Combination of Carbon Dioxide and Cinnamon to Inactivate Escherichia coli O157:H7 in Apple Juice

ABSTRACT: Pasteurized apple juice with CO2 (0, 1, and 4%) and cinnamon (0 and 0.3%) was inoculated with Escherichia coli O157:H7 at 104 CFU/mL, and stored at 5 and 20 °C. Counts on nonselective and selective media, and thin agar layer (TAL; selective medium overlaid with nonselective medium) were determined at 1 h and 1, 3, 7, and 14 d. Inactivation was greater at 20 °C. Samples with 1 and 4% CO₂, alone and combined with cinnamon, presented < 0.7 log CFU/mL in 3 d. Counts in apple juice inoculated at 10² CFU/mL, a low-level E. coli O157:H7 contamination, were nondetectable at 3 d. The TAL method was as effective as nonselective medium to recover injured cells.     

Decontamination Efficacy of Combined Chlorine Dioxide with Ultrasonication on Apples and Lettuce

ABSTRACT:  The bacterial reduction of Salmonella and Escherichia coli O157:H7-inoculated apples and lettuce by ClO₂ at 0, 5, 10, 20, and 40 ppm with and without 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, have been studied. The treatments of ClO₂ at 20 and 40 ppm for 3, 6, and 10 min or at 5 and 10 ppm for 6 and 10 min with 170-kHz ultrasonication caused 3.115 to 4.253 log reductions in Salmonella and 2.235 to 3.865 log reduction in E. coli O157:H7 on inoculated apples. Using combined ClO₂ and ultrasonication to treat 4.48 × 10⁴ CFU/g Salmonella and 1.07 × 10⁵ CFU/g E. coli O157:H7-inoculated lettuce, the bacterial reductions were 2.257 to 2.972 and 1.357 to 2.264 log, respectively. The residual ClO₂ decreased with increasing treatment times, over 80% of ClO₂ was detected after the 3-min treatment, and more than 70% remained after the 10-min treatment time. No bacteria were recovered from the posttreatment solutions of ClO₂ or ClO₂ combined with ultrasonication. The temperature of the ClO₂ treatment was 20.1 °C, and it increased to 40.1, 44.9, and 50.3 °C, with 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, on apples.     

Empirical Distribution Models for Escherichia coli 57:H7 in Ground Beef Produced by a Mid-size Commercial Grinder

ABSTRACT: The purpose of this research was to develop empirical models that describe the amount and distribution of ground beef contaminated with Escherichia coli O157:H7 when a contaminated beef trim is introduced into a batch of uncontaminated beef before processing in a mid-size commercial grinder (34 g/s). A beef trim was inoculated with a rifampacin-resistant strain of E. coli O157:H7 and added to a batch of noncontaminated trims at the grinding step. To study the distribution of the E. coli O157:H7^rif in the ground beef, 6 treatments with different inoculum levels (1 to 6 log₁₀ colony-forming units [CFU]) were tested. Removal or pick up of the residual contamination with E. coli O157:H7^rif left in the grinder was evaluated. E. coli O157:H7^rif was detected in 9% to 86% of the total ground beef for the 1 to 6 log₁₀ CFU inoculum levels, respectively. E. coli O157:H7^rif contamination was detected in the collar that fixes the grinder's die and blade to the hub. An exponential algorithm described the relationship between the quantities of ground beef containing E. coli O157:H7^rif and the inoculum level ( R ²= 0.82). Distribution models based on a Chi-squared algorithm were developed for each inoculum level describing the contamination level as a function of the batch fraction processed ( R ²= 0.81 to 0.99). The results of this study corroborate that when beef processors test for pathogenic contamination in a mid-scale grinder, they should test the beef residues in the collar that fixes the grinder's die and blade to the hub.     

