David J Geveke

Eastern Idaho Regional Medical Center, Idaho Falls, Idaho, United States

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Publications (36)64.05 Total impact

  • F. Sampedro, A. McAloon, W. Yee, X. Fan, D. J. Geveke
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    ABSTRACT: The cost of high pressure processing (HPP) and the environmental impact of pulsed electric fields (PEF), HPP and thermal pasteurization of orange juice were estimated in the US. The cost analysis was based on commercial processing conditions that were validated for a 2-month shelf-life of orange juice under refrigeration conditions. Total electricity consumption was estimated to be 38,100 and 1,000,000 k Wh/year for thermal and HPP processing, respectively. Total pasteurization cost of HPP was estimated to be 10.7 ¢/l for processing 16,500,000 l/year (3,000 l/h). Of this, capital costs accounted for 59 % (6.3 ¢/l), labor costs accounted for 37 % (4.0 ¢/l) and utility charges, mainly electricity, accounted for 4 % (0.4 ¢/l). The total HPP cost was 7-folds higher than that of conventional thermal processing (1.5 ¢/l). The equivalent CO2 emission was 90,000 kg for thermal processing and 700,000 and 773,000 kg for PEF and HPP, respectively. This corresponds to an increase between 7- and 8-folds in comparison to the thermal processing. Increasing the production output by 2- to 6-folds reduced the total production costs of nonthermal processing by 50–75 %. A deeper knowledge of the processing costs and environmental impact of nonthermal technologies will afford companies a better understanding of the benefits and limitations of these novel systems.
    Food and Bioprocess Technology 07/2014; 7(7). · 4.12 Impact Factor
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    ABSTRACT: This paper investigated the feasibility for pasteurizing raw (100 %) pomegranate juice in a commercial scale pulsed electric field (PEF) processing system. The juice was processed at 35 and 38 kV/cm for 281 μs at 55 °C with a flow rate of 100 L/h. Effect of PEF processing on microbial stability, color, °Brix, pH, sediment, antioxidant activity, total phenolic content, anthocyanin, and sensory properties after the treatments and during storage at 4 °C for 12 weeks were studied and compared to those of thermally processed juice. PEF treatments significantly (p < 0.05) inhibited the growth of total aerobic bacteria, which remained at <2.5 log colony-forming units (CFU)/ml during the 12-week storage. No yeast and mold were detected (<0.69 log CFU/ml) in the PEF-treated juices during storage up to weeks 10 and 12, which is similar to the thermally processed juice. There were no significant differences in pH and °Brix values between the PEF processed juice and unprocessed juice. PEF processing did not alter the contents of total phenolics and anthocyanin as compared to unprocessed juice. PEF processing had significantly (p < 0.05) less impact on the color of pomegranate juice than thermal processing. PEF-treated juice had the same consumer satisfaction scores as the unprocessed juice, which were significantly (p < 0.05) higher than thermally processed juice samples. There was no significant difference between the two PEF treatments in all results. This study demonstrated that PEF technology extended microbial shelf-life and preserved the major quality and nutritional characteristics of pomegranate juice, and hence, is technically feasible for commercialization in the juice industry.
    Food and Bioprocess Technology 07/2014; 7(7). · 4.12 Impact Factor
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    ABSTRACT: This study compared the quality of fresh orange juice to that of supercritical carbon dioxide (SCCO2)‐processed juice and equivalently thermally processed juice in terms of microbial lethality. A pilot‐plant scale SCCO2 unit with a gas–liquid metal contactor processed juice with a CO2 concentration of ca. 8.5 wt % at 42C for 20 min. Thermal processing was conducted at 70C for 7.2 s. The number of naturally occurring microorganisms decreased from ca. 2.0–3.0 × 103 to 18–28 cfu/mL after both SCCO2 and thermal processing. No noticeable changes in pH, °Brix, titratable acidity and ascorbic acid content were observed between processed and unprocessed juice. SCCO2 and thermal processing inactivated 46.5 and 86.4% of pectin methylesterase, respectively. The cloud stability of the SCCO2‐processed juice was greatly enhanced compared with fresh and thermally processed juices. This study demonstrated that SCCO2 processing can improve the microbial quality of orange juice without deterioration, suggesting the potential for commercialization.
