▼ Several coating applications in the food industry were studied. The applications studied included electrostatic atomization, browning enhancers, and electrostatic powder coating. Electrostatic atomization of food oils cannot be achieved without increasing the conductivity of the oil (<10-10µS/cm) into the atomizable range (~10-6-10-9µS/cm). Electrostatic atomization of water-soluble food additives and emulsions cannot be achieved using current atomization methods, limiting the utilization of the process in the food industry. This study sought to create a general atomization aid for oils, emulsions and water-soluble additives. The process restricted the surface-conductivity of water-containing solutions through the creation of a lycotropic liquid crystal phase using a saturation-based minimal-surfactant emulsification process (emulsifier content <0.01-0.001%). Charging of the oil was achieved by inducing increased dissociation of H2O molecules and subsequent migration of hydroxyl-groups to the interface. Color and texture development during the cooking of potato products is one of the main drivers of consumer acceptability. A comparison of color and texture development in raw and par-fried French fries and potato rounds processed by deep fat frying, microwaving and baking was performed. The effect of wood pyrolysis-derived carbonyls on color and texture development in potato products was also studied and compared to traditional dextrose-derived browning agents. A Browning agent (wood pyrolysis derived carbonyls), smoke flavor, sodium erythorbate (SE): ascorbic acid (AC) mixture, and sodium erythorbate alone were coated electrostatically and non-electrostatically onto frozen par-fried French fries, pepperoni slices, bologna slices, and mozzarella cheese slices respectively. Powder transfer efficiency and reproducibility, color development, reproducibility and evenness, mold inhibition and sensory preference were measured. Electrostatics leads to increased functionality over non-electrostatics in brown color generation, smoke-flavor preference, redness in meat and mold inhibition. Advisors/Committee Members: Barringer, Sherryl.

▼ Nylon 6 organoclay nanocomposites were prepared by melt processing using a twin screw extruder. Five different films were produced with five different % loadings (0, 2, 4, 6, and 8%). This study had three main objectives. The first was to investigate the effects of loading percentages on the barrier, thermal and mechanical properties of nylon 6 nanocomposite materials. The second was to study the effects of 0, 50 and 80% RH on the oxygen permeation of the nylon 6/nanocomposite films. The third was to investigate the properties of nylon 6 nanocomposite materials exposed to typical food processing conditions. These films were tested for their permeabilities to oxygen (OTR), carbon dioxide (CO2TR), and water vapor (WVTR). Thermal properties testing on the samples included differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Tensile strength at break, tensile modulus at break, and the percent elongation for the five films were examined using an INSTRON tester. Transmission electron microscopy (TEM) was used to investigate the morphology of the five films. Results showed that all gas barriers significantly increased with percent loading but there were no significant differences (P>0.05) between the 6 and 8% for the CO2TR. For the DMA, the storage modulus also significantly increased (P<0.05) with increasing loading except between the 2 and 4% concentrations. For the DSC analyses, enthalpy of fusion decreased slightly from an average of 39 J/g (control) to 32J/g (8% loading). The melt temperature also decreased from 227 to 222°C between those loadings. High pressure processed samples had the highest barrier against oxygen permeation when compared with the retorted and controls. Retorting seemed to reduce the tensile strength slightly; however, no significant changes in modulus and elongation occurred after retorting and HPP. These results showed that increasing percent loadings increased the stiffness of the material at the expense of its tensile strength. Samples with 8% loading, while showing better barrier in some cases, caused a mechanical weakening of the material not experienced at the 6% loading concentration. The data collected from this study can be useful to film manufacturers in fabricating nylon nanocomposite materials. Advisors/Committee Members: Pascall, Melvin.