Decontamination of Escherichia coli O157:H7 and Salmonella enterica on blueberries using ozone and pulsed UV-light

ABSTRACT:  Efficacy of gaseous ozone, aqueous ozone, and pulsed UV-light was evaluated for the purpose of decontaminating blueberries artificially contaminated with either Escherichia coli O157:H7 or Salmonella. Blueberries were exposed to 4 different gaseous ozone treatments: continuous ozone exposure, pressurized ozone exposure, and 2 combined treatments. Maximum reductions of Salmonella and E. coli O157:H7 after 64-min pressurized or 64-min continuous exposure were 3.0 and 2.2 log₁₀ CFU/g, respectively. Aqueous ozone experiments were conducted at 20 °C and 4 °C and zero plate counts were observed for E. coli O157:H7 and Salmonella after 64 min of ozone exposure at 20 °C. Finally, pulsed UV-light was evaluated at 3 different distances from the light. Maximum reductions of 4.3 and 2.9 log₁₀ CFU/g were observed at 8 cm from the light after 60 s of treatment for Salmonella and E. coli O157:H7, respectively. A sensory analysis as well as color analysis was performed on blueberries from each treatment agent; neither analysis detected a difference between treated and untreated blueberries. The results presented in this study indicate that ozone and pulsed UV-light are good candidates for decontamination of blueberries.     

Antimicrobial effect of electrolyzed oxidizing water against Escherichia coli O157:H7 and Listeria monocytogenes on fresh strawberries (Fragaria x ananassa)

ABSTRACT:  Antibacterial activity of electrolyzed oxidizing (EO) water prepared from 0.05% or 0.10% (w/v) sodium chloride (NaCl) solutions against indigenous bacteria associated with fresh strawberries ( Fragaria × ananassa ) was evaluated. The efficacy of EO water and sodium hypochlorite (NaOCl) solution in eliminating and controlling the growth of Listeria monocytogenes and Escherichia coli O157:H7 inoculated onto strawberries stored at 4 ± 1 °C up to 15 d was investigated at exposure time of 1, 5, or 10 min. Posttreatment neutralization of fruit surfaces was also determined. More than 2 log₁₀ CFU/g reductions of aerobic mesophiles were obtained in fruits washed for 10 or 15 min in EO water prepared from 0.10% (w/v) NaCl solution. Bactericidal activity of the disinfectants against L. monocytogenes and E. coli O157:H7 was not affected by posttreatment neutralization, and increasing exposure time did not significantly increase the antibacterial efficacy against both pathogens. While washing fruit surfaces with distilled water resulted in 1.90 and 1.27 log₁₀ CFU/mL of rinse fluid reduction of L. monocytogenes and E. coli O157:H7, respectively, ≥ 2.60 log₁₀ CFU/mL of rinse fluid reduction of L. monocytogenes and up to 2.35 and 3.12 log₁₀ CFU/mL of rinse fluid reduction of E. coli O157:H7 were observed on fruit surfaces washed with EO water and NaOCl solution, respectively. Listeria monocytogenes and E. coli O157:H7 populations decreased over storage regardless of prior treatment. However, EO water and aqueous NaOCl did not show higher antimicrobial potential than water treatment during refrigeration storage.     

Antimicrobial Efficiency of Essential Oil and Freeze–Thaw Treatments against Escherichia coli O157:H7 and Salmonella enterica Ser. Enteritidis in Strawberry Juice

ABSTRACT:  This study investigated the antimicrobial efficiency of 3 essential oils (EOs), lemongrass, cinnamon leaf, and basil, and freeze–thaw treatment, alone or in combination, against Escherichia coli O157:H7 and Salmonella enterica Ser. Enteritidis inoculated in strawberry juice stored at 7 °C. EO of lemongrass or cinnamon leaf at 0.1 to 2 μL/mL and freezing at −23 °C for 24 or 48 h followed by thawing at 7 °C for 4 h all showed significant antimicrobial activities ( P < 0.05) against E. coli O157:H7 and S. Enteritidis in strawberry juice. The antimicrobial activity increased with increasing EO concentration and storage time, but extending freezing time from 24 to 48 h did not enhance the antimicrobial activity of freeze–thaw treatment ( P > 0.05). EO of lemongrass or cinnamon leaf at 0.1 μL/mL and freeze–thaw treatment alone obtained a 5 log₁₀ reduction in the population of S. Enteritidis, while EOs at 0.1 to 0.3 μL/mL or freeze–thaw alone could not achieve a satisfactory protection against E. coli O157:H7 in strawberry juice. Combined EO and freeze–thaw treatment enhanced the overall antimicrobial effect against E. coli O157:H7, with adding EO before the freeze–thaw treatment showed a faster decontamination rate than when added EO after the freeze–thaw. EOs of lemongrass and cinnamon leaf at 0.1 or 0.3 μL/mL followed by the freeze–thawing resulted in a 5 log₁₀ reduction in E. coli O157:H7 on the 5th and 2nd day of storage, respectively. This study suggested that combined EO and freeze–thaw treatment may be a suitable and inexpensive method to eliminate microorganisms that can be a hazard for the consumers of unpasteurized berry juices.     

