Ahmed E Yousef

The Ohio State University, Columbus, Ohio, United States

Are you Ahmed E Yousef?

Claim your profile

Publications (112)211.67 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Peanut safety and quality were evaluated for different roasting technologies. Shelled raw peanuts were roasted using an oven at 163 to 204 °C, microwave, or oven and microwave combinations. The lethal effect of these treatments was investigated on peanuts inoculated with the Salmonella surrogate, Enterococcus faecium and stored at room temperature for 1 h, 24 h, or 7 d before roasting. Roasted peanut color, odor activity values (OAVs), descriptive sensory panel analysis, free fatty acid, and peroxide values were determined. Color and OAVs were also analyzed on 2 commercial peanut butters. OAVs were calculated using volatile levels quantified with selected ion flow tube mass spectrometry and known odor thresholds. All treatments resulted in a minimum of 3 log reduction of inoculated bacterial population. Resistance to the process was not influenced by storage of inoculated peanuts prior to treatment. Roasting by different methods produced equivalent, commercially ideal L* color. Based on the OAVs, treatments had similar volatiles important to flavor compared to the commercial samples. Descriptive sensory analysis showed no significant difference between the roasting treatments for most of the sensory attributes. Lipid oxidation was not significantly different between the roasting methods, displaying no evidence that roasting time or temperature affected lipid oxidation, when ideal color was produced. These results suggest that oven, microwave, or combination roasting should be sufficient to mitigate the threat of Salmonella contamination and produce similar color, OAVs, sensory attributes, and lipid oxidation results.Practical ApplicationPeanut safety is important especially since Salmonella outbreaks in tree nut and peanut products have been numerous in recent years. Roasted peanut color, odor activity values, lipid oxidation, and sensory attributes are quality parameters used to evaluate roasted peanuts. Based on the evaluated safety and quality parameters, microwave or microwave and oven combination roasting technologies may be used as alternative roasting methods to produce peanut butter potentially decreasing the production costs.
    Journal of Food Science 07/2014; · 1.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to investigate the effect of osmotic shock and adaptation at low water activity (aw) and the type of humectant used to lower the aw, on heat resistance of three Salmonella enterica serovars (Saintpaul 02-109, Tennessee 2053H, and Elmsbuettel 1236H). The serovars were grown (adapted) or transferred (osmotic shocked) in low-aw broths and subjected to heat treatment at 55°C for up to 45 min; samples were removed at 5-min intervals and immediately placed in an ice-water bath until plating. The aw of tryptic soy broth (TSB) was lowered by the addition of 20% (wt/wt) glycerol (aw 0.94), 4% (wt/wt) sodium chloride (NaCl; aw 0.97), or 35% sucrose (wt/wt) (aw 0.95). The type of humectant and cell adaptation significantly affected the D55°C-value. Cells merely suspended in 20% glycerol broth (i.e., nonadapted) prior to heat treatment showed a larger D55°C-value (3.0 to 3.9 min), when compared with that of cells adapted in the same medium (D55°C-values of 0.86 to 0.98 min). Interestingly, cells adapted to TSB plus glycerol were not more resistant to heat than were the controls. NaCl and sucrose showed a net protective effect for all serovars under both the adapted and nonadapted conditions, with sucrose providing the most protection. Highest D55°C-values were obtained for cultures adapted to TSB plus sucrose. Based on these results, the effect of reduced aw on thermal resistance of Salmonella serovars varies greatly, depending on medium constituents and adaptation of the pathogen in these media.
    Journal of food protection 06/2014; 77(6):914-8. · 1.83 Impact Factor
  • En Huang, Ahmed E Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: Paenibacterin, produced by Paenibacillus thiaminolyticus OSY-SE, is active both against Gram-negative and Gram-positive pathogens, including antibiotic-resistant strains of Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus and Enterococcus faecalis. Paenibacterin showed relatively low cytotoxicity against a human kidney cell line (ATCC CRL-2190), with a 50% inhibitory concentration (IC50)≥109μg/mL. The cationic paenibacterin molecule binds to the negatively charged Gram-negative endotoxins in vitro, suggesting that paenibacterin can neutralise lipopolysaccharides. In a murine septic shock model, two 500μg doses of paenibacterin significantly increased the survival of mice challenged with a lethal level of P. aeruginosa. Considering that paenibacterin is effective against many strains of antibiotic-resistant pathogens, this study suggests that this antimicrobial agent is a promising candidate as a new drug.
