Campylobacter jejuni and Campylobacter coli are major bacterial food-borne pathogens that cause enteric diseases worldwide, resulting in significant public health and economic burden. These two closely related species colonize a wide range of farm animals including turkeys, pigs, chickens, and cattle. Consumption of meat (especially poultry) contaminated with C. jejuni or C. coli has been implicated as the major route of infection. When needed, antibiotics used for treatment are fluoroquinolones or macrolides such as erythromycin. Recent studies have shown that the percentage of C. coli that have resistance to antimicrobials, including those typically used for treatment of human campylobacteriosis, has increased, making it a top priority to investigate the mechanisms for acquisition and dissemination of antimicrobial resistance in these pathogens. Certain Campylobacter strains harbor a transcribed intervening sequence (IVS) in their 23S rRNA genes. Following transcription, the IVS is excised, leading to fragmentation of the 23S rRNA. The origin and possible functions of the IVS are unknown. Furthermore, the distribution of IVS-harboring strains within Campylobacter populations is poorly understood. In this study, strains of Campylobacter coli from turkeys, representing numerous different multilocus sequence typing (MLST)-based sequence types (STs), were characterized in terms of IVS content and erythromycin susceptibility. We identified strains that harbored IVSs in all three 23S rRNA genes, as well as strains lacked IVSs from at least one of the genes. The STs of the latter strains belonged to an unusual cluster of C. coli STs (?cluster II?), earlier found primarily in turkey strains, and characterized by presence of the C. jejuni aspA103 allele. The majority of strains harboring IVSs in all three 23S rRNA genes were resistant to erythromycin. In contrast, cluster II strains, which harbored at least one IVS-free 23rRNA gene, were susceptible to the antibiotic. Cluster II strains could be transformed to erythromycin resistance with genomic DNA from C. coli that harbored IVS and the A2075G transition in the 23S rRNA gene, associated with resistance to erythromycin in Campylobacter. Erythromycin-resistant transformants harbored both the A2075 transition and IVS. The findings suggest that absence of IVS in C. coli from turkeys is characteristic of a unique clonal group of erythromycin-susceptible strains, and that IVS can be acquired by these strains via natural transformation to erythromycin resistance. Analysis of C. coli and C. jejuni strains isolated from broilers, turkeys and swine has shown the association of the lack of IVS and erythromycin susceptibility is unique to C. coli from turkeys. The presence of the C. jejuni aspA103 allele in the chromosome of cluster II C. coli strains is a unique characteristic of this clonal group. To further characterize the genome composition in the aspA region in cluster II strains, we determined the corresponding DNA sequences from two turkey-derived cluster II C. coli strains (6979 and 7474, of ST-1150 and ST-1161, respectively). Genomic organization upstream of the aspA gene was divergent between these two cluster II strains and the reference strain C. coli RM2228, the genome sequence of which has been completed. Genes encoding a putative Crp-family transcriptional regulator (CCO0137) and a conserved hypothetical protein (CCO0138) that were present in C. coli RM2228 and C. coli 6818 were not found in the same genomic region in C. coli 6979 or C. coli 7474. Moreover, single nucleotide polymorphism (SNP) analysis revealed that genes encoding subunit II of cytochrome d ubiquinol oxidase (cydB) and a putative aspartate racemase (CJ0085c) harbored numerous C. jejuni-specific SNPs. Interestingly, genes encoding subunit I of cytochrome d ubiquinol oxidase (cydA) and uracil-DNA glycosylase (ung) harbored C. coli-specific SNPs in their 5? portions but C. jejuni-specific SNPs in their 3? portions, suggesting that these may be hybrid genes that were originated from C. jejuni and C. coli. Our data suggest the presence of recombination events in the genomic region between cydA and ung in cluster II strains of C. coli. Such genomic features may contribute to the observed prevalence of cluster II strains among C. coli from turkeys, and to the characteristic susceptibility to erythromycin exhibited by these strains.