▼ The ecology of the vegetable leaf surface is important to the survival and proliferation of enteric pathogens. Applying information about changes created by physical damage and phytopathogen infection on foodborne pathogens to the vegetable management practices can help minimize the hazard of contamination of fresh fruits and vegetables. Healthy plants were compared to physically damaged and bacterially infected lettuce plants for their ability to harbor Escherichia coli O157 over 10 days. Leaves from lettuce plants cracked along the central vein, plants infected with Xanthomonas campestris vitians, and healthy plants were inoculated with E. coli O157. Escherichia coli O157 were counted on these leaves and also on non-inoculated leaves for 10 days. While the density of E. coli O157 decreased on lettuce leaves for all three treatments, the decrease was greatest and most rapid on the healthy plants. There was limited dissemination of the enteric pathogen to non-inoculated leaves over the 10 day period. Counts of E. coli O157 on Xanthomonas-infected plants decreased significantly over 10 days while physically-damaged plants maintained stable counts. Contamination of vegetables with foodborne pathogens is a growing public health concern. Biotropic plant pathogens cause lesions and change the abundance and composition of exudates on leaf surfaces. Escherichia coli O157 proliferation was determined on tomato leaves infected with Pseudomonas syringae and Xanthomonas campestris. Gas chromatography was used to determine the sugars and sugar alcohols released by tomato leaves damaged by the same biotropic plant pathogens. The in vitro proliferation of E. coli O157, P. syringae, and X. campestris incubated in the presence of different combinations of exuded sugars was analyzed using a mixture model design. Escherichia coli O157 survived better on tomato plants damaged by Xanthomonas campestris than on healthy plants (P = 0.012). The most common sugars and sugar alcohols in the leaf exudate were glucose, fructose, inositol, and sucrose. The abundance of sucrose and inositol differed between the healthy and infected plants (P<0.05). Phytopathogen damaged increased nutrient availability and offered attachment sites for E. coli O157. Maintaining healthy plants might help limit the risks associated with foodborne pathogens on fresh vegetables. Advisors/Committee Members: Lee, Ken.

▼ Pressure-assisted thermal processing (PATP) is an alternative sterilization technique where elevated pressures (500-700 MPa) and temperatures (90-120 °C) are used for a short time to sterilize low-acid foods. In this research, the influence of barrier properties of packaging materials and storage conditions on selected quality attributes of PATP-treated baby carrots were evaluated. Carrots were vacuum packaged in three different pouches (Nylon/EVOH/EVA, Nylon/EVA and metallized polyester). Pouches were preheated and then immediately processed at 600 MPa and 110 °C for 10 minutes using a pilot scale high pressure food processor. Processed pouches were stored at 25 and 37 °C and withdrawn over 12 weeks of storage on a periodical basis and analyzed for color, β-carotene, and total mesophilic aerobic count. Oxygen transmission rates (OTR), water vapor transmission rates (WTR), melting point and enthalpy of fusion of the packages were evaluated. Dissecting and scanning electron microscope pictures were utilized to document the impact of processing on the packages. Results indicated that chosen processing parameters resulted in shelf stability of processed samples during 12 weeks storage at 25 and 37 °C. Packaging type, storage time and temperature significantly influenced (p < 0.05) product color and β-carotene content. Nylon/EVOH/EVA laminate pouch was the best pouch in terms of preserving color and β-carotene content of the carrot samples. The metallized polyester pouches were damaged by the PATP treatment. Following 12 weeks of storage increased the OTR of metallized polyester packages drastically (approximately 25 times at 25 °C and 45 times at 37 °C storage), which resulted in considerable changes (p < 0.05) in color and β-carotene content of the carrot samples. After 12 weeks of storage at 37 °C, Nylon/EVA, Nylon/EVOH/EVA and metallized polyester packages lost approximately 100, 36 and 100 % of β-carotene content, respectively. The red color of the carrot samples was reduced by 20, 87 and 72 % for Nylon/EVOH/EVA, Nylon/EVA and metallized polyester, respectively. There were slight changes in the melting points of the some polymers after PATP treatment. EVOH in Nylon/EVOH/EVA and polyethylene in metallized polyester pouch experienced significant decreases (p < 0.05) in the enthalpy of fusion values. Thermal analyses indicated a structural change in the polymers following PATP treatment. In summary, our study demonstrated the importance of utilizing high barrier packaging material for preserving quality attributes of PATP-treated carrots. Advisors/Committee Members: Balasubramaniam, Bala.

▼ Samples of unblanched (fresh), stannous chloride-treated or blanched jalapeño peppers were measured for real-time generation of lipoxygenase-derived volatiles during 10 min after tissue disruption. Volatiles were also measured before and after 1.5, 2.5, 3, 6 and 9 mo of frozen storage at -15°C. The concentration of all lipoxygenase-derived compounds was significantly higher in unblanched jalapeño peppers compared to enzyme inhibited peppers. The maximum concentration of (Z)-3-hexenal, (E)-2-hexenal, and hexanal was detected at about 1.2, 1.5, and 1.5 min after tissue disruption, respectively. A decrease in (Z)-3-hexenal and an increase in dimethyl sulfide and methylbutanal occurred in blanched peppers due to heat. Frozen storage resulted in no major changes in the LOX-derived volatiles of whole and pureed blanched peppers after 9 mo. However, in whole unblanched peppers a gradual decrease of (Z)-3-hexenal, (E)-2-hexenal, hexanal, hexenol and hexanol was observed over time; whereas in pureed unblanched peppers these compounds increased, reached maximum concentration and then decreased. Similarly, the minor LOX-volatiles 2-pentenal, 1-penten-3-one, (E)-2-heptenal, (E)-2-octenal, and (E)-2-nonenal showed an initial increase followed by a decline in both whole and pureed unblanched peppers. Tissue disruption increased generation and degradation rates during frozen storage. The compounds (E,Z)-2,6-nonadienal, n-propyl aldehyde, 2-isobutyl-3-methoxypyrazine, and a mixture of terpenes decreased in unblanched and blanched frozen samples; while nonanal and methylbutanal increased only in unblanched samples. Advisors/Committee Members: Barringer, Sheryl.