    International journal of antimicrobial agents 04/2014; · 3.03 Impact Factor
  • En Huang, Ahmed E Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: Paenibacterin is a new broad-spectrum lipopeptide antimicrobial agent produced by Paenibacillus thiaminolyticus OSY-SE. The compound consists of a cyclic 13-residue peptide and an N-terminal C15 fatty acyl chain. The mechanism of action of paenibacterin against Escherichia coli and Staphylococcus aureus was investigated in this study. The cationic lipopeptide, paenibacterin, showed a strong affinity to the negatively-charged lipopolysaccharides (LPS) from the outer membrane of Gram-negative bacteria. Addition of LPS (100 μg/ml) completely eliminated the antimicrobial activity of paenibacterin against E. coli. The electrostatic interaction between paenibacterin and LPS may have displaced the divalent cations on the LPS network and thus facilitated the uptake of antibiotic into Gram-negative cells. Paenibacterin also damaged bacterial cytoplasmic membrane as evidenced by the depolarization of membrane potential and leakage of intracellular potassium ions from cells of E. coli and S. aureus. Therefore, the bactericidal activity of paenibacterin is attributed to disruption of the outer membrane of Gram-negative bacteria and damage of the cytoplasmic membrane of both Gram-negative and Gram-positive bacteria. Despite the evidence of membrane damage, this study does not rule out additional bactericidal mechanisms potentially exerted by paenibacterin.
    Applied and Environmental Microbiology 02/2014; · 3.95 Impact Factor
  • En Huang, Yaoqi Guo, Ahmed E. Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: Paenibacterin is a novel lipopeptide antibiotic with potent activity against Gram-negative and Gram-positive human pathogens. The antibiotic consists of a cyclic 13-residue peptide and an N-terminal C15 fatty acyl chain. To elucidate the biosynthesis of paenibacterin, we determined the whole genome sequence of the producer strain Paenibacillus thiaminolyticus OSY-SE, and the function of the peptide synthetase was confirmed experimentally. The gene cluster of paenibacterin was identified within a 52-kb DNA region, encoding thee non-ribosomal peptide synthetases, PbtA, PbtB and PbtC, and two ABC-transporters, PbtD and PbtE. Both PbtA and PbtB consist of five modules, whereas PbtC comprises thee modules. Each of these 13 modules consists of thee essential domains (condensation-adenylation-thiolation) and assembles an amino acid into the paenibacterin peptide. Selected adenylation domains in the NRPS were cloned and expressed in Escherichia coli; the substrate specificity of each recombinant A-domain was studied in vitro by protein function analysis. The presence of four epimerization domains in paenibacterin peptide synthetases suggests that Orn1, Orn4, Lys7 and Ser8 in the paenibacterin molecule have D-configuration; the absolute configuration of two ornithine residues in paenibacterin was confirmed by chiral amino acid analysis using Marfey's reagents. Taken together, the findings enabled us to propose the biosynthetic pathway of paenibacterin.
    Research in Microbiology 01/2014; · 2.89 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To accomplish continuous flow ohmic heating of a low-acid food product, sufficient heat treatment needs to be delivered to the slowest-heating particle at the outlet of the holding section. This research was aimed at developing mathematical models for sterilization of a multicomponent food in a pilot-scale ohmic heater with electric-field-oriented parallel to the flow and validating microbial inactivation by inoculated particle methods. The model involved 2 sets of simulations, one for determination of fluid temperatures, and a second for evaluating the worst-case scenario. A residence time distribution study was conducted using radio frequency identification methodology to determine the residence time of the fastest-moving particle from a sample of at least 300 particles. Thermal verification of the mathematical model showed good agreement between calculated and experimental fluid temperatures (P > 0.05) at heater and holding tube exits, with a maximum error of 0.6 °C. To achieve a specified target lethal effect at the cold spot of the slowest-heating particle, the length of holding tube required was predicted to be 22 m for a 139.6 °C process temperature with volumetric flow rate of 1.0 × 10(-4) m(3) /s and 0.05 m in diameter. To verify the model, a microbiological validation test was conducted using at least 299 chicken-alginate particles inoculated with Clostridium sporogenes spores per run. The inoculated pack study indicated the absence of viable microorganisms at the target treatment and its presence for a subtarget treatment, thereby verifying model predictions.
