbiology, 2009Co-Authors: Barakat S.m. MahmoudAbstract:Aims: To determine the inactivation effect of X-ray treatments on Cronobacter (E. sakazakii) in Tryptic Soy Broth (TSB), skim milk (0% fat), low-fat milk (1% and 2%) and whole-fat milk (3AE5%). Methods and Results: X-rays were produced using the RS 2400 generator system (Rad Source Technologies Inc.). Cronobacter (in TSB), inoculated skim milk (0% fat), low-fat milk (1% and 2% fat) and whole-fat milk (3AE5% fat) were treated with 0AE0, 0AE1, 0AE5, 0AE75, 1AE0, 2AE0, 3AE0, 4AE0, 5AE0 and 6AE0 kGy X-ray doses. Surviving bacteria in the TSB and inoculated milk, before and after treatment, were enumerated using plating method onto Trypticase Soy agar. Greater than 7AE0-log CFU reduction in Cronobacter population was observed with 4AE0, 5AE0, 6AE0, 6AE0 and 6AE0 kGy X-ray in the TSB, skim milk, 1% fat milk, 2% fat milk and 3AE5% fat milk, respectively. Conclusions: Treatment with X-rays significantly (P <0 AE05) reduced Cronobacter to less than detectable limits (<1 log CFU ml )1 ) in skim milk at 5AE0 kGy and milk with 1% fat content and greater at 6AE0 kGy dose levels. The D-value for Cronobacter in TSB was significantly (P <0 AE05) lower than those in milk samples. Significance and Impact of the Study: Treatment with X-rays could be an effective and safe alternative technology to control pathogenic bacteria (Cronobacter) in the dairy industry.
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Inactivation effect of X‐ray treatments on Cronobacter species (Enterobacter sakazakii) in Tryptic Soy Broth, skim milk, low‐fat milk and whole‐fat milk*
Letters in Applied Microbiology, 2009Co-Authors: Barakat S.m. MahmoudAbstract:Aims: To determine the inactivation effect of X-ray treatments on Cronobacter (E. sakazakii) in Tryptic Soy Broth (TSB), skim milk (0% fat), low-fat milk (1% and 2%) and whole-fat milk (3AE5%). Methods and Results: X-rays were produced using the RS 2400 generator system (Rad Source Technologies Inc.). Cronobacter (in TSB), inoculated skim milk (0% fat), low-fat milk (1% and 2% fat) and whole-fat milk (3AE5% fat) were treated with 0AE0, 0AE1, 0AE5, 0AE75, 1AE0, 2AE0, 3AE0, 4AE0, 5AE0 and 6AE0 kGy X-ray doses. Surviving bacteria in the TSB and inoculated milk, before and after treatment, were enumerated using plating method onto Trypticase Soy agar. Greater than 7AE0-log CFU reduction in Cronobacter population was observed with 4AE0, 5AE0, 6AE0, 6AE0 and 6AE0 kGy X-ray in the TSB, skim milk, 1% fat milk, 2% fat milk and 3AE5% fat milk, respectively. Conclusions: Treatment with X-rays significantly (P
Changsu Park - One of the best experts on this subject based on the ideXlab platform.
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effect of Tryptic Soy Broth tsb and luria bertani lb medium on production of subtilisin cp 1 from bacillus sp cp 1 and characterization of subtilisin cp 1
Journal of Life Science, 2012Co-Authors: Changsu ParkAbstract:A bacterial strain producing a fibrinolytic enzyme, subtilisin CP-1, was isolated from Doen-Jang, a Korean traditional fermentation food. Based on the analysis of gene sequence of 16S rRNA and biochemical analysis, the strain was identified as Bacillus sp. and named as Bacillus sp. CP-1. To investigate the effect of the medium on the production of fibrinolytic enzyme from Bacillus sp. CP-1, two commercial bacterial culture media, Tryptic Soy Broth (TSB) and Luria-Bertani (LB), were applied to the cultivation of Bacillus sp. CP-1. The strain secreted only one proteolytic enzyme (subtilisin CP-1) in the culture Broth. The molecular weight of subtilisin CP-1 was estimated to be 28 kDa. Subtilisin CP-1 was optimally active at pH 9.0 and , and exhibited high specificity for Meo-Suc-Arg-Pro-Tyr-pNA (S-2586), a synthetic chromogenic substrate for chymotrypsin. The first eight amino acid residues of the N-terminal sequence of the enzyme are AQSVPYGI; this sequence is identical to that of subtilisin NAT and E.
Alley E. Watada - One of the best experts on this subject based on the ideXlab platform.