    Journal of Food Processing and Preservation 01/2014; 38(1). · 0.45 Impact Factor
  • David J Geveke, Daniel Torres
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    ABSTRACT: Studies are limited on UV nonthermal pasteurization of liquid egg white (LEW). The objective of this study was to inactivate Escherichia coli using a UV irradiator that centrifugally formed a thin film of LEW on the inside of a rotating cylinder. The LEW was inoculated with E. coli K12 to approximately 8log cfu/ml and was processed at the following conditions: UV intensity 1.5 to 9.0mW/cm(2); cylinder rotational speed 450 to 750RPM, cylinder inclination angle 15° to 45°, and flow rate 300 to 900ml/min, and treatment time 1.1 to 3.2s. Appropriate dilutions of the samples were pourplated with tryptic soy agar (TSA). Sublethal injury was determined using TSA+4% NaCl. The regrowth of surviving E. coli during refrigerated storage for 28days was investigated. The electrical energy of the UV process was also determined. The results demonstrated that UV processing of LEW at a dose of 29mJ/cm(2) at 10°C reduced E. coli by 5log cfu/ml. Inactivation significantly increased with increasing UV dose and decreasing flow rate. The results at cylinder inclination angles of 30° and 45° were similar and were significantly better than those at 15°. The cylinder rotational speed had no significant effect on inactivation. The occurrence of sublethal injury was detected. Storage of UV processed LEW at 4° and 10°C for 21days further reduced the population of E. coli to approximately 1log cfu/ml where it remained for an additional 7days. The UV energy applied to the LEW to obtain a 5 log reduction of E. coli was 3.9J/ml. These results suggest that LEW may be efficiently pasteurized, albeit at low flow rates, using a nonthermal UV device that centrifugally forms a thin film.
    International journal of food microbiology 12/2012; 162(1):43-47. · 3.01 Impact Factor
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    ABSTRACT: The most recent outbreak of listeriosis linked to consumption of fresh-cut cantaloupes indicates the need to investigate the behavior of Listeria monocytogenes in the presence of native microflora of cantaloupe pieces during storage. Whole cantaloupes were inoculated with L. monocytogenes (10(8)-CFU/ml suspension) for 10 min and air dried in a biosafety cabinet for 1 h and then treated (unwashed, water washed, and 2.5% hydrogen peroxide washed). Fresh-cut pieces (∼3 cm) prepared from these melons were left at 5 and 10°C for 72 h and room temperature (20°C) for 48 h. Some fresh-cut pieces were left at 20°C for 2 and 4 h and then refrigerated at 5°C. Microbial populations of fresh-cut pieces were determined by the plate count method or enrichment method immediately after preparation. Aerobic mesophilic bacteria, yeast and mold of whole melon, and inoculated populations of L. monocytogenes on cantaloupe rind surfaces averaged 6.4, 3.3, and 4.6 log CFU/cm(2), respectively. Only H(2)O(2) (2.5%) treatment reduced the aerobic mesophilic bacteria, yeast and mold, and L. monocytogenes populations to 3.8, 0.9, and 1.8 log CFU/cm(2), respectively. The populations of L. monocytogenes transferred from melon rinds to fresh-cut pieces were below detection but were present by enrichment. Increased storage temperatures enhanced the lag phases and growth of L. monocytogenes. The results of this study confirmed the need to store fresh-cut cantaloupes at 5°C immediately after preparation to enhance the microbial safety of the fruit.
