Browsing by Author "Lee-Ann Jaykus, Committee Member"

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Affinity Adsorption of Viruses Using Small Peptide Ligands
(2008-07-11) Heldt, Caryn L; Robert M. Kelly, Committee Member; Jan Genzer, Committee Member; Lee-Ann Jaykus, Committee Member; Orlando J. Rojas, Committee Member; Ruben G. Carbonell, Committee Chair
Analysis of Radiant Heating to Produce an Alternative Frying Process
(2004-11-20) Lloyd, Brian Jeffery; Brian Farkas, Committee Chair; Lee-Ann Jaykus, Committee Member; Kevin Keener, Committee Co-Chair; Andy Hale, Committee Co-Chair
Radiant emission from short, medium, and long wavelength thermal radiant emitter systems typically used for food processing applications were quantified. Measurements included heat flux intensity, emitter surface temperature, and spectral wavelength distribution. Heat flux measurements were found highly dependent on the incident angle and the distance from the emitter facing. The maximum flux measured was 5.4 W/cm2. Emitter surface temperature measurements showed that short wavelength radiant systems had the highest surface temperature and greatest thermal efficiency. The emitter spectral distributions showed that radiant emitter systems had large amounts of far infrared energy emission greater than 3 μm when compared to theoretical blackbody curves. The longer wavelength energy would likely cause increased surface heating for most high moisture content food materials. The effect of finish heating method: immersion frying, oven heating or dynamic radiant heating was evaluated for texture, color, and sensory properties of par-fried French fries. Peak breaking force was highest for radiant heated French fry samples. Color analysis revealed equivalent b-value (yellowness) of crust color for immersion fried and radiant heated French fries. Sensory evaluation indicated overall acceptability of radiant heated French fries equivalent to traditional immersion fried French fried potatoes. A numerical simulation of high intensity radiant heating was developed for a potato slab. The simulation predicted the temperature profile throughout in a one-dimensional slab during a radiant heating process. A surface crust and core region were defined and the increase in crust thickness was tracked. Measured surface and core temperatures showed excellent agreement with simulation results producing an average deviation of less than 3°C during a 15,000 and 27,000 W/m2 constant heat flux validation experiment. The simulation could be used as a tool to evaluate radiant heating of food products to simulate immersion frying and crust formation.
Factors affecting susceptibility to - and management of - postharvest soft rot of sweetpotatoes caused by Rhizopus stolonifer.
(2008-11-25) Edmunds, Brooke Aurora; James W. Moyer, Committee Member; D. Michael Benson, Committee Member; Gerald J. Holmes, Committee Chair; Lee-Ann Jaykus, Committee Member
Studies were undertaken to explore the relationship of R. stolonifer susceptibility with preharvest growing conditions and postharvest handling of sweetpotatoes. Additional studies were also completed to identify effective decay control products. A three-year study investigated the effect of preharvest conditions on R. stolonifer and Erwinia chrysanthemi susceptibility. Roots were harvested from 75 sweetpotato fields and information collected including soil samples, weather during the growing season, weed density, and insect injury (153 predictors). Roots were inoculated after 100 days in storage. Mean R. stolonifer incidence was 34.9% (standard deviation=31.7%) and mean E. chrysanthemi incidence was 51.0% (standard deviation=30.5%). Predictive models were developed using forward stepwise regression to identify predictors of interest, followed by mixed model analysis (p-value<0.05) to produce a final model. R. stolonifer susceptibility is best predicted by soil calcium (% CEC), plant-available soil phosphorus, soil humic matter (%), mean air temperature, mean volumetric soil moisture at 40 cm, and mean soil temperature at 2 cm (all over the growing season). E. chrysanthemi susceptibility is best predicted by soil pH and days that soil temperature exceeds 32 ÂºC (14 days pre- harvest). Studies were also conducted to define the relationship between postharvest handling and susceptibility to R. stolonifer. Experiments designed to simulate packingline handling found root ends are more susceptible that mid-sections and that increasing the number of time a root is dropped as well as increasing the impact force resulted in increased decay susceptibility. â€˜Hernandezâ€™ roots were significantly more susceptible than â€˜Beauregardâ€™ in all experiments. To confirm the relationship of impacts and disease development, Beauregard roots were sampled from locations along commercial packinglines. High decay in inoculated as compared to non-inoculated roots indicates that wounding is occurring that could result in disease if the pathogen was present at higher levels. Evaluations of reduced-risk fungicides, bio-fungicides and generally recognized as safe products for efficacy against R. stolonifer found that reduced-risk chemistries boscalid+pyraclostrobin and fludioxonil significantly reduced R. stolonifer development and performed similarly to dicloran. Pseudomonas syringae based products were moderately effective although results were extremely variable among tests. Generally recognized as safe treatments were ineffective by testing methods used.