Reduction of Escherichia Coli O157:H7 and Lactobacillus Plantarum Numbers on Fresh Beef by Polylactic Acid and Vacuum Packaging

ABSTRACT: The efficacy of 2% molecular weight 240, 2% molecular weight 360 polylactic acid (PLA), and an equal mix of both at reducing numbers of Escherichia coli O157:H7 and Lactobacillus plantarum on raw beef was determined. Fresh beef cubes inoculated with either organism were dipped in PLA solutions or wrapped in PLA-sprayed films. Samples were vacuum packaged and stored at 4°C for 42 d. Treated samples maintained a significantly lower pH than controls. Growth of E. coli O157:H7 was totally inhibited by both PLA treatments by up to 7.29 log₁₀ CFU/cm² when the spray method was used. However, PLA treatments against L. plantarum were not very effective.     

LINKING MICROBIOLOGICAL CRITERIA FOR FOODS WITH QUANTITATIVE RISK ASSESSMENT

The current annual risk of acquiring a foodborne disease in the United States is estimated at 2.7 × 10^-2. The risk of associated death is estimated at 3.7 × 10^-5. These represent a health care burden >$3 billion. Using a risk assessment model one can identify levels of microbial contamination which may be unacceptable in foods and appropriate controls needed to reduce these levels. Salmonella bacteria continue to represent a large percentage of the identifiable infections. A model developed from human dose-response studies predicts the probability of infection for Salmonella at 7.5 × 10^-3 with exposure to a single CFU of the organism. Risks of severity (hospitalization), mortality, reactive arthritides, and mortality in the elderly are estimated at 3.1 × 10^-6, 7.5 × 10^-6, 1.7 × 10^-5, and 2.8 × 10^-4. Exposure to microbial contaminants needs to be evaluated on a single meal basis. For chicken, exposure may range from a single drum stick (38g) to a half broiler (176g) but averages around 80g. For beef between 51 and 85g may be consumed during a single meal. Therefore, methods for monitoring must be able to detect at least 1 CFU/80g. Risks for some pathogenic E. coli are estimated at 1,000 to 10,000 less than Salmonella. Therefore, use of coliforms as indicators needs to be assessed and related to occurrence and survival and regrowth potential of the enteric bacteria of greater public health concern. Because, 20% of the U.S. population may be considered to be in a special population category and at an increased risk of severe outcomes, no more than 20% failure of a standard should be acceptable .     

Validation of Dry Cured Ham Process for Control of Pathogens

ABSTRACT: The dry curing process for hams to control Salmonella spp., Escherichia coli O157:H7, Listeria monocytogenes , and Staphylococcus aureus was evaluated. Fresh hams, surface inoculated with each microorganism, were processed by a commercial style process. There was no significant (p < 0.05) difference in reduction of microbial populations between ham sampling locations (cushion, butt, hock). Interaction of salt concentration (8%), pH (5.5), ham storage temperature (20 °C), and ham aw (0.92) limited staphylococcal proliferation. Mean log reduction of Salmonella spp., E. coli O157:H7 and L. monocytogenes populations on inoculated hams after 69 d of curing were 5.5, 5.5, and 4.0 CFU/cm², respectively and after 120 d were 5.7, 5.5, and 4.8 CFU/cm², respectively. Keywords: dry cured ham, Salmonella, Esherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus     