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Freeze-dried spinach powder inhibits growth of Listeria species and strains in Tryptic Soy Broth
HortScience, 1998Co-Authors: Isabelle Babic, Alley E. WatadaAbstract:A study was undertaken to determine the inhibitory effect of freeze-dried spinach (Spinacia oleracea L.) powder and its native mesophilic aerobic microorganisms (MAM) on the growth of six strains, representing three species, of Listeria in Tryptic Soy Broth (TSB). The cultures were incubated at 10°C and growth was measured daily. Both spinach powder and MAM inhibited growth; maximum populations at 6 days were 8.8 Log 10 colony-forming units (cfu) per mL -1 in control, 6.4 in spinach powder cultures, and 7.4 in MAM cultures. These results indicated that growth of various Listeria species/strains was affected by the bacteriostatic effect of spinach powder and competitive effect of native microorganisms.
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Growth of Listeria monocytogenes Restricted by Native Microorganisms and Other Properties of Fresh-Cut Spinach †.
Journal of Food Protection, 1997Co-Authors: Isabelle Babic, Alley E. Watada, J. G. ButaAbstract:A study was undertaken to investigate the cause of the bacteriostatic activity of fresh-cut spinach leaves against Listeria monocytogenes. L. monocytogenes was cultivated in pure Tryptic Soy Broth for use as a monoculture, in Tryptic Soy Broth containing 10 mg ml−1 of autoclaved or nonautoclaved freeze-dried spinach powder, and in Tryptic Soy Broth in mixed cultures with various microorganisms isolated from fresh-cut spinach, including Pseudomonas fluorescens biovar I, P. fluorescens biovar III, Staphylococcus xylosus, and an undefined culture of mesophilic aerobic microorganisms (MAMs) isolated from freeze-dried spinach powder. These microorganisms were inoculated at 4.4 log CFU ml−1 and L. monocytogenes was inoculated at 2.4 and 4.4 log CFU ml−1 After 24 h of incubation at 30°C, the populations of the two inoculum levels L. monocytogenes increased to 9.0 and 9.6 log CFU ml−1 in the Tryptic Soy Broth control, to 5.4 and 7.5 in nonautoclaved spinach powder cultures, and to 8.8 and 9.1 log CFU ml−1 in auto...
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Inhibitory Effect of Fresh-cut Spinach on Listeria monocytogenes
HortScience, 1995Co-Authors: Isabelle Babic, Alley E. WatadaAbstract:Studies. were undertaken to investigate the cause of the bacteriostatic activity of spinach leaves against Listeria monocytogenes. Listeria monocytogenes was inoculated at the concentration 104 cells/ml in raw, autoclaved and vacuum filtration sterilized spinach macerates as well as in Tryptic Soy Broth used as control. The concentrations after 24 h at 28C were 105, 5 × l06 and 105 cells/ml in respective spinach macerates and 4 × l08 cells/ml in Tryptic Soy Broth. The anti-Listeria activity was still present in spinach macerates sterilized by vacuum filtration but strongly reduced in autoclaved macerates. Serial dilutions of freeze-dried spinach were tested on the growth of Listeria monocytogenes in Tryptic Soy Broth. The minimum concentration for maximum inhibition was 10 mg·ml–1. The growth of Listeria monocytogenes in Tryptic Soy Broth in mixed cultures with different microbial species isolated from spinach was not inhibited. In conclusion, the bacteriostatic activity against Listeria monocytogenes might be due to antimicrobial compounds present in spinach leaves.
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SURVIVAL OF LISTERIA MONOCYTOGENES ON LIGHTLY PROCESSED SPINACH
HortScience, 1995Co-Authors: Isabelle Babic, Alley E. WatadaAbstract:The population of Listeria monocytogenes inoculated on lightly processed spinach held at 5C or 10C remained constant for 9 days, whereas the populations of mesophilic aerobic flora, pseudomonas, and enterobacteria increased sharply. We studied the cause of the bacteriostatic activity of spinach leaves against L. monocytogenes. Listeria monocytogenes were inoculated at the concentration of 2 × 104 cells/ml in raw, autoclaved and vacuum filtration sterilized spinach macerates as well as in Tryptic Soy Broth used as control. The concentrations after 24 hat 28C were 2 × 104, 4 × 107, and 4 × 105 cells/ml in respective spinach macerates and 4 × 108 cells/ml in Tryptic Soy Broth. The anti-listeria activity was still present in spinach macerates sterilized by vacuum filtration but not in autoclaved macerates. In conclusion, the bacteriostatic activity against L. monocytogenes might be due to antimicrobial compounds present in spinach leaves or produced by the other microorganisms. Studies are being continued to identify the compounds involved in the anti-listeria activity.