    Journal of Food Science 11/2013; 78(11):E1721-E1734. · 1.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To ensure sterility of a solid–liquid mixture processed in continuous-flow ohmic systems, the slowest-heating solid particle needs to receive sufficient heat treatment at the outlet of the holding section. We describe herein, the development of a mathematical model for solid–liquid mixtures in a commercial ohmic heater with electric field oriented perpendicular to the flow. The fastest moving particle velocity was identified using over 299 particles and a radio-frequency identification technique, and used as an input to the model for the worst-case heating scenario. Thermal verification was conducted by comparing predicted and measured fluid temperatures at heater and hold tube outlets; the model showed good agreement between calculated and experimental fluid temperatures (P > 0.05) with a maximum error of 0.4 °C. The model predicted a hold tube length of 15.85 m at 134.0 °C process temperature to achieve a target lethal effect at the cold spot of the slowest-heating particle. Using this length of hold tube, microbiological tests were conducted using at least 299 chicken/alginate particles inoculated with Clostridium sporogenes spores per run. These tests showed the absence of viable microorganisms at the target treatment and positive growth when temperatures were below target, thereby verifying model predictions.
    Journal of Food Engineering. 10/2013; 118(3):312–325.
  • Jennifer J Perry, Ahmed E Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: Infection of laying hens with Salmonella enterica serovar Enteritidis leads to deposition of the pathogen into the albumen or yolk of forming eggs. Heat treatment can inactivate internalized Salmonella Enteritidis in shell eggs, but factors such as the nature and location of contamination may influence the efficacy of thermal treatments. In the current research, natural contamination was mimicked by introducing small inocula of Salmonella Enteritidis into different locations of shell eggs and incubating inoculated eggs. These pathogen-containing eggs were heated at 57°C for 40 min, and temperature within eggs was monitored at the locations of inocula. Comparison of inactivation at equivalent internal temperatures revealed similar levels of lethality regardless of inoculum location. Refrigeration between incubation and heat treatment did not increase thermal resistance of cells in albumen but decreased cell inactivation in yolk. Sequential application of heat and gaseous ozone allows for the development of a process capable of decontaminating shell eggs with minimal thermal treatment and impact on egg quality. Inoculated eggs were subjected to (i) an immersion heating process similar to that used in commercial pasteurization or (ii) immersion heating, at reduced duration, followed by vacuum (50.8 kPa) and treatment with ozone gas (maximum 160 g/m(3)) under pressure (∼187.5 kPa). All treatments tested produced greater than 5-log inactivation, which is required for "pasteurization" processes. Differences were observed in the visual quality of eggs depending on treatment parameters. Application of ozone subsequent to heating allows for a significant reduction in heating time without decreasing process lethality.
    Journal of food protection 02/2013; 76(2):213-9. · 1.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Use of bacteriocins in food preservation has received great attention in recent years. The goal of this study is to characterize enterocin RM6 from Enterococcus faecalis OSY-RM6 and investigate its efficacy against Listeria monocytogenes in cottage cheese. Enterocin RM6 was purified from E. faecalis culture supernatant using ion exchange column, multiple C18-silica cartridges, followed by reverse-phase high-performance liquid chromatography. The molecular weight of enterocin RM6 is 7145.0823 as determined by mass spectrometry (MS). Tandem mass spectrometry (MS/MS) analysis revealed that enterocin RM6 is a 70-residue cyclic peptide with a head-to-tail linkage between methionine and tryptophan residues. The peptide sequence of enterocin RM6 was further confirmed by sequencing the structural gene of the peptide. Enterocin RM6 is active against Gram-positive bacteria, including L. monocytogenes, Bacillus cereus, and methicillin-resistant Staphylococcus aureus (MRSA). Enterocin RM6 (final concentration in cottage cheese, 80 AU/mL) caused a 4-log reduction in population of L. monocytogenes inoculated in cottage cheese within 30 min of treatment. Therefore, enterocin RM6 has potential applications as a potent antimicrobial peptide against foodborne pathogens in food.
