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

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

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