CONCURRENT DETECTION OF ESCHERICHIA COLI O157:H7 AND SALMONELLA FROM A SINGLE ENRICHMENT IN 24 H

The objective of this study was to determine if a single assay protocol could result in the concurrent detection of Escherichia coli O157:H7 and Salmonella from a single sample grown in a single enrichment in 24 h. Twenty-five and 375 g of ground beef nonfat dry milk, and dry pet food samples were seeded with low (10 cfu/sample) and high (100 cfu/sample) levels ofE. coli O157:H7 and Salmonella cultures and incubated at 35 and 41C for 18 h for nonselective preenrichment. Incubated samples were analyzed by immunomagnetic separation (IMS) following a 6 h incubation for selective enrichment at 37C using M-broth and enzyme linked immumosorbent assay (ELISA). Depending on the food samples and the inoculation level, the minimum concurrent detection level of E. coli O157:H7 and Salmonella was <1 cfu/g in the samples at the competitor flora level of 10⁵ cfu/g or less in ground beef samples, but in other cases of higher competitor loads and low target inoculations E. coli O157:H7 could not be detected in the presence of the Salmonella.     

Comparative Study of Thermal Inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in Ground Pork

ABSTRACT: Thermal inactivation of Escherichia coli O157:H7, Salmonella , and Listeria monocytogenes in ground pork was compared. The D (decimal reduction time at a certain heating temperature) values of E. coli O157:H7, Salmonella , and L. monocytogenes at 55 to 70°C were 33.44 to 0.048 min, 45.87 to 0.083 min, and 47.17 to 0.085 min, respectively. The z (temperature rise for 1 log10 reduction of D) value of E. coli O157:H7, Salmonella , and L. monocytogenes in ground pork was 4.94°C, 5.89°C, and 5.92°C, respectively. Significant difference was found on the D and z values between E. coli O157:H7 and Salmonella or between E. coli O157:H7 and L. monocytogenes . The D and z values of Salmonella in ground pork were not significantly different from L. monocytogenes .     

MODELING THE INACTIVATION KINETICS OF ESCHERICHIA COLI O157:H7 DURING THE STORAGE UNDER REFRIGERATION OF APPLE JUICE TREATED BY PULSED ELECTRIC FIELDS

The aim was to describe the inactivation kinetics of Escherichia coli O157:H7 suspended in apple juice after pulsed electric fields (PEF) and a subsequent storage under refrigeration. Escherichia coli O157:H7 showed a great PEF resistance in apple juice, when survivors were evaluated immediately after PEF. However, PEF-treated cells exhibited a great sensitivity to a subsequent holding in apple juice for 3 days. For instance, although a PEF treatment of 80 pulses at 35.0 kV/cm inactivated less than 0.5 log₁₀ cell cycles, the maintenance of the samples up to 3 days at 4C caused an inactivation of 5.0 log₁₀ cycles. An equation based on the Weibullian-like distribution accurately described the kinetics of cell inactivation.

PRACTICAL APPLICATIONS

The storage time influences the pulsed electric fields (PEF) inactivation of Escherichia coli O157:H7 cells suspended in apple juice. The potential of Weibullian-like distributions to describe survival curves with deviations in their linearity has allowed us to obtain an equation that accurately describes the complete PEF survival profile of E. coli in apple juice, when survivors were evaluated immediately after PEF and also after a subsequent storage under refrigeration. These results underline the possibility of applying PEF to pasteurize acidic foods by taking into account the postprocessing effect of the acidity of the product.     

Mathematical Evaluation of Effective Moisture Diffusivity in Fresh Japanese Noodles (Udon) by Regular Regime Theory

The effect of moisture content and temperature on the effective moisture diffusivity was investigated to have the optimal drying condition of Japanese noodles (Udon) using regular regime theory. The drying of fresh Udon of different moisture contents was carried out under constant conditions of relative humidity and airflow at 20, 30, and 40 °C. The existence of regular regime periods for fresh noodles was experimentally verified. Effective moisture diffusivity obtained ranged from 2.1 × 10 ^-7 to 3.7 × 10 ^-7 cm² s^-1. The effect of temperature on effective moisture diffusivity was adequately modeled by the Arrhenius relationship, although the effect of moisture content was quite small.     