    BioMed research international. 01/2013; 2013:206917.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Intracellular free iron of Escherichia coli was determined by whole-cell electron paramagnetic resonance spectrometry. Ultrahigh pressure (UHP) increased both intracellular free iron and cell lethality in a pressure-dose-dependent manner. Iron chelator, 2,2'-dipyridyl, protected cells against UHP treatments. A mutation that produced iron overload condition sensitized E. coli to UHP treatment.
    Applied and Environmental Microbiology 11/2012; · 3.95 Impact Factor
  • Source
    En Huang, Yaoqi Guo, Ahmed E Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: A strain of Paenibacillus sp., OSY-SE, was isolated from soil and found to produce a novel lipopeptide antibiotic. The antibiotic, paenibacterin, is active against Gram-negative and Gram-positive bacterial pathogens. Paenibacterin is biosynthesized by a nonribosomal peptide synthetase pathway. Here we report the draft genome sequence of Paenibacillus sp. OSY-SE.
    Journal of bacteriology 11/2012; 194(22):6306. · 3.94 Impact Factor
  • Source
    En Huang, Ahmed E Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: Paenibacillus polymyxa OSY-DF is a Gram-positive rod-shaped bacterium isolated from a fermented vegetable food. This bacterial strain displays potent antimicrobial activities against Gram-positive and Gram-negative pathogenic bacteria, attributed to the production of the lantibiotic paenibacillin and the colistin peptide polymyxin E1. Here we report the draft genome sequence of Paenibacillus polymyxa OSY-DF.
    Journal of bacteriology 09/2012; 194(17):4739-40. · 3.94 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Probiotic lactic acid bacteria (LAB) have been shown to alleviate inflammation, enhance the immunogenicity of rotavirus vaccines, or reduce the severity of rotavirus diarrhoea. Although the mechanisms are not clear, the differential Th1/Th2/Th3-driving capacities and modulating effects on cytokine production of different LAB strains may be the key. Our goal was to delineate the influence of combining two probiotic strains of Lactobacillus acidophilus and Lactobacillus reuteri on the development of cytokine responses in neonatal gnotobiotic pigs infected with human rotavirus (HRV). We demonstrated that HRV alone, or HRV plus LAB, but not LAB alone, initiated serum cytokine responses, as indicated by significantly higher concentrations of IFN-α, IFN-γ, IL-12, and IL-10 at postinoculation day (PID) 2 in the HRV only and LAB+HRV+ pigs compared to LAB only and LAB-HRV- pigs. Peak cytokine responses coincided with the peak of HRV replication. LAB further enhanced the Th1 and Th2 cytokine responses to HRV infection as indicated by significantly higher concentrations of IL-12, IFN-γ, IL-4 and IL-10 in the LAB+HRV+ pigs compared to the LAB-HRV+ pigs. The LAB+HRV+ pigs maintained relatively constant concentrations of TGF-β compared to the HRV only group which had a significant increase at PID 2 and decrease at PID 7, suggesting a regulatory role of LAB in maintaining gut homeostasis. At PID 28, cytokine secreting cell (CSC) responses, measured by ELISpot, showed increased Th1 (IL-12, IFN-γ) CSC numbers in the LAB+HRV+ and LAB-HRV+ groups compared to LAB only and LAB-HRV- pigs, with significantly increased IL-12 CSCs in spleen and PBMCs and IFN-γ CSCs in spleen of the LAB+HRV+ group. Thus, HRV infection alone, but not LAB alone was effective in inducing cytokine responses but LAB significantly enhanced both Th1 and Th2 cytokines in HRV-infected pigs. LAB may also help to maintain immunological homeostasis during HRV infection by regulating TGF-β production.