    Journal of food protection 11/2012; 75(11):1912-9. · 1.83 Impact Factor
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    ABSTRACT: A study was conducted to identify sanitizing solutions effective at inactivating ca. 5logCFU of Salmonella enterica inoculated onto the stem scar of red round tomatoes during two-minute immersion treatments. Sixty-three antimicrobial combinations were tested. Vacuum perfusion was applied to tomatoes during selected treatments to promote infiltration of sanitizer into porous tomato stem scar tissue. Red round tomatoes were inoculated to ca. 6.9logCFU/stem scar with a four-serovar composite of Salmonella enterica, air dried, and tomatoes were immersed in circulating sanitizing solutions for 120s at ca. 22°C. Stem scars were aseptically excised, macerated in DE neutralizing broth, and the homogenate was spiral plated. Twenty-four washes inactivated ≥3.0logCFU/stem scar. Seven treatments reduced ≥4.8 log (viz., 40% EtOH, sulfuric acid, and organic acid combinations). LogCFU/stem scar reductions for various sanitizers are listed in parenthesis, as follows: 90ppm peroxyacetic acid (1.31), 200ppm chlorine (1.53), 190ppm chlorine+15″ Hg vacuum perfusion (2.23), 0.2N sodium hydroxide (NaOH) (3.78), 2% total of lactic+acetic acid (4.35), 3% total of phosphoric+lactic acids (4.51), and 40% ethanol (4.81). Solutions that achieved ≥4.95 log reductions were 5.1% total of lactic+acetic+levulinic acids, 49% ethanol, 6% total of lactic+acetic acids, and a 0.2M H(2)SO(4) (sulfuric acid) solution. The use of vacuum perfusion with 200ppm chlorine increased inactivation by 0.7logCFU over chlorine alone, however, P>0.05. Results from this study provide tomato processers with some sanitization options effective at inactivating Salmonella from the stem scars of tomatoes. These results may also help processors and scientists design future decontamination studies by incorporating combinations of these chemical treatments.
    International journal of food microbiology 10/2012; 159(2):84-92. · 3.01 Impact Factor
  • David J. Geveke, Daniel Torres
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    ABSTRACT: Studies are lacking on the nonthermal pasteurization of liquid foods using UV irradiators that centrifugally form very thin films to overcome the problem of limited penetration depth of UV. Grapefruit juice inoculated with Escherichia coli or Saccharomyces cerevisiae was processed at the following conditions: UV dose 4.8–24 mJ/cm2; treatment time 3.2 s, cylinder rotational speed 450–750 rpm, cylinder inclination angle 15–45°, outlet temperature 11 °C, and flow rate 300 ml/min, and was stored for 35 days. Appropriate dilutions of the samples were pour plated with TSA and TSA + 3% NaCl for E. coli and Sabouraud dextrose agar (SDA) and SDA + 5% NaCl for S. cerevisiae. Nonthermal UV processing at 19 mJ/cm2, 450 rpm and 15° reduced E. coli in grapefruit juice by 5.1 log10. A dose of 14 mJ/cm2 reduced S. cerevisiae by 6.0 log10. Inactivation increased linearly with increasing UV dose. The inactivations at 600 and 750 rpm were similar, and were better than at 450 rpm. The results at 30° and 45° were similar, and were better than at 15°. The occurrence of sublethal injury in either microorganism was not detected. Storing UV processed grapefruit juice at 4 and 10 °C reduced the surviving E. coli to below 1 log10 cfu/ml in 14 days. Processing UV juice reduced the population of S. cerevisiae to less than 1 log10 cfu/ml where it remained for 35 days during refrigerated storage. These results suggest that grapefruit juice may be pasteurized using a nonthermal UV irradiator that centrifugally forms a thin film.
    Journal of Food Engineering. 07/2012; 111(2):241–246.
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    ABSTRACT: This study investigated the antimicrobial effect of a chitosan coating+allyl isothiocyanate (AIT) and nisin against Salmonella on whole fresh cantaloupes. Cantaloupes were inoculated with a cocktail of three Salmonella strains and treated with chitosan, chitosan+AIT, chitosan+nisin, and chitosan+AIT+nisin coatings. With AIT concentrations increasing from 10 to 60 μl/ml, the antibacterial effects of coating treatments against Salmonella increased. Chitosan coatings with 60 μl/ml AIT (chitosan+60AIT) reduced more than 5 log₁₀ CFU/cm² of Salmonella. The addition of nisin to the chitosan-AIT coating synergistically increased the antibacterial effect; coatings with nisin (25 mg/ml or 25,000 IU/ml)+30 μl/ml AIT resulted in a 4.8 log₁₀ reduction of Salmonella. The chitosan+60AIT coating significantly (p<0.05) reduced populations of native bacteria on cantaloupes to ca. 2 log₁₀ CFU/cm² during the first 6 days and populations remained unchanged through day 14 at 10 °C. The same coating treatment completely inactivated mold and yeast on cantaloupe at day 1 and no regrowth occurred even up to 14 days of storage. Scanning electron microscopy revealed that cell membrane damage and leakage of intercellular components occurred as a result of the chitosan-AIT coating treatments. No visual changes in overall appearance and color of cantaloupe rind and flesh due to coating treatments were observed. These results indicate that the application of an antimicrobial coating may be an effective method for decontamination of cantaloupes.