Inactivation of Escherichia coli O157:H7 and Escherichia coli 8739 in apple juice by pulsed electric fields.

The effect of high voltage pulsed electric field (PEF) treatment on Escherichia coli O157:H7 and generic E. coli 8739 in apple juice was investigated. Fresh apple juice samples inoculated with E. coli O157:H7 and E. coli 8739 were treated by PEF with selected parameters including electric field strength, treatment time, and treatment temperature. Samples were exposed to bipolar pulses with electric field strengths of 30, 26, 22, and 18 kV/cm and total treatment times of 172, 144, 115, and 86 micros. A 5-log reduction in both cultures was determined by a standard nonselective medium spread plate laboratory procedure. Treatment temperature was kept below 35 degrees C. Results showed no difference in the sensitivities of E. coli O157:H7 and E. coli 8739 against PEF treatment. PEF is a promising technology for the inactivation of E. coli O157:H7 and E. coli 8739 in apple juice.     

Moisture Diffusivity in Sponge Cake as Related to Porous Structure Evaluation and Moisture Content

ABSTRACT: Water diffusivity within sponge cake was determined at 5, 20, and 25 °C by identification from a water sorption kinetic and using a mathematical model based on Fick's 2nd law. Water diffusivity at 20 °C within sponge cake varied from 0.5 × 10^-10 m²/s to 7.5 × 10^-10 m²/s as a function of sponge cake moisture content. Influence of temperature on the concentration-dependent diffusivity was investigated. The activation energy was found to vary with sponge cake moisture content from 84 to 128 kj/mole. Effective diffusivity variations were correlated with the changes in microstructure of the material that was observed by using environmental scanning electron microscopy. The level of porosity in the material played a dominant role in determining the effective diffusivity.     

Apparent diffusivities of reducing sugars in potato strips blanched in water

The mechanism of reducing sugar losses was investigated in potatoes cut into 9.5 × 9.5 mm and 13 × 13 mm strips and blanched for 300–2400s at different temperatures between 70°C and 100°C. Experiments were carried out using large amounts of well-agitated water. Assuming no chemical reaction and using appropriate solutions of the unsteady state diffusion equation for square parallelpiped geometry, the apparent diffusivities, D_a, of reducing sugars in the potato matrix were determined at different temperatures. the incorporation of the dimensions of the strips in the solution of the diffusion equation was sufficient to explain the effect of size on losses. Values of D_a were found to be in the range 1.2 × 10^-11 1.7 × 10^-11 m²s^-1 and could be correlated with temperature according to the Arrhenius law.     

EFFECT OF MARINADE AND DRYING TEMPERATURE ON INACTIVATION OF ESCHERICHIA COLI O157:H7 ON INOCULATED HOME DRIED BEEF JERKY

Beef slices were inoculated (5.7–7.5 log CFU/cm²) with a 4-strain composite of E. coli O157:H7, stored (4C, 24 h), marinated (4C, 24 h), dried for 10 h at 62.5C or 68.3C, and stored for 90 days at 21C. Unmarinated beef slices dried for 10 h at 62.5C were used to determine the relative contribution of the marinate versus temperature treatment in the 62.5C trials. Samples were analyzed (bacterial enumeration with selective and nonselective agar media, pH, and a_w) following inoculation, marinating, at 4, 6, 8 and 10 h of drying, and after 30, 60 and 90 days of storage. Marination resulted in slight changes in bacterial populations (−0.3 to + 0.6 log CFU/cm²), but did not enhance bacterial reduction during drying. For all treatments, most bacterial reductions occurred in the first 4 h of drying, with little reduction thereafter. After 10 h of drying, bacterial reductions were 3.2–3.4 log CFU/cm² for unmarinated beef slices dried at 62.5C. Reductions of 2.2 and 3.0–4.6 log CFU/cm² were achieved in marinated jerky slices dried at 62.5C and 68.3C, respectively. No treatment resulted in the recommended 5-log reduction at the end of 10 h drying. However, bacteria did become undetectable by direct plating (<10 CFU/cm²) following 30 days of storage in all treatments except the unmarinated beef slices plated on tryptic soy agar (TSA). Additional work is needed to develop procedures for adequate destruction of E. coli O157:H7 during drying of beef jerky.     

