Mechanism of inhibitory action of potassium sorbate in Escherichia coli

Subbacteriostatic, growth-inhibitory concentrations of potassium sorbate (125, 250, and 500 [mu]g/ml) at pH 5.70 increased the rate of proton translocation, and strongly inhibited the transport of arginine, glutamic acid, phosphate, and sulfate by whole cells of E. coli K12. Potassium sorbate (125 [mu]g/ml) had almost no effect on the uptake of glucose, thymine, or uracil by E. coli 15TAU or E. coli K12 but effectively inhibited the synthesis of DNA, RNA, and protein in both organisms. All three concentrations of sorbate inhibited respiration (oxygen consumption) in E. coli K12 but failed to induce leakage of [superscript]14C-labeled intracellular materials from radiolabeled cells of that same organism. There was a relatively small difference (8%) in the inhibition of glutamate and arginine uptake in whole cells of E. coli K12 by potassium sorbate (125 [mu]g/ml);The results of the present study suggest that potassium sorbate increases the permeability of E. coli cells to protons and probably other small ions thus decreasing the proton gradient as well as the charge difference across the cytoplasmic membrane. This action can diminish the capacity of the cytoplasmic membrane to function in the active transport of nutrients such as amino acids, and inorganic ions essential to the growth of the bacterial cell

Clickers and HACCP: Educating a Diverse Food Industry Audience with Technology

Hazard Analysis Critical Control Points (HACCP) is a systematic approach to food safety education for the food industry. To receive a HACCP certificate, participants must receive an 80% or higher on the final examination. Language barriers, educational levels, and age have been noted as primary reasoning\u27s for not passing the final examination. Clicker technology has been shown to improve knowledge transfer to students in various classroom settings. Incorporation of mock final examination questions using Clickers into a traditional HACCP course has been shown in a small pilot study to increase the pass rate

Evaluation of Reverse Transcriptase 5\u27 Nuclease Polymerase Chain Reaction assay for the Detection of Viable Heat-Injured and Resuscitated Listeria monocytogenes in Ground Pork

An anaerobic resuscitation-enrichment system was combined with a 5\u27 nuclease reverse transcriptase (RT) protocol for detecting Listeria monocytogenes Scott A from artificially inoculated ground pork. When irradiation-sterilized ground pork containing L. monocytogenes (~6 x 10 5 CFU/g) was heated (60 o C, 14 min), 100% of the cells were injured, as indicated by no growth on selective Modified Oxford (MOX) agar plates incubated aerobically. After resuscitation and enrichment (37°C) in anaerobic Penn State University (PSU) broth, L. monocytogenes was detected within 24 hours both by plating to MOX agar incubated in air and by a fluorogenic 5\u27 nuclease real-time RT-PCR assay. The RT-5\u27 nuclease polymerase chain reaction (PCR) assay targeting the hemolysin gene (hlyA) detected viable L. monocytogenes directly from the PSU within 24 hours, although a stronger signal was detected after 48 hours of resucitation. The RT-5\u27 nuclease PCR assay bypassed the need for subsequent plating of ground pork to selective agar and thus may shorten the interval to detect low numbers of viable L. monocytogenes following heating of naturally contaminated meat

Influence of Zn2 + , Sodium Bicarbonate, and Citric Acid on the Antibacterial Activity of Ovotransferrin against E. coli O157:H7 and L. monocytogenes in Model Systems and Ham