    Beneficial Microbes 03/2012; 3(1):33-42. · 1.47 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This research was initiated to search for novel antimicrobial compounds produced by food or environmental microorganisms. A new bacterial strain, designated OSY-SE, which produces a unique and potent antimicrobial agent was isolated from soil. The isolate was identified as a Paenibacillus sp. through cultural, biochemical, and genetic analyses. An antimicrobial compound was extracted from Paenibacillus OSY-SE with acetonitrile and purified using liquid chromatography. After analyses by mass spectrometry (MS) and nuclear magnetic resonance (NMR), the antimicrobial compound was determined to be a cyclic lipopeptide consisting of a C(15) fatty acyl (FA) chain and 13 amino acids. The deduced sequence is FA-Orn-Val-Thr-Orn-Ser-Val-Lys-Ser-Ile-Pro-Val-Lys-Ile. The carboxyl-terminal Ile is connected to Thr by ester linkage. The new compound, designated paenibacterin, showed antagonistic activities against most Gram-positive and Gram-negative bacteria tested, including Listeria monocytogenes, methicillin-resistant Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella enterica serovar Typhimurium. Paenibacterin is resistant to trypsin, lipase, α-glucosidase, and lysozyme. Its antimicrobial activity was lost after digestion by pronase and polymyxin acylase. Paenibacterin is readily soluble in water and fairly stable to exposure to heat and a wide range of pH values. The new isolate and its antimicrobial agent are being investigated for usefulness in food and medical applications.
    Applied and Environmental Microbiology 02/2012; 78(9):3156-65. · 3.95 Impact Factor
  • Jennifer J Perry, Ahmed E Yousef
    [Show abstract] [Hide abstract]
    ABSTRACT: The issue of egg contamination with Salmonella enterica serovar Enteritidis rose to prominence several decades ago with increasing rate of infection around the world. Recent outbreaks have assured that this problem maintains a place in the public consciousness. Extensive research has been conducted to investigate the factors precipitating contamination events, their avoidance, and mitigation of the threat of contaminated eggs; consequently, regulations have been put in place to increase the safety of shell eggs. Despite these measures, rate of illness remains significantly higher than projected goals. This chapter includes information regarding the contraction of Salmonella species by laying hens and the subsequent deposition of these cells in shell eggs. Particular attention will be given to the prevalence of Salmonella Enteritidis in eggs and egg-containing products relative to other salmonellae. Research has been conducted to elucidate the mechanisms behind the fitness of Salmonella Enteritidis strains for this environment, but a consensus has yet to be reached. Novel methods of sanitizing shell eggs also are reviewed.
    Advances in applied microbiology 01/2012; 81:243-74. · 4.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Until recently, ohmic heating was commonly thought to kill microorganisms through a thermal effect. However a growing body of evidence suggests that non-thermal effects may occur. Our aim was to determine the kinetics of inactivation of Geobacillus stearothermophilus spores (ATCC 7953) under ohmic and conventional heating using a specially constructed test chamber with capillary sized cells to eliminate potential sources of error and ensure that identical thermal histories were experienced both by conventionally and ohmically heated samples. Ohmic treatments at frequencies of 60 Hz and 10 kHz were compared with conventional heating at 121, 125 and 130 °C for four different holding times. Both ohmic treatments showed a general trend of accelerated spore inactivation. It is hypothesized that vibration of polar dipicolinic acid molecules (DPA) and spore proteins to electric fields at high temperature conditions may result in the accelerated inactivation.