Edible Apple Film Wraps Containing Plant Antimicrobials Inactivate Foodborne Pathogens on Meat and Poultry Products

ABSTRACT:  Apple-based edible films containing plant antimicrobials were evaluated for their activity against pathogenic bacteria on meat and poultry products.  Salmonella enterica  or  E. coli  O157:H7 (10⁷ CFU/g) cultures were surface inoculated on chicken breasts and  Listeria monocytogenes  (10⁶ CFU/g) on ham. The inoculated products were then wrapped with edible films containing 3 concentrations (0.5%, 1.5%, and 3%) of cinnamaldehyde or carvacrol. Following incubation at either 23 or 4 °C for 72 h, samples were stomached in buffered peptone water, diluted, and plated for enumeration of survivors. The antimicrobial films exhibited concentration-dependent activities against the pathogens tested. At 23 °C on chicken breasts, films with 3% antimicrobials showed the highest reductions (4.3 to 6.8 log CFU/g) of both  S. enterica  and  E. coli  O157:H7. Films with 1.5% and 0.5% antimicrobials showed 2.4 to 4.3 and 1.6 to 2.8 log reductions, respectively. At 4 °C, carvacrol exhibited greater activity than did cinnamaldehyde. Films with 3%, 1.5%, and 0.5% carvacrol reduced the bacterial populations by about 3, 1.6 to 3, and 0.8 to 1 logs, respectively. Films with 3% and 1.5% cinnamaldehyde induced 1.2 to 2.8 and 1.2 to 1.3 log reductions, respectively. For  L. monocytogenes  on ham, carvacrol films induced greater reductions than did cinnamaldehyde films at all concentrations tested. In general, the reduction of  L. monocytogenes  on ham at 23 °C was greater than at 4 °C. Added antimicrobials had minor effects on physical properties of the films. The results suggest that the food industry and consumers could use these films as wrappings to control surface contamination by foodborne pathogenic microorganisms.     

EFFECT OF SEVERAL EXPERIMENTAL PARAMETERS ON COMBINATION OF RED KIDNEY BEAN (PHASEOLUS VULGARIS) α-AMYLASE INHIBITOR WITH PORCINE PANCREATIC α-AMYLASE

Purified red kidney bean (Phaseolus vulgaris) amylase inhibitor forms a 1:1 stoichiometric complex with porcine pancreatic α-amylase leading to complete loss of enzyme activity on starch. Rate of complex formation is pH dependent and is maximal at pH 5. The rate constants for complex formation, as measured by loss of amylase activity, were 2.85 × 10⁴ M^-1 sec^-1 at pH 6.9 (ionic strength of 0.918) and 2.55 × 10⁵ M^-1 sec^-1 at pH 5 at 30°C. At pH 6.9, rate of complex formation was 4.8 times faster at 0.918 ionic strength as compared with the rate at 0.138 ionic strength. At 30°C, pH 6.9 and ionic strength of 0.168 the dissociation constant of the enzyme-inhibitor complex was determined to be 3.5 × 10^-11 M. The rate constant for dissociation of the complex was calculated to be 8.7 × 10^-8 sec^-1 under the same conditions. The rate constant for complex formation, at ionic strength of 0.168, was 1.1 × 10⁴ M^-1 sec^-1 at 37⁰ and 9.77 × 10² M^-1 sec^-1 at 25.7°C. The calculated activation energy for complex formation is 39.5 kcal/mole suggesting a rate-controlling conformational change. Oxidation of the carbohydrate moiety of the glycoprotein inhibitor caused complete loss of activity. Maltose, a competitive inhibitor of α-amylase, bound as readily to the enzyme-inhibitor complex as to free α-amylase. Trypsinized α-amylase, although still able to bind to Sephadex, did not bind inhibitor. The experiments with maltose and trypsinized amylase suggest the inhibitor may not bind at the active site of α-amylase.