▼ In developed countries, a universal recommendation to improve overall nutritional status is greater consumption of vegetables. Bitterness of nutritionally beneficial cruciferous vegetables is a major reason for rejection. While sodium chloride can suppress bitterness, nutritional recommendations caution against over-consumption of salt. This study determined the minimum amount of salt required to increase palatability and suppress bitterness for three distinct age groups. College-aged panelists (Chapter 2) and Older panelists (Chapter 3) rated overall liking, saltiness, and bitterness of broccoli samples with varying levels of salt. They also indicated their perceptual ideals of saltiness and bitterness for broccoli. Younger panelists (Chapter 4) were asked to rank their preference for broccoli samples with varying levels of salt. The results of indicate that liking of cruciferous vegetables for all panels peaks somewhere between 150 and 450 mg of salt per serving. Highest overall liking, with adequate saltiness and suppressed bitterness, occurs around 350 mg. Advisors/Committee Members: Mangino, Mike.

▼ The production of volatile off-flavor compounds by lipid autoxidation is a major quality concern in foods. Photosensitizers such as chlorophyll can produce highly reactive singlet oxygen, thereby accelerating oxidation reactions. The objective of this research was to determine the effect of chlorophyll concentration on the production of volatile compounds in soybean oil, peanut oil and lard. Headspace volatile compounds were collected by solid phase microextraction and analyzed by gas chromatography and mass spectroscopy. The amounts of pentane, pentanal, 1-pentenol, 2-pentenal, hexane, 1-hexene, 2-hexanal, heptanal, 2-heptenal, 2-pentyl furan, 2,4,-heptadienal, 2,4-nonadienal, 1-octen-3-ol and 2-octenal were significantly affected by chlorophyll concentration with 1 to 2 days of light exposure. Relative to the triplet oxygen product hexanal, the singlet oxygen product 2-heptenal increased in quantity rapidly in soybean oil or peanut oil containing 5 ppm or 10 ppm chlorophyll when exposed to light even at 4 °C. The presence of chlorophyll was the most significant factor to the amount of volatile compounds during the first 2 days of light exposure; however, temperature was the most significant factor after 2 days of light exposure. Orange juice is the most predominant fruit juice in the U.S. market. Commercial orange juice is thermally processed to inactivate pectinmethylesterase (PME) and spoilage organisms. However, thermal processing can be detrimental to the flavor and nutritional qualities of the juice. High pressure processing (HPP) is a non-thermal processing method that can inactivate enzymes and undesirable microorganisms. The presence of CO2 in orange juice during HPP had been shown to enhance the inactivation of undesirable microorganisms. The effects of HPP, CO2-assisted HPP, and thermal processing on the inactivation of PME, volatile compound retention and ascorbic acid retention in Valencia orange juice was evaluated over 4 months of storage at 4 and 30 °C. Pressure magnitude, temperature, and dwell time were significant factors in the inactivation of PME. Pressure treatments resulted in insignificant volatile losses and <10% ascorbic acid reduction. The HPP+CO2 juice had the greatest cloud stability and highest ascorbic acid retention during storage. HPP+CO2 produced a cloud-stable orange juice with more ascorbic acid and flavor volatiles than the thermally processed juice. o The production of volatile off-flavor compounds by lipid autoxidation is a major quality concern in foods. Photosensitizers such as chlorophyll can produce highly reactive singlet oxygen, thereby accelerating oxidation reactions. The objective of this research was to determine the effect of chlorophyll concentration on the production of volatile compounds in soybean oil, peanut oil and lard. Headspace volatile compounds were collected by solid phase microextraction and analyzed by gas chromatography and mass spectroscopy. The amounts of pentane, pentanal, 1-pentenol, 2-pentenal, hexane, 1-hexene, 2-hexanal, heptanal, 2-heptenal, 2-pentyl furan, 2,4,-heptadienal, 2,4-nonadienal, 1-octen-3-ol and 2-octenal were significantly affected by chlorophyll concentration with 1 to 2 days of light exposure. Relative to the triplet oxygen product hexanal, the singlet oxygen product 2-heptenal increased in quantity rapidly in soybean oil or peanut oil containing 5 ppm or 10 ppm chlorophyll when exposed to light even at 4 °C. The presence of chlorophyll was the most significant factor to the amount of volatile compounds during the first 2 days of light exposure; however, temperature was the most significant factor after 2 days of light exposure. Orange juice is the most predominant fruit juice in the U.S. market. Commercial orange juice is thermally processed to inactivate pectinmethylesterase (PME) and spoilage organisms. However, thermal processing can be detrimental to the flavor and nutritional qualities of the juice. High pressure processing (HPP) is a non-thermal processing method that can inactivate enzymes and undesirable microorganisms. The presence of CO2 in orange juice during HPP had been shown to enhance the inactivation of undesirable microorganisms. The effects of HPP, CO2-assisted HPP, and thermal processing on the inactivation of PME, volatile compound retention and ascorbic acid retention in Valencia orange juice was evaluated over 4 months of storage at 4 and 30 °C. Pressure magnitude, temperature, and dwell time were significant factors in the inactivation of PME. Pressure treatments resulted in insignificant volatile losses and <10% ascorbic acid reduction. The HPP+CO2 juice had the greatest cloud stability and highest ascorbic acid retention during storage. HPP+CO2 produced a cloud-stable orange juice with more ascorbic acid and flavor volatiles than the thermally processed juice. Advisors/Committee Members: Min, David B.