    Journal of Food Engineering 01/2012; 108(1):69–76. · 2.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the mode of action of gamma (γ) radiation, pulsed electric field (PEF) and ultra‐high pressure (UHP) against targeted pathogens should help improve implementation of these technologies. Listeria monocytogenes Scott A was treated with γ radiation, PEF and UHP at doses that caused equal lethality (3‐log inactivation). These doses were 0.57 kGy at 5C (γ radiation), 30 kV/cm at 22C for 216 µs (PEF) and 400 MPa at 24 ± 1C for 6 min (UHP). When structural changes in cells of L. monocytogenes were compared using transmission electron microscopy (TEM), the nucleoid region of γ ‐irradiated cells appeared to have spread throughout the cytoplasm. UHP‐treated cells showed aggregated cytoplasm, indicating extensive protein denaturing. Structural differences between PEF‐treated and untreated cells were minimal, as revealed by TEM. Electrophoresis of genomic DNA from γ‐irradiated L. monocytogenes showed considerable fragmentation. These DNA lesions were not detected when L. monocytogenes was treated with PEF or UHP. When irradiated cells were analyzed by pulsed field gel electrophoresis, the banding pattern changed into smearing. In conclusion, γ radiation, PEF and UHP targeted different loci in the cell, and thus synergy between these treatments against L. monocytogenes is likely. PRACTICAL APPLICATIONSRecently, there is an increase in the use of gamma (γ) radiation and ultra‐high pressure (UHP) in food processing as alternatives to heat. Other promising technologies, such as pulsed electric field (PEF), are in the experimental stage. This is a side‐by‐side investigation of γ radiation, UHP and PEF that helps in understanding the mechanism of bacterial inactivation by these technologies. The study could also help food processors in determining the suitability of these technologies for particular applications.
    Journal of Food Safety 01/2012; 32(1). · 0.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ultrahigh pressure (UHP) and pulsed electric field (PEF) are emerging processing technologies developed to enhance the safety while maintaining the fresh-like quality of food. For each food and process combination, a pathogen of concern (i.e., target pathogen) must be determined, and a low-risk microorganism that serves as the pathogen surrogate for process validation must be identified. The objective of this study was to identify a surrogate for Listeria monocytogenes for UHP and PEF process validation. Potential surrogates tested include four Lactobacillus spp., a Pediococcus sp., and a Listeria innocua strain. These were compared with nine L. monocytogenes strains, with regard to sensitivity to UHP and PEF processing. For UHP treatment, the strains were suspended in citrate-phosphate buffer (pH 7.0 or 4.5), sweet whey, or acidified whey and pressure processed at 500 MPa for 1 min. For PEF treatment, the strains were suspended in NaCl solution, acid whey, or sweet whey and processed at 25 kV/cm. The lethality of UHP or PEF treatment varied considerably, depending on medium types and pH and the treated strain. Treating the tested microorganisms with UHP inactivated 0.3 to 6.9 log CFU/ml for L. monocytogenes strains and 0.0 to 4.7 log CFU/ml for the potential surrogates. When PEF was employed, populations of tested microorganisms decreased < 1.0 to 5.3 log CFU/ml. L. monocytogenes V7 and OSY-8578 were among the most resistant strains to UHP and PEF treatments, and thus are candidate target strains. Lactobacillus plantarum ATCC 8014 demonstrated similar or greater resistance compared with the target organisms; therefore, the bacterium is proposed as a surrogate of L. monocytogenes for both processes under the conditions specified in the food matrices tested in this study.
    Journal of food protection 10/2011; 74(10):1655-61. · 1.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The physical quality and functionality of shell eggs, pasteurized with heat or a combination of heat and ozone, were assessed during eight weeks of storage at 4 or 25 °C. Shell eggs were treated as follows: (1) immersion heating that mimics commercial pasteurization processes (egg internal temperature of 56 ± 0.1 °C for 32 min), or (2) a newly developed combination process comprised of heating (56 ± 0.1 °C, internal, for 10 min) followed by gaseous ozone treatment. Eggs were tested for yolk index, Haugh units, albumen pH, albumen turbidity, and percent overrun. Additionally, albumen samples were assayed for lysozyme activity and free sulfhydryl group content, and were analyzed using differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy. Both processed and unprocessed eggs maintained superior quality when stored at 4 °C, as opposed to 25 °C. Pasteurization, regardless of method, led to superior maintenance of Haugh units during storage but also increased albumen opacity and decreased albumen overrun. Detrimental effects on quality markers were more severe in heat-pasteurized eggs than those treated with the ozone-based process. Pasteurization of shell eggs by either process did not affect lysozyme activity or sulfhydryl group content. Changes in protein secondary structure, as indicated by FTIR analysis, suggest that the ozone-based process is less damaging to albumen proteins than is the heat-alone process. In conclusion, heat-ozone pasteurization, by virtue of its less severe heat treatment, yields a safe final product that more closely resembles untreated shell eggs.