The antibacterial activity of natural apo-ovotransferrin against E. coli O157:H7 and L. monocytogenes in model systems increased as the concentration of sodium bicarbonate increased. NaHCO3 at 100 mM markedly increased antibacterial activity of ovotransferrin against E. coli O157:H7 and L. monocytogenes. Citric acid at 0.5% enhanced antibacterial activity of apo-ovotransferrin against E. coli O157:H7, but 0.5% citric acid alone also showed a strong bactericidal activity against L. monocytogenes. Addition of NaHCO3 negated the strong antibacterial activity of ovotransferrin plus citric acid against the two pathogens. The antimicrobial activity of ovotransferrin was greatly enhanced by acidic pH conditions. Zn-bound ovotransferrin produced a bacteriostatic effect against L. monocytogenes, but Fe-bound ovotransferrin had little or no antibacterial activity against E. coli O157:H7 and L. monocytogenes. Considering these results, iron bind capacity of ovotransferrin is not the major cause of antibacterial action of ovotransferrin. Previous studies indicate that ovotransferrin directly interacts with bacterial membranes causing a variety of physiochemical changes which affect the survival of microorganisms. Ovotransferrin plus 100 mM NaHCO3 did not exhibit any antibacterial activity against two pathogens in commercial hams, whereas ovotransferrin + 0.5% citric acid suppressed L. monocytogenes in irradiated hams but not in non-irradiated hams. There are some limitations of using ovotransferrin to control pathogens in meat or meat products. To overcome these problems, further studies are needed to determine the mechanisms of antibacterial activity of ovotransferrin and to identify various factors that can improve the antibacterial activity of ovotransferrin

Effect of EDTA and Lysozyme on the Antimicrobial Activity of Ovotransferrin against Listeria monocytogenes

This study evaluated the effect of EDTA and lysozyme on the antibacterial activities of activated ovotransferrin against 5 strains of L. monocytogenes. First, a disc test was performed to screen the concentrations of EDTA or lysozyme that showed antibacterial activities in ovotransferrin (O) or ovotransferrin in 100 mM NaHCO3 (OS) solution. Turbidity and viability test were conducted using O or OS solution combined with either lysozyme (OL and OSL) or EDTA (OE and OSE). Also, OS combined with 2 mg/ml lysozyme (OSL) or/and 1 mg/ml EDTA (OSLE) were applied on commercial hams to determine if the solutions show antibacterial activities on meat products. The effect of initial cell population on the antibacterial activities of ovotransferrin combined with either EDTA or lysozyme was also determined. L. monocytogenes started to grow after 1 day of incubation in the presence of \u3e 2.0 mg/ml lysozyme. OL groups showed weak antibacterial activities against L. monocytogenes in BHI broth culture and their activities were bacteriostatic. OSL groups were bactericidal against L. monocytogenes, resulting in 1 log reduction from initial cell population. Even though OSL showed stronger antibacterial activity than OS, lysozyme had no significant effect on antibacterial activity of OS against L. monocytogenes. Also, EDTA itself at 1.0 and 2.0 mg/ml were bacteriostatic against 5 strains of L. monocytogenes. They were more susceptible to EDTA than lysozyme, and OSE1 and OSE2 had bactericidal activity against L. monocytogenes. There was a significant difference in the survivor cell populations between OS and OSE groups (p \u3c 0.05). Therefore, EDTA enhanced the antibacterial activity of OS against L. monocytogenes. However, ovotransferrin plus either lysozyme or/and EDTA did not show any antibacterial effect in commercial hams during storage at 10 o C. In addition, the initial population of L. monocytogenes cells influenced the antibacterial activity of OSL or OSE

Clickers and HACCP: Educating a Diverse Food Industry Audience with Technology

Hazard Analysis Critical Control Points (HACCP) is a systematic approach to food safety education for the food industry. To receive a HACCP certificate, participants must receive an 80% or higher on the final examination. Language barriers, educational levels, and age have been noted as primary reasoning\u27s for not passing the final examination. Clicker technology has been shown to improve knowledge transfer to students in various classroom settings. Incorporation of mock final examination questions using Clickers into a traditional HACCP course has been shown in a small pilot study to increase the pass rate

EDTA and Lysozyme Improves Antimicrobial Activities of Ovotransferrin against Escherichia coli O157:H7