Listeria monocytogenes, Salmonella and Campylobacter combined are responsible for the majority of foodborne disease hospitalizations and over 1200 deaths annually in the U.S. alone. Although raw poultry has been identified as a source of these pathogens, most microbiological studies have focused on broilers with little attention given to turkey processing. The purpose of this research was to investigate the prevalence of select pathogens (L. monocytogenes, Salmonella spp., and Campylobacter spp.) and microbiological indicators (Enterococcus spp.) in the turkey processing environment. Environmental samples were collected in one Southeastern processing facility using swab methods at two month intervals over a period of 14 months. Samples were taken from conveyors, drains, walls and various food contact surfaces. Isolation and identification of bacteria was done using the USDA-FSIS Microbiology Laboratory Guidebook protocols. The prevalence of contamination was 11.5%, 7.4%, and 0.4% for L. monocytogenes, Salmonella, and Campylobacter, respectively. Enterococcus spp., an environmental indicator of fecal contamination, were isolated from over >75% of the samples screened. Salmonella isolates were typed using pulsed-field gel electrophoresis (PFGE) and Enterococcus isolates were speciated by PCR with antibiotic resistance profiles characterized using the SensiTitre system. A diverse set of relatively non-persistent Salmonella strains were obtained from the processing environment, as evaluated by PFGE. Thirty-nine percent of the Enterococcus isolates were speciated as E. faecium and 55% were E. faecalis. Both E. faecalis as E. faecium strains were susceptible to most antibiotics of human clinical relevance. Thirty-three L. monocytogenes strains were screened for their biofilm formation capabilities using a microtiter well assay. None of the strains formed a biofilm in monoculture; however, sixteen of the strains were able to form a biofilm in the presence of another organism. Data collected in prevalence studies such as this one can help processors identify contamination frequency and sites in an effort to control resident pathogenic bacteria in the processing environment.

The objective of this research was to quantitatively describe the the denaturation and aggregation processes of a-lactalbumin at neutral pH in order to understand their interrelationship and effect on solution stability. Three different preparations of a-La had similar denaturation temperatures, enthalpies and % reversibility as measured by differential scanning calorimetry. However, Native PAGE reveled three non-native monomer bands that corresponded to three distinct dimer bands indicating specific intramolecular disulfide bond shuffling leads to formation of disulfide-specific dimers. The apo protein was the most thermostable to turbidity development. The Ca-La was the most thermostable holo- preparation. Turbidity development at 95 degreesC (95 degrees C) indicated pure preparations intensely associate through hydrophobic interactions through bridging by divalent phosphate and this effect was mitigated by decreasing the ionic strength, decreasing the phosphate charge to ¡V1 (at pH 6.6) or decreasing the temperature. The aggregation behavior of a commercial a-La was investigated at neutral pH and 95?aC in a complex mineral salt environment to understand general stability factors involved in a nutritional beverage. The objective was to understand the effect of a-La lot variation, relative b-lactoglobulin concentration and excess calcium on the aggregate size development as measured by light scattering and turbidity development. The lot of holo-a-La possessing a higher intrinsic b-Lg concentration had higher solubility at pH 6.80, evolved more reactive thiol groups, had a 25% faster first order rate constant, dissociated only slightly with cooling and formed spherical aggregates with a much higher molecular weight. Aggregates intrinsic to the protein powder may play a role in aggregate growth and shape. Adding increasing quantities of b-Lg generally decreased solubility. The highest b-Lg concentrations investigated demonstrated a net thiol oxidation and, subsequently, had a diminished ability to aggregate through hydrophobic interactions. Adding excess calcium caused a dramatic loss of solubility at pH 7.0 and required an increase in pH to 7.5 to regain solubility.