Impact of Poultry Age, Season, Litter Quality, and Nutritional Intervention Strategies on Salmonella Prevalence and Populations, Serotypes, Genotypes, and Antibiotic Resistance Profiles
(2007-10-31) Santos, Fernanda Botaro de Oliveira; Brian W. Sheldon, Committee Chair; Donna K. Carver, Committee Member; Lee-Ann Jaykus, Committee Member; Peter R. Ferket, Committee Co-Chair
Poultry-related salmonellosis is an on-going problem that the poultry industry must continue to address. To address these challenges, Salmonella populations present on litter and fecal samples of brooder and grow-out turkey farms were assessed using a quantitative procedure. Furthermore, serotyping, genotyping by pulsed-field gel electrophoresis and antibiotic resistance-susceptibility analyses were used to investigate the diversity of the Salmonella serotypes present on these farms. Additionally, alternative on-farm pathogen intervention strategies including feeding whole or coarsely ground grains, increasing insoluble fiber content of the diet and use of an alternative non-litter cage-based housing design (Broilermatic System) were evaluated. Salmonella litter populations averaged 2 logs higher in 3-wk turkey samples compared to samples from 19-wk birds. Turkey age also influenced Salmonella serotypes, genotypes and antibiotic resistance profiles. Only serovars Javiana and Mbandaka were common between 3 and 19-wk old turkeys. A higher frequency of multidrug resistance was observed in Salmonella isolates recovered from samples of 3-wk birds, on average isolates were resistant to >4 antibiotics tested. Supplementing coarse ground corn and increased insoluble fiber (wood fiber) content into the turkey diet did not adversely impact body weights. However, the treatments did not influence Salmonella colonization or fecal shedding of turkeys. To examine the impact of housing design and addition of whole or coarsely ground grains on performance, intestinal microbial diversity and Salmonella colonization, broilers were reared on four diets consisting of finely or coarsely ground corn and finely ground or whole triticale to market age and Salmonella populations measured. Whole grain supplementation decreased Salmonella cecal populations while rearing broilers on litter floor as opposed to the Broilermatic System resulted in significant reductions in Salmonella cecal populations. Moreover, feeding whole triticale presumably encouraged the proliferation of bacterial populations which may have competitively excluded Salmonella in the ceca of broilers. In conclusion, highly variable Salmonella populations and serotypes were detected across all commercial turkey farms and the use of alternative feed ingredients such as triticale may help to reduce Salmonella colonization in poultry. Moreover, diet composition and grain coarseness as well as housing design can influence the diversity of the commensal intestinal microflora which may help in the control of Salmonella colonization in broiler intestines.
Impact of Temperature and pH on the Survival of Listeria monocytogenes in Souse meat
(2006-12-11) Kim, Mina K; Dr. Dana J. Hanson, Committee Co-Chair; Lee-Ann Jaykus, Committee Member; Dr. MaryAnne Drake, Committee Co-Chair
Souse meat is an acidified, gelled product made with pork co-products such as ears, hearts, and tongues. This fully cooked, ready-to-eat (RTE) product is popular in the southern United States, and represents a significant volume of processed meat sold in this region. There is a "zero-tolerance" policy for Listeria monocytogenes in RTE meat products. The growth⁄survival of L. monocytogenes in souse is unknown. The objective of this study was to determine the effectiveness of three different souse formulations in controlling the growth of L. monocytogenes at two different refrigerated storage temperatures. Three souse formulations (pH 4.3, 4.7, and 5.1) were produced in triplicate by a local processing plant. Products were subsequently surface-contaminated with a three-strain cocktail of L. monocytogenes. Uninoculated product served as the control. The initial contamination level was 105 cfu⁄cm2. Products were vacuum-sealed and stored at two different temperatures (5°C and 10°C). Microbial counts were monitored (total aerobic plate count and L. monocytogenes) twice weekly through 32 days storage. Data were analyzed by regression analysis and D values were compared using analysis of variance with means separation. Souse meat did not support the growth of L. monocytogenes, regardless of product formulation or storage temperature. D values for products with a pH of 4.7 or 5.1 were not different (40days at 5C, TSAYE; 27 days at pH 4.7, 21 days at pH 5.1 at 5C, TSAYE) (p>0.05). A lower product pH (4.3) decreased L. monocytogenes survival (D value = 9days) compared to higher pH products (p<0.05). D values for products stored at 5o C and 10o C did not differ (p>0.05). Consumer acceptability of pH 4.3 products was not different from (typical) pH 4.7 product (p>0.05). These results demonstrate that conventionally produced souse meat does not support the growth of L. monocytogenes and that inactivation of the organism is favored for products formulated at lower pH (<4.3).