    International journal of food microbiology 02/2012; 155(3):165-70. · 3.01 Impact Factor
  • Hyun-Gyun Yuk, David J Geveke
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    ABSTRACT: The objective of this study was to evaluate the efficacy of supercritical carbon dioxide (SCCO(2)) for inactivating Lactobacillus plantarum in apple cider using a continuous system with a gas-liquid metal contactor. Pasteurized apple cider without preservatives was inoculated with L. plantarum and processed using a SCCO(2) system at a CO(2) concentration range of 0-12% (g CO(2)/100g product), outlet temperatures of 34, 38, and 42 °C, a system pressure of 7.6 MPa, and a flow rate of 1 L/min. Processing with SCCO(2) significantly (P<0.05) enhanced inactivation of L. plantarum in apple cider, resulting in a 5 log reduction with 8% CO(2) at 42 °C. The response surface model indicated that both CO(2) concentration and temperature contributed to the microbial inactivation. The extent of sublethal injury in surviving cells in processed apple cider increased as CO(2) concentration and processing temperature increased, however the percent injury dramatically decreased during SCCO(2) processing at 42 °C. Structural damage in cell membranes after SCCO(2) processing was observed by SEM. Refrigeration (4 °C) after SCCO(2) processing effectively inhibited the re-growth of surviving L. plantarum during storage for 28 days. Thus this study suggests that SCCO(2) processing is effective in eliminating L. plantarum and could be applicable for nonthermal pasteurization of apple cider.
    Food Microbiology 05/2011; 28(3):377-83. · 3.41 Impact Factor
  • DAVID J. GEVEKE, GLENN BOYD, HOWARD Q. ZHANG
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    ABSTRACT: Knowledge of penetration depth of ultraviolet light (UV) in liquid egg is crucial in designing nonthermal UV pasteurizers. An experimental method was developed to determine penetration depth of 254 nm UV in liquid whole egg (LWE) and liquid egg white (LEW). The UV that penetrated through the egg was measured by a radiometer. Penetration depth, where the intensity of the UV decreases to 37% of the value at the surface, was 0.0066 cm and 0.0085 cm for LWE and LEW, respectively. This study indicates that in order to process liquid egg products with UV, thin films of 0.01 cm to 0.02 cm depth may be required.PRACTICAL APPLICATIONSThe safety and quality of liquid egg products could benefit from being nonthermally pasteurized by ultraviolet light (UV); however, data on the penetration depth of UV in egg are extremely limited. An experimental method was developed to determine the penetration depth of UV in liquid whole egg (LWE) and liquid egg white (LEW). The penetration depth was 0.0066 cm and 0.0085 cm for LWE and LEW, respectively. The results of this study indicate that thin films of 0.01 cm to 0.02 cm depth may be required to effectively process liquid egg products with UV. This information will aid in the design of nonthermal UV pasteurizers that may well produce egg products that have better quality than those currently available using thermal pasteurization.