The aim of this study was to evaluate the effect of ethylenediaminetetraacetic acid (EDTA) or/and lysozyme on the antibacterial activity of ovotransferrin against E. coli O157:H7. Ovotransferrin solution (20 mg/ml) containing 100 mM-NaHCO3 (OS) was added with EDTA (2.0 or 2.5 mg/ml), lysozyme (1.0, 1.5, or 2.0 mg/ml) or both were prepared. Antibacterial activities of OS (20 mg/ml ovotransferrin + 100 mM-NaHCO3), OSE (OS+ EDTA), or OSL (OS + lysozyme) against E. coli O157:H7 in model systems were investigated by turbidity and viability tests. Also, OSE, OSL or OSEL (OS + EDTA + lysozyme) was applied on irradiated pork chops and commercial hams to determine if the solutions have antibacterial activity on meat products. The effect of initial cell population on the antibacterial activity of ovotransferrin and EDTA or lysozyme combinations was also determined. EDTA at 2 mg/ml plus OS (OSE2) induced 3 ~ 4 log reduction in viable E. coli O157:H7 cells in brain heart infusion (BHI) broth media, and 1 mg/ml lysozyme plus OS (OSL1) resulted in 0.5 ~ 1.0 log reduction during 35 oC incubation for 36 hr. However, OSE or OSEL did not show significant antibacterial effect on pork chops and hams during storage at 10 oC. The initial cell number in media did not affect the antibacterial activity of OSE or OSEL against E. coli O157:H7. This study demonstrates that combinations of ovotransferrin, NaHCO3, and EDTA (OSE) have potential to control E. coli O157:H7

Temperature Abuse Affects the Quality of Irradiated Pork Loins

Temperature abuse had no significant effect on color, oxidation, and volatiles of irradiated pork loins. However, temperature abuse improved water holding capacity of meat, which could be caused by the accelerated hydrolysis of muscle proteins at higher temperature. Irradiation increased redness, sulfur contents in volatiles and off-odor of pork loin. Off-odor and redness induced by irradiation sustained during storage. Among sulfur compounds, the content of dimethyl disulfide decreased gradually while the level of thiourea remained relatively constant. Irradiation also increased water loss, which might be related to the structural damage in membrane during irradiation. This study shows that temperature abuse has little effect on the quality of irradiated por

Fate of Listeria monocytogenes in Ready-to-Eat Turkey Breast Rolls Formulated with Antimicrobials Following E-Beam Irradiation

The objective of this study was to determine the effect of antimicrobials on the survival and proliferation of L. monocytogenes in turkey breast rolls following electronbeam irradiation. Six antimicrobial additive treatments that include no preservatives (control), 0.1% potassium benzoate (PB), 2% sodium lactate (SL), 0.1% potassium benzoate plus 2% sodium lactate (PB+SL), 2% sodium lactate plus 0.1% sodium diacetate (SL+SDA), and 0.1% potassum benzoate, 2% sodium lactate and 0.1% sodium diacetate (PB+SL+SDA) were used. Sliced turkey breast rolls were artificially inoculated with ~10 6 CFU/cm 2 five-strain- L. monocytogenes cocktails, then vacuum-packaged and irradiated at 0, 1.0, 1.5, 2.0 or 2.5 kGy. D10 values for breast rolls with various additive treatments ranged from 0.56 to 0.58 kGy. Adding PB (0.1%) or SL (2%) in turkey rolls failed to prevent L. monocytogenes from growing during refrigerated storage. In turkey rolls added with two (PB+SL or SL+SDA) or three (PB+SL+SDA) antimicrobial combinations had 2 or 3 weeks of lag phases before L. monocytogenes growth, respectively. Irradiating turkey rolls, which were added with PB+SL or SL+SDA, at 1.0 kGy was effective in suppressing the growth of L. monocytogenes for about six weeks when stored at 4 °C. No growth of L. monocytogenes after irradiation occurred during 42 d storage for 2.0 kGy irradiated breast rolls formulated with 0.1%PB+2%SL, 2%SL+0.1%SDA or 0.1%PB+2%SL+ 0.1%SDA, and 1.0 kGy irradiated turkey breast with 0.1% PB + 2% SL + 0.1% SDA. Sensory panelists found that low-dose irradiation (1.0 kGy) had no effect on the sensory characteristics of RTE turkey breast rolls. Including SL+SDA had slightly negative effect for nonirradiated turkey breast rolls, but the sensory characteristics of 1.0 kGy irradiated turkey roll containing SL+SDA was not significantly different from the others receiving 1.0kGy irradiation. For microbial safety, PB+SL and SL+ SDA antimicrobial treatments combined with 1.0 kGy or 2.0 kGy irradiation are a promising technology