Phenotypic and genetic characterization of Listeria monocytogenes from the environment of turkey processing plants
(2009-01-11) Mullapudi, Savitri; Jonathan C. Allen, Committee Member; Lee-Ann Jaykus, Committee Member; Sophia Kathariou, Committee Chair
Resistance of clinical strains of Listeria monocytogenes to heavy metals, especially cadmium and arsenic has been used extensively for subtyping. Furthermore, the three most recent multistate outbreaks of listeriosis in the United States (1998-99 hot dog outbreak, and outbreaks in 2001 and 2002) have involved cadmium resistant strains two of which (1998-99 and 2001) were resistant to the quaternary ammonium disinfectant benzalkonium chloride (BC) as well. In these outbreak strains, genes mediating cadmium and BC resistance were found to be localized in two different gene cassettes on large plasmids (ca. 80 kb). However, limited information has been available on resistance to cadmium, arsenic and BC among L. monocytogenes isolates from the food processing plant environment. It is not known whether resistance to heavy metals (cadmium and arsenic) and BC is plasmid-borne in such strains and whether resistance to cadmium and arsenic may be correlated to resistance to disinfectants commonly used in the processing plant environment. Furthermore, information regarding contamination patterns of turkey processing plants in the United States with regards to different serotypes and strain types of L. monocytogenes is currently inadequate. In this study, we characterized 123 L. monocytogenes isolates (53 of serotype 1/2a or 3a, 39 of serotype 1/2b or 3b, and 27 of the serotype 4b complex, consisting of serotype 4b and the closely related serotypes 4d and 4e, and 4 strains of serotype 1/2c or 3c) from the environment of six turkey processing plants in the United States for cadmium, arsenic and BC resistance. In addition, these isolates were subtyped using pulsed field gel electrophoresis (PFGE). Moreover we investigated the prevalence among these isolates of three different cadmium resistance cadA determinants identified to date in L. monocytogenes: cadA1 (associated with Tn5422), cadA2 (associated with plasmid pLM80, identified in the 1998-99 outbreak strain), and cadA3, associated with the integrated conjugative element (ICE) of L. monocytogenes EGD-e, respectively). We employed plasmid curing protocols to examine if the resistance to heavy metals (cadmium and arsenic) and to BC was plasmid-borne and to assess the stability of cadmium and BC resistance among isolates of L. monocytogenes from the processing plant environment. Resistance to cadmium and BC was more common in serogroup 1/2 strains than 4b, whereas arsenic resistance was more commonly encountered in strains from the serotype 4b complex. We found substantial strain diversity in the turkey processing plants with 104 distinct PFGE types from 123 isolates using both enzymes (AscI and ApaI), resulting in Simpsonâ€™s index of diversity (D) of 0.995. Plant-specific strains were commonly found within each serotype. Heavy metal (cadmium and arsenic) and BC resistance were detected frequently among the serogroup 1 /2 strains. Our investigation has shown that 28% of the L. monocytogenes strains harbored both cadA1 and cadA2 and that the type of determinant (cadA1 vs. cadA2) may vary based on serotype as well as based on BC resistance (cadA2 being found more frequently among BC resistant than BC susceptible strains of the same serotype). The results also showed that the curing of plasmid borne cadmium and BC resistance was possible in certain strains isolated from the environment of turkey processing plants although the rate of plasmid loss was low. These results suggest that the processing plant environment may represent a reservoir for L. monocytogenes having resistance to cadmium and BC. Further studies are needed to elucidate the mechanisms underlying the prevalence of the different determinants, and their possible role in the ecology and evolution of L. monocytogenes in the processing plant environment. In addition, further studies need to be undertaken to confirm the location of the resistance determinants on plasmids, or possibly on the chromosome, especially in strains that failed to lose resistance following exposure to plasmid curing protocols.