    Journal of Food Processing and Preservation 04/2011; 35(6):754 - 757. · 0.45 Impact Factor
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    ABSTRACT: Current FDA regulations require that juice processors achieve a 5 log CFU/ml reduction of a target pathogen prior to distributing products. Whereas thermal pasteurization reduces the sensory characteristics of juice, pulsed electric field (PEF) treatments can be conducted at lower temperatures and may preserve sensory characteristics.Escherichia coli O157:H7 (ATCC 43895) and a non-pathogenic E. coli (ATCC 35218), respectively, were inoculated into single-strength strawberry juice with or without 750 ppm sodium benzoate (SB), 350 ppm potassium sorbate (PS), and 2.7% citric acid (CA). Juice was treated at outlet temperatures of 45, 50 and 55 °C at a field strength of 18.6 kV/cm for 150 μs with a laboratory-scale PEF unit. Inactivation of surrogate E. coli at 45, 50, and 55 °C were 2.86, 3.12, and 3.79 log CFU/ml, respectively, in plain juice (pH 3.4), and 2.75, 3.52, and 5.11 with the addition of benzoic and sorbic acids (pH 3.5). Inactivation of E. coli O157:H7 under the same conditions were 3.09, 4.08, and 4.71 log CFU/ml, respectively, and 2.27, 3.29, and 5.40 with antimicrobials. E. coli O157:H7 in juice with antimicrobials and 2.7% CA (pH 2.7) treated with PEF was reduced by 2.60, 4.32 and 6.95 log CFU/ml at 45, 50 and 55 °C while the surrogate E. coli decreased by 3.54, 5.69, and 7.13 log under the same conditions. When juice (pH 2.7) was held for 6 h without PEF treatment, higher numbers of E. coli 35218 (7.17 log CFU/ml) were inactivated than of acid-resistant E. coli O157:H7 (3.89 log). Slightly greater PEF inactivation of E. coli O157:H7 than of the surrogate bacterium indicates that E. coli ATCC 35218 provides a margin of safety when used as a surrogate for O157:H7 in plain strawberry juice or in juice + SB + PS at 45–50 °C, or with SB + PS and CA at 55 °C.
    Food Control. 01/2011; 22(10):1689-1694.
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    ABSTRACT: Three processing techniques: heat, pulsed electric field (PEF) and ultraviolet (UV) light were optimized to achieve a similar 6 log reduction of inoculated Escherichia coli K12 in apple cider. Microbial populations (total aerobic and yeast and mold), sensory, color and physical properties (pH and°Brix) of processed apple cider were investigated during 4-week storage at 4C. PEF and thermally processed cider maintained good microbial quality during 4 weeks of storage while UV-treated cider showed a significant (P < 0.05) growth in yeast and mold after 2 weeks of storage. As a result,°Brix value decreased significantly (P < 0.05) for UV cider after 4 weeks of storage. Apple cider pH was neither affected by any treatment nor by storage. Thermal and UV-pasteurized ciders faded significantly (P < 0.05) during storage (International Commission on Illumination L*[lightness] and b*[yellow] values increased) compared to PEF cider. Triangle sensory analysis indicated a significant difference (P < 0.05) in aroma between treatments. PEF-treated cider was preferred over thermal and UV cider by sensory panelists at the end of the storage period. The results suggested that PEF-treated apple cider had a longer shelf life than UV-treated cider and a better aroma and color than thermally processed sample.PRACTICAL APPLICATIONSNonthermal processes like pulsed electric field (PEF) and ultraviolet (UV) light are developed as alternative pasteurization technologies to heat for their efficacy to extend shelf life and enhance the safety of fresh juice while preserving organoleptic and nutritional qualities. For fair comparison of the effects on quality of juice, both thermal and nonthermal processes must achieve equivalent reduction in microorganism levels. In the present study, the effect of PEF, UV and thermal techniques on apple cider quality are compared at conditions optimized to achieve equivalent 6 log reductions in Escherichia coli. Our results showed that PEF extended the shelf-life of apple cider by inactivating spoilage microorganisms compared to UV processing, and better preserved the freshness (aroma and color) over traditional thermal processing. Based on these results, PEF process is the best choice among the three technologies studied.