    Journal of Food Science 08/2011; 76(7):S437-44. · 1.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: γδ T cell responses are induced by various viral and bacterial infections. Different γδ T cells contribute to activation and regulation of the inflammatory response and to epithelial repair. How γδ T cells respond to rotavirus infection and how the colonization of probiotics influences the γδ T cell response were unknown. In this study, we evaluated by multicolor flow cytometry the frequencies and distribution of total γδ T cells and three major subsets (CD2-CD8-, CD2+CD8- and CD2+CD8+) in ileum, spleen and blood of gnotobiotic (Gn) pigs at early (3-5 days) and late phases (28 days) after rotavirus infection. The Gn pigs were inoculated with the virulent human rotavirus Wa strain and colonized with a mixture of two strains of probiotics Lactobacillus acidophilus and Lactobacillus reuteri. In naïve pigs, the highest frequency of total γδ T cells was found in blood, followed by spleen and ileum at the early age (8-10 days old) whereas in older pigs (32 days of age) the highest frequency of total γδ T cells was found in ileum and spleen followed by blood. Rotavirus infection significantly increased frequencies of intestinal total γδ T cells and the putatively regulatory CD2+CD8+ γδ T cell subset and decreased frequencies of the putatively proinflammatory CD8- subsets in ileum, spleen and blood at post-infection days (PID) 3 or 5. The three γδ T cell subsets distributed and responded differently after rotavirus infection and/or lactobacilli colonization. The CD2+CD8+ subset contributed the most to the expansion of total γδ T cells after rotavirus infection in ileum because more than 77% of the total γδ T cells there were CD2+CD8+ cells. There was an additive effect between lactobacilli and rotavirus in inducing total γδ T cell expansion in ileum at PID 5. The overall effect of lactobacilli colonization versus rotavirus infection on frequencies of the CD2+CD8+ γδ T cell subset in ileum was similar; however, rotavirus-infected pigs maintained significantly higher frequencies of CD8- subsets in ileum than lactobacilli-colonized pigs. The dynamic γδ T cell responses suggest that γδ T cell subsets may play important roles in different stages of immune responses after rotavirus infection and probiotic colonization. The knowledge on the kinetics and distribution patterns of γδ T cell subsets in naïve pigs and after rotavirus infection or lactobacilli colonization provides the foundation for further mechanistic studies of their functions.
    Veterinary Immunology and Immunopathology 06/2011; 141(3-4):267-75. · 1.88 Impact Factor

Publication Stats

2k Citations
211.67 Total Impact Points

Institutions

  • 1997–2014
    • The Ohio State University
      • Department of Food Science and Technology
      Columbus, Ohio, United States
  • 2013
    • Kasetsart University
      • Department of Food Science and Technology
      Krung Thep, Bangkok, Thailand
  • 2011
    • Cairo University
      • Faculty of Veterinary Medicine
      Cairo, Muhafazat al Qahirah, Egypt
  • 2008–2011
    • Virginia Polytechnic Institute and State University
      • Department of Biomedical Sciences and Pathobiology
      Blacksburg, VA, United States
    • Kocaeli University
      Cocaeli, Kocaeli, Turkey
  • 2010
    • Inha University
      • Department of Food and Nutrition
      Seoul, Seoul, South Korea
    • Universitat Rovira i Virgili
      • Departamento de Ingeniería Química
      Tarragona, Catalonia, Spain
  • 2006–2008
    • University of Wisconsin–Madison
      • Department of Food Science
      Madison, Wisconsin, United States