Huaiqiong Chen - One of the best experts on this subject based on the ideXlab platform.
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antibacterial activity of acidified sodium benzoate against escherichia coli o157 h7 salmonella enterica and listeria monocytogenes in Tryptic Soy Broth and on cherry tomatoes
International Journal of Food Microbiology, 2018Co-Authors: Huaiqiong Chen, Qixin ZhongAbstract:Abstract Concerns about undesirable by-products from chlorine sanitation of fresh produce and the limited efficacy with the presence of organic matter, have led to studies on alternative washing solutions. The aim of this study was to evaluate the antibacterial activities of acidified sodium benzoate (NaB) solutions against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes in growth medium and on cherry tomatoes. Experimentally, the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs, >3 Log reduction) of NaB against E. coli O157:H7 ATCC 43895, S. Enteritidis, and L. monocytogenes Scott A were determined at pH 7.0–4.0 using micro-Broth dilution method and agar plating method, respectively. The reduction of the three bacteria in Tryptic Soy Broth (TSB) by 500 and 1000 ppm NaB at pH 2.0, 2.5 and 3.0 for 30 min at 21 °C was compared. Residual bacterial cocktails inoculated on cherry tomatoes were determined after soaking in 3000 ppm NaB solution adjusted to pH 2.0 for 3 min at 21 °C. Results showed that the MBC of NaB reduced from >10,000 ppm at pH 7.0 to 1000 ppm at pH 4.0 and was identical for the three bacteria. The log reduction of bacteria in TSB indicated that 1000 ppm NaB at pH 2.0 was the most effective in killing the three pathogens. The respective reduction of E. coli O157:H7 and S. enterica cocktails inoculated on cherry tomatoes immersed in 3000 ppm NaB (pH 2.0) at 21 °C for 3 min was 4.99 ± 0.57 and 4.08 ± 0.65 log CFU/g, which was significantly higher (p 0.05) to 200 ppm chlorine. Furthermore, the reduction of bacterial cocktails on tomatoes by 3000 ppm NaB at pH 2.0 was not affected after adding 1% tomato puree, and bacteria were not detected in NaB washing solutions with and without 1% tomato puree and on following un-inoculated tomatoes. This study showed that acidified NaB solution may be used as an alternative post-harvest wash of produce.
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Lactobionic acid enhances the synergistic effect of nisin and thymol against Listeria monocytogenes Scott A in Tryptic Soy Broth and milk.
International Journal of Food Microbiology, 2017Co-Authors: Huaiqiong Chen, Qixin ZhongAbstract:Abstract Listeria monocytogenes is a Gram-positive opportunistic human pathogen and it remains a significant cause of foodborne illnesses. A variety of natural and synthetic compounds have been studied to inhibit the growth of L. monocytogenes in foods. Antimicrobial combinations with synergistic antilisterial properties can reduce the dose of each antimicrobial, which can be further enhanced by chelating compounds. Therefore, the objective of this study was to determine antilisterial properties of binary or ternary combinations of lactobionic acid (LBA), nisin, and thymol in Tryptic Soy Broth (TSB), 2% reduced-fat milk, and whole milk. The results showed that the minimum inhibitory concentration (MIC) of nisin, thymol and LBA was 125 IU/mL, 0.25 mg/mL, and 10 mg/mL, respectively. The ternary combination was the most effective in reducing MICs of antimicrobials, with the MIC of nisin, thymol, and LBA being 31.25 IU/mL, 0.0625 mg/mL, and 1.25 mg/mL, respectively. In TSB with 0.6% yeast extract, L. monocytogenes grew in individual or binary antimicrobial treatments of 31.25 IU/mL nisin, 0.0625 mg/mL thymol, and 1.25 mg/mL LBA within 24 h at 32 °C, while it was completely inhibited by the ternary combination. In 2% reduced-fat milk at 21 °C, the ternary combination of nisin, thymol, and LBA at respective concentrations of 250 IU/mL, 2 mg/mL, and 10 mg/mL completely inhibited the bacterium to below the detection limit in 72 h while > 2 log (CFU/mL) bacteria was still detected in all the binary combinations after 120 h. In whole milk, the combination of 500 IU/mL nisin, 2 mg/mL thymol, and 10 mg/mL LBA reduced bacteria to around 2 log (CFU/mL) in 4 h at 21 °C, and no bacterial recovery was observed after 5 d. This study suggested the potential of the ternary combination of nisin, thymol and LBA for food preservation.