    Journal of Food Quality 10/2010; 33(5):612 - 631. · 0.76 Impact Factor
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    Hyun-Gyun Yuk, David J Geveke, Howard Q Zhang
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    ABSTRACT: This study evaluated the efficacy of a supercritical carbon dioxide (SCCO(2)) system with a gas-liquid porous metal contactor for eliminating Escherichia coli K12 in apple cider. Pasteurized, preservative-free apple cider was inoculated with E. coli K12 and processed using the SCCO(2) system at CO(2) concentrations of 0-10% (wt.%, g CO(2)/100g product), outlet temperatures of 34, 38, and 42 degrees C, a system pressure of 7.6 MPa, and a flow rate of 1L/min. Increased CO(2) concentrations and temperatures significantly (P<0.05) enhanced the bactericidal effect, resulting in a maximum reduction of 7.31 log CFU/mL at 8% CO(2) and 42 degrees C. A response surface model indicated that minimum CO(2) concentrations of 9.9% at 34 degrees C, 7.4% at 38 degrees C, and 5.4% at 42 degrees C are needed to achieve a 5-log reduction of E. coli K12 in apple cider. SEM observations showed morphological changes in the cell envelope after SCCO(2) processing. At a processing condition of 8% and 38 degrees C, the reduction of E. coli was 6.03 log and the sublethal injury of the survivors was 84%. The regrowth or survival of E. coli in SCCO(2) processed apple cider was not observed during storage for 28 days at 4, 8, and 20 degrees C. Thus this study showed the potential of SCCO(2) processing with a gas-liquid porous metal contactor for the nonthermal pasteurization of apple cider.
    International journal of food microbiology 03/2010; 138(1-2):91-9. · 3.01 Impact Factor
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    Dike O Ukuku, David J Geveke
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    ABSTRACT: Radio frequency electric fields (RFEF) and UV-light treatments have been reported to inactivate bacteria in liquid foods. However, information on the efficacy of bacterial inactivation by combined treatments of RFEF and UV-light technologies is limited. In this study, we investigated the relationship between cell injury and inactivation of Escherichia coli K-12 in apple juice treated with a combination of RFEF and UV-light. Apple juice purchased from a wholesale distributor was inoculated with E. coli K-12 at 7.8 log CFU/ml, processed with a laboratory scale RFEF unit at 20 kHz, 15 kV/cm for 170 micros at a flow rate of 540 ml/min followed by UV-light treatment (254 nm) for 12s at 25, 30 and 40 degrees C. Treated samples were analyzed for leakage of UV-substances as a function of membrane damage and were plated (0.1 ml) on Sorbitol MacConkey Agar (SMAC) and Trypticase Soy Agar (TSA) plates to determine the viability loss and percent injury. At 40 degrees C, UV-light treatment alone caused 5.8 log reduction of E. coli in apple juice while RFEF caused only 2.8 log reduction. A combination of the two processing treatments did not increase cell injury or leakage of intracellular bacterial UV-substances more than that from the UV-light treatment. Similarly, the viability loss determined was not significantly (P<0.05) different than UV-light treatment alone. However, the UV-substances determined in apple juice treated with RFEF was significantly (P>0.05) different than UV-light treated samples. The results of this study suggest that RFEF treatment causes more injury to the bacterial cells leading to more leakage of intracellular UV-substances than cells treated with UV-light alone. Also, the effect of the two processing treatment combination on bacterial inactivation was not additive.
    International journal of food microbiology 03/2010; 138(1-2):50-5. · 3.01 Impact Factor
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    ABSTRACT: Pulsed electric field (PEF) technology has been used for the inactivation of microorganisms and to prevent flavor loss in liquid foods and beverages in place of thermal pasteurization. When used to pasteurize orange juice, PEF may prevent loss of volatile sensory attributes. Enterohemorrhagic E. coli O157:H7 (EHEC), two strains of Salmonella Typhimurium, and twenty strains of non-pathogenic bacteria were screened for inactivation in orange juice by PEF at 22 and 20kV/cm at 45 and 55 degrees C, respectively. Higher populations of both salmonellae were inactivated (2.81 and 3.54 log CFU/ml) at 55 degrees C, in comparison with the reduction of EHEC (2.22 log). When tested under the same conditions, inactivation of EHEC was slightly greater than that of a non-pathogenic E. coli (NPEC) ATCC 35218 (2.02 log). NPEC was further tested as a surrogate for EHEC by comparing inactivation kinetics at 45, 50 and 55 degrees C at field strengths of between 7.86 and 32.55kV/cm. Statistical comparison of revealed that EHEC and NPEC inactivation curves were homogeneous at outlet temperatures of 45 and 50 degrees C; however, EHEC was slightly more sensitive to PEF than the surrogate NPEC at 55 degrees C. The higher PEF resistance of non-pathogenic E. coli 35218 at 55 degrees C may provide a desirable margin of safety when used in pilot plant challenge studies in place of E. coli O157:H7.