Studies have demonstrated the cardiovascular protective properties of peanuts and peanut oil through the reduction of low density lipoprotein cholesterol (LDL-C) while maintaining healthy levels of high density lipoprotein cholesterol (HDL-C). The cardiovascular protective effects of fat free peanut flour have never been evaluated despite the fact flour contains arginine, flavonoids, folates and other compounds beneficial to cardiovascular health. In addition, there is a growing body of evidence suggesting unsaturated fatty acids and arginine may promote bone strength. The objective of this study was to evaluate the effects of fat free peanut flour and other peanut components on plasma cholesterol risk factors for cardiovascular disease, atherosclerosis and bone strength in male Syrian golden hamsters. Seventy-six hamsters were randomly divided into four groups and each group was fed a different isocaloric diet for twenty-four weeks. Each experimental diet was a modification of the high fat and high cholesterol control diet. Modifications to the control diet were made by substituting fat free peanut flour (<0.5% oil), peanut oil or whole peanuts for similar metabolic components. Randomly selected hamsters from each diet group were euthanized at 0, 12, 18 and 24 weeks at which point blood plasma, aortas and femurs were collected. Plasma was analyzed for total plasma cholesterol (TPC) and lipoprotein distribution by high-performance gel chromatography. Aortic total cholesterol (TC), free cholesterol (FC) and cholesteryl ester (CE), a metabolic atherosclerosis indicator, were determined as mg/g protein. Hamsters consuming diets containing fat free peanut flour, peanut oil or whole peanuts had significantly lower TPC and LDL-C than the control group. There were no significant differences in HDL-C among any of the diet groups. Aortic TC, FC and CE were significantly lower in the fat free flour, peanut oil and peanut diet group hamsters compared to those in the control group. Results indicated peanuts, peanut oil and fat free peanut flour in diets reduced blood chemistry risk factors and slowed the development of atherosclerosis, as indicated by low levels of CE, in male Syrian golden hamsters fed a high fat and high cholesterol diet. The results for bone strength were variable and overall the effects of fat free peanut flour, peanut oil and whole peanuts on bone strength were inconclusive.

Peanuts are a valuable agricultural commodity and roasted peanut flavor is the driving force for consumer purchase and consumption. The development of off-flavors is a major concern to the peanut industry and physiological differences (i.e. oil and sugar content) among the different maturity classes can influence the presence and/or absence of specific flavors. Fruity fermented (FF) is a common off-flavor found in peanuts and is developed when peanuts are cured at excessive temperatures (>35ºC). Previous literature has characterized FF off-flavor using descriptive sensory analysis; however, there is little information on FF off-flavor using consumer evaluation. The peanut plant has an indeterminate flowering pattern meaning a range of maturities are present at harvest and the immature and mature peanuts differ in roasting and flavor quality. Immature peanuts tend to have more FF off-flavor than mature peanuts which results in a FF distribution within large peanut lots. The flowering pattern and heterogeneous distribution of immature and mature seed make it challenging to obtain an accurate determination of FF off-flavor in a bulk lot. Establishing links between flavor and volatile flavor compounds can be obtained by using sensory and instrumental analyses. Currently, there is little research published on the volatile components that contribute to naturally occurring FF off-flavor. The objectives of this research were to: i) characterize consumer?s perception of FF off-flavor, ii) measure the variability and determine the FF distribution in bulk lots, iii) and identify the volatile compounds responsible for naturally occurring FF off-flavor using sensory and instrumental analyses. Descriptive sensory analysis was conducted to determine the no FF and FF samples used for the consumer study. Two-hundred and eight consumers evaluated a control (no FF off-flavor), low (1.0 FF) intensity, and a high (3.0 FF) intensity using two different scaling techniques: category and line scales. Results indicated FF off-flavor negatively impacts consumer acceptance of peanuts and the line scales were more sensitive and showed more differences among the samples compared to the category scale. The second study investigated the distribution of FF off-flavor in peanut lots and the results indicated that FF intensity varied from lot to lot and within a single bulk lot. Solvent assisted flavor evaporation (SAFE), solidphase microextraction (SPME), gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), and model systems were conducted to identify the compounds responsible for naturally occurring FF off-flavor. Volatile analysis indicated that ethanol and the esters previously reported as causing FF off-flavor were not detected in natural FF samples by solvent extractions; however, they were present in natural and artificially created Georgia Green and Flavor Runner 458 samples by headspace extractions. These findings emphasizes that the use of laboratory created samples should not be used to identify off-flavor sources in peanuts. Additionally, the use of analytical techniques to identify FF off-flavor in bulk lots cannot be achieved using ethanol or esters as indicators.