    International journal of food microbiology 02/2010; 139(1-2):1-8. · 3.01 Impact Factor
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    ABSTRACT: This study was conducted to compare thermal inactivation kinetics obtained using a pilot-scale pasteurizer and a bench-scale processing system. Pilot-scale pasteurizers are useful for product development, but comparisons on thermal inactivation kinetics with smaller scale systems are lacking. Using an Armfield pilot-scale pasteurizer and aluminum thermal-death-time (TDT) disks, the D-values and z-values of Escherichia coli K12 in apple cider were determined in the temperature range of 54–62°C. Come-up times to 58°C were also measured and were 35 and 61s for the TDT disks and pasteurizer, respectively. The D-values from the TDT disks were 9.66, 4.01, 1.44 and 0.44min at temperatures of 54, 56, 58, and 60°C, respectively. The D-values from the pasteurizer were 3.48, 1.22, 0.10 and 0.05min at temperatures of 56, 58, 60, and 62°C, respectively. The z-values from the TDT disks and the pasteurizer were 4.68 and 3.60°C, respectively. There was no significant (P>0.05) difference in the D-values of the TDT disks and pasteurizer at 56 and 58°C, while there was a significant (P
    Food Control 11/2009; · 2.74 Impact Factor
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    Hyun-Gyun Yuk, David J. Geveke, Howard Q. Zhang
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    ABSTRACT: This study evaluated the effectiveness of a supercritical carbon dioxide (SCCO2) system, with a gas–liquid porous metal contactor, for reducing Escherichia coli K12 in diluted buffered peptone water. 0.1% (w/v) buffered peptone water inoculated with E. coli K12 was processed using the SCCO2 system at CO2 concentrations of 3.1–9.5 wt%, outlet temperatures of 34, 38, and 42 °C, a system pressure of 7.6 MPa, and a flow rate of 1 L/min. Increased CO2 concentrations and temperatures significantly (P < 0.05) enhanced microbial reduction. A maximum reduction of 5.8-log was obtained at 8.2% CO2 and 42 °C. To achieve a 5-log reduction of E. coli K12 in 0.1% buffered peptone water, minimum CO2 concentrations of 9.5%, 5.5%, and 5.3% were needed at 34, 38, and 42 °C, respectively. Further reductions of cells were observed after storage for 7 days at 4 °C. But storage at 25 °C increased the number of viable cells to 8-log cfu/mL after 7 days. This study showed the potential of the pilot scale SCCO2 system with a gas–liquid porous metal contactor for microbial inactivation in liquid food.
    Food Control 09/2009; · 2.74 Impact Factor
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    ABSTRACT: Listeria monocytogenes, a psychrotrophic foodborne pathogen, is a recurring postprocess contaminant on ready-to-eat meat (RTE) products including frankfurters. Flash (Steam) Pasteurization (FP) and ultraviolet light (254 nm-UVC) has been shown to reduce levels of L. monocytogenes and L. innocua on frankfurters. In this study, the use of UVC light followed by FP to inactivate L. innocua, a nonpathogenic surrogate for L.monocytogenes, on frankfurters that contained sodium diacetate and potassium lactate (SDA/PL) in a pilot-plant setting was investigated. Application of UVC (1.0 J/cm2), followed by FP (0.75 s steam/121 degrees C) resulted in inactivation of 3.19 log L. innocua, while application of UVC (4.0 J/cm2), followed by FP (3 s steam/121 degrees C) resulted in inactivation of 3.89 log of L. innocua. A refrigerated storage study (8 degrees C) of frankfurters that contained SDA/PL that were treated with UVC followed by FP revealed the growth of L. innocua was inhibited for approximately 8 wk following application of the interventions. The use of UVC in combination with FP had little effect on frankfurter color and texture. The combination of UVC, FP, and SDA/PL was found to be an effective hurdle process for decontamination of frankfurter surfaces.
    Journal of Food Science 05/2009; 74(3):M138-41. · 1.78 Impact Factor
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    ABSTRACT: The effect of thermal and pulsed electric field (PEF) processing on the shelf life of an orange juice-milk beverage (OJMB) was studied. The intensities of the treatments were selected to produce similar inactivation of pectin methyl esterase (PME), an enzyme responsible for the jellification and loss of fresh juice cloudiness. Physical properties (pH, degrees Brix, and color), microbial population, PME activity, and volatile compounds of the product were analyzed during a 4-wk storage at 8 to 10 degrees C. The pH was not affected by any treatment but decreased during the storage in the untreated sample. The degrees Brix values were decreased by the 2 treatments. The thermal and PEF treatments initially inactivated PME activity by 90%. During storage, the PME activity remained constant in the 2 treated samples and decreased slightly in the untreated sample. The reductions in bacterial as well as yeast and mold counts were similar after the 2 treatments (4.5 and 4.1 log CFU/mL for thermal against 4.5 and 5 log CFU/mL for PEF). Based on the initial bacterial counts of the control, it was estimated that the shelf lives of the OJMB treated with thermal and PEF processing stored at 8 to 10 degrees C were 2 and 2.5 wk, respectively. Differences were observed in the color parameters of the OJMB between the 2 treatments in comparison with the control, with a higher difference observed in the thermally processed samples. The relative concentration of volatile compounds was higher in OJMB processed by PEF treatment than that in the thermally processed sample. During storage, the loss of volatile compounds was lower in the PEF sample while thermal and control samples had a similar rate of loss. For an OJMB, treatment with PEF achieved the same degree of microbial and enzyme inactivation as the thermal treatment, but better preserved color and volatile compounds.
    Journal of Food Science 04/2009; 74(2):S107-12. · 1.78 Impact Factor
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    David J Geveke, Joshua Gurtler, Howard Q Zhang
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    ABSTRACT: Radio frequency electric fields (RFEF) nonthermal processing effectively inactivates gram-negative bacteria in juices, but has yet to be shown effective at reducing gram-positive bacteria. Apple cider containing Lactobacillus plantarum ATCC 49445, a gram-positive bacterium, was RFEF processed under the following conditions: field strength of 0.15 to 15 kV/cm, temperature of 45 to 55 degrees C, frequency of 5 to 65 kHz, treatment time of 170 micros, and holding time of 5 to 50 s. The effect of refrigerating the inoculated cider prior to processing, the extent of sublethal injury, and the effect of storing the treated cider for 35 days were investigated. The population of L. plantarum was reduced by 1.0 log at 15 kV/cm, 20 kHz, and 50 degrees C, with a 5-s hold time. There is a synergistic effect between RFEF and heat above 50 degrees C. Inactivation significantly (P < 0.05) increased as frequency was decreased from 65 to 5 kHz. Inactivation increased linearly with field above 8 kV/cm. Holding cider at 55 degrees C after RFEF treatment for 5 and 50 s resulted in 2.5- and 3.1-log reductions, respectively. The surviving population was composed of 1.4-log sublethally injured cells. Storing processed cider at 4 degrees C for 35 days steadily and significantly (P < 0.05) reduced L. plantarum from 4.5 to 0.9 log CFU/ml. The electrical energy density was 51 J/ml. This provides the first evidence that nonthermal RFEF processing inactivates gram-positive bacteria, and that surviving cells may die off during refrigerated storage.
    Journal of food protection 03/2009; 72(3):656-61. · 1.83 Impact Factor

Publication Stats

179 Citations
64.05 Total Impact Points

Institutions

  • 2002–2012
    • Eastern Idaho Regional Medical Center
      Idaho Falls, Idaho, United States
  • 2011
    • National University of Singapore
      • Department of Chemistry
      Singapore, Singapore
  • 2007–2010
    • United States Department of Agriculture
      • Agricultural Research Service (ARS)
      Washington, D. C., DC, United States
  • 2002–2008
    • Princeton University
      • Princeton Plasma Physics Laboratory
      Princeton, New Jersey, United States