The use of microwave technology as an alternative blanching method for peanuts could potentially reduce energy costs and processing time, and lead to products with better nutrient retention. However, an off-flavor was found in peanuts which were microwave-blanched at high temperatures. As a result, the objective of this research has been to determine the impact of different microwave blanching parameters on the properties of roasted peanuts, and to characterize the off-flavor observed during high-temperature microwave blanching using a descriptive sensory panel and analysis of volatile flavor compounds. The processing parameters best suited for microwave blanching of peanuts were determined based on energy absorbed during processing, internal and surface temperatures, loss in moisture content, and blanchability. The best blanchability resulted from higher process temperatures and lower final moisture content. However, peanuts which reached the highest internal temperatures during blanching also developed an off-flavor, which was characterized by increased intensities of stale/floral and burnt/ashy notes. Solvent extraction / solvent assisted flavor evaporation (SAFE), gas chromatography-olfactometry (GC/O), gas chromatography-mass spectrometry (GC/MS), aroma extract dilution analysis (AEDA), threshold testing, and model systems were used to examine the chemical compounds which may be responsible for this microwave-related off-flavor. Analysis revealed an increased formation of guaiacol, phenylacetaldehyde, and 2,6-dimethylpyrazine in the off-flavored peanuts as compared to a process control, which led to the burnt and stale/floral characteristics noted by descriptive sensory panel. These compounds were only a small fraction of over 200 aroma-active compounds which were found to contribute to roasted peanut flavor using GC/O. This research illustrates the importance of the relative concentrations of the many aroma-active compounds found in peanuts. These findings could aid in training sensory panels to evaluate processing-related off-flavors, because guaiacol and phenylacetaldehyde could be used as chemical standards to define the burnt/ashy and stale/floral off-flavors which can occur during high temperature processing. Through this project, it was determined that it is possible to achieve acceptable blanchability in peanuts using microwave blanching while minimizing the possibility of an off-flavor.

Storing fresh cucumbers for an 8 to 12 week period in an acidified, non-fermented environment prior to processing would extend the time for processing locally grown cucumbers into pasteurized pickle products. The effect of acidified storage of fresh cucumbers for up to 120 days prior to their conversion to pasteurized dill pickles was evaluated. Cucumbers stored at 18ºC prior to pasteurization maintained a fresh, non-cured appearance as well as a firm texture. Equilibrated acid concentrations of 3.5% acetic acid also helped to reduce the amount of curing and maintained firmness in cucumber tissue. Dill pickles made from acidified, bulk stored cucumbers maintained a firm texture after pasteurization. However, the cured appearance of bulk stored cucumbers increased by 40% within 30 days of pasteurization so that it was much higher than the cured appearance of dill pickles made directly from the same lot of fresh cucumbers and stored for an equivalent period of time after pasteurization. Sour, sweet, bitter and vinegar intensities were similar for dill pickles prepared from either bulk stored or fresh cucumbers. Firmness, saltiness, and dill flavor while significantly different, differed by less than 1 point on a 15-point scale. The major flavor difference between pasteurized dill pickles made from stored acidified cucumbers and pickles made directly from fresh cucumbers is that pickles made from stored cucumbers had an âotherâ flavor. The intensity of this flavor was perceived at a similar level regardless of the brine composition or storage time of the cucumbers prior to pasteurization. Descriptors for this âotherâ flavor were chlorine, pool, barny and metallic. GCxGC-TOFMS analysis of volatile components in dill pickles prepared from bulk stored cucumbers and dill pickles prepared from fresh cucumbers resulted in detection of 24 components that were significantly different (p<0.05) between at least one treatment pair. Individual volatile components did not provide a clear basis for differentiation among different storage brine treatments. However, PCA analysis using the 24 components was able to differentiate treatments.

Residence time distributions of multiple particles (as affected by process and system parameters) were investigated during non-Newtonian tube flow. Process parameters included flow rate, particle type, carrier fluid viscosity, and particle concentration. The system parameter of interest was the holding tube configuration. Polystyrene and acrylic particles were used as model food particles. Digital imaging analysis was used to obtain residence time data of particles. A novel type of holding tube (chaotic holding tube) was constructed. Comparisons among the straight, single helical, double helical, and chaotic holding tube were performed in terms residence time distribution (RTD) of particles. In addition, the effect of inclination angle (0 º and 45 º) of the chaotic holding tube was investigated. It was found that the narrowest RTD of particles was obtained in the single helical holding tube. RTstd in the chaotic holding tube was greater than that in the single helical holding tube, but lower than those in the straight and double helical holding tubes. The most significant process parameter affecting RTD was flow rate. The effect of flow rate was more pronounced for high density (acrylic) particles. Carrier fluid viscosity, particle type, and particle concentration did not have significant effects on the overall RTstd. Trends observed in the chaotic holding tube were similar to those observed in the single helical holding tube. However, there were some cases where use of chaotic holding tube resulted in narrower RTD of particles. Changing the inclination angle from 0 º to 45 º in the chaotic holding tube resulted in wider RTD of both types of particles.

Outbreaks of illness caused by acid-tolerant bacterial pathogens in acid foods have raised questions about the safety of acidified foods. However, acidified foods have an excellent safety record which is in part due to the presence of organic acids. The objective of this research was to (1) a develop method that allowed rapid comparison of test acids on E. coli, (2) measure the effectiveness of acetic, malic, citric, and lactic acids to kill Escherichia coli O157:H7 independent of pH effects and (3) examine the mechanism of protection of D-lactic acid and on E. coli O157:H7. Gluconic acid (20 mM), which has been shown to be non-inhibitory to E. coli, was used to buffer solutions with 0 mM to 420 mM fully protonated concentrations of the test acids at various pH?s and temperatures, with ionic strength adjusted to 0.60-0.68. The effect of anaerobic incubation during acid challenges was examined. We found that using the 96 well microplate and determining viability by plating before and after acid challenge was consistent reproducible and efficient method which allowed us to evaluate up to 96 solution simultaneously. Compared to pH, acetic, malic, pyruvate, and particularly D-lactic acids had a significant protective effect on E. coli O157:H7 at low (1?20 mM) protonated acid concentrations. Citric acid was not found to exhibit any protective effect at similar concentrations. At higher concentrations L-lactic acid was the most lethal acid followed by acetic, citric and malic acids which had about equal degree of lethality against the O157:H7 strains. To our knowledge this is the first time organic acids have been observed to have a protective effect on pathogenic bacteria. D-lactic acid and pyruvate protected cells against 40 mM protonated acetic acid which has previously shown to reduce cells beyond detection during the acid challenge. These acids may protect the cells by inactivation of reactive oxygen radical species. These results showed that oxygen may play a major role in the effect of organic acids on E. coli O157:H7. It is important to understand the mechanism of this protective effect to be able to assure safety of acid and acidified foods. Additional research will be needed to understand acid specific effects on the survival of E. coli O157:H7 and other acid-resistant food pathogens in acid and acidified foods. In order to reliably and efficiently eliminate acid tolerant pathogens from acid and acidified foods we should have a clear understanding of the environmental factors that affect killing of these microorganisms. Thus, the role of oxygen during acid challenge studies must be determined to assure the safety of acid and acidified products.

Dry yeast can be utilized in both ale and lager beer production to provide an inexpensive source of large amounts of viable cells for fermentation. This study examines the desiccation tolerance of different strains of S. pastorianus and the subsequent fermentation performance in comparison to S. cerevisiae. The use of active dry brewerâs yeast (ADY), Saccharomyces cerevisiae, as a starter for the production of ales has been gaining popularity within the brewing industry, spurring manufactures to also produce active dry lager yeast (ADLY), S. pastorianus. The drying process is known to have a greater negative effect on the cell viability and physiology of ADLY than that of ADY, possibly due to the fastidious growth, low production temperature and poor thermotolerance of S. pastorianus. This may result in lower cell viability and concentration of ADLY starter cultures, which could lead to stuck or slow fermentations. S. pastorianus is a hybrid organism resulting from a cross between S. cerevisiae and S. bayanus. It has been proposed that it can be categorized into two distinct groups: Group 1 (S. pastorianus- Saaz type) has lost a significant amount of the genomic content contained within S. cerevisiae and is therefore closer to S. bayanus; while Group 2 (S. pastorianus- Frohberg type) has retained almost all of the genomic content of S. cerevisiae. To investigate whether these two groups differ in their tolerance to desiccation, both groups of S. pastorianus were spray dried at 140oC and rehydrated in phosphate buffer at 25oC for 30 minutes. The viability of the rehydrated cultures was determined using microscopic and viable cell counts. The fermentation performance of the cultures was tested by inoculating equal counts of viable rehydrated cells into brewerâs wort and monitoring changes in cell count, carbohydrate and alcohol concentration until completion. The findings suggest that the S. pastorianus- Frohberg type is less tolerant to desiccation than either S. cerevisiae or S. pastorianus- Saaz type. The Frohberg type shows evidence of membrane damage which could delay the onset of fermentation. Utilization of the correct strain of ADLY could reduce the possibility of contamination or extended lag phases leading to stuck fermentations.