▼ Lactic acid bacteria (LAB) and their bacteriocins have been used as natural food preservatives but only few reports are available concerning inactivation of gram negative bacteria by LAB bacteriocins. The objectives of this study were (1) to screen food for bacteria with activity against gram-negative pathogens, (2) to measure the sensitivity of selected foodborne pathogenic targets to the new antimicrobial agents, (3) to evaluate a synergy between the antimicrobial agent and high pressure processing (HPP) against the targeted pathogens, and (4) to study the combined effect of antimicrobial agent and HPP on components of bacterial cell . Lactobacillus curvatus OSY-HJC6 and L. casei OSY-LB6A were isolated from fermented foods and identified. The cell-free extracts (CFE) of these isolates showed inhibition against Escherichia coli p220, E. coli O157, Salmonella enerica serovar Enteritidis, Salmonella Typhimurium, and Listeria monocytogenes . The activity of the CFE from Lb. curvatus and Lb. casei was sensitive to pronase. The antimicrobial nature of CFE from both isolates was confirmed by eliminating the inhibitory effect of acid, hydrogen peroxide, and lytic bacteriophages . Lactobacillus curvatus showed antimicrobial activity extracellularly and intracellulary. Lactobacillus casei produces broad-spectrum complex bacteriocin-like substances. The combination treatment of CFE (32 CEAU/ml) and HPP (350 MPa for 1-20 min) synergistically inactivated E. coli O157 strains including O157:H7 and L. monocytogenes in cell suspension. The CFE (100 CEAU/g) and HPP (500 MPa and 400 MPa, 1 min) showed synergistic effect against E. coli O157 strains and L. monocytogenes in meat product. The effectiveness of CFE in combination with high pressure processing was more pronounced against L. monocytogenes . Differential scanning calorimetry thermogram suggested that ribosome and DNA in Listeria were damaged by the presence of CFE during HPP. The synergy between the CFE of Lb. casei and HPP suggests potential use of the combination treatment in food applications . Advisors/Committee Members: Yousef, Ahmed E.

▼ Antibiotic resistance (AR) in pathogens is a worldwide human health concern. The potential of food and enteric commensals as carriers of AR determinants to humans need to be clarified. Gastrointestinal microflora of 14 healthy individuals were examined for the presence of tetracycline-resistant bacteria and tetracycline-resistance genes. Results revealed a resistant count ranging from 106-109 CFU-mL-1, with non-resistant counts ranging from 106-1010 CFU-mL-1. The tetM gene pool determined by TaqMan real-time polymerase chain reaction ranged from 107-109 tetM gene copy number per gram. From the isolates examined, 8 distinct plasmid profiles were observed. DNA-DNA hybridization indicated the plasmid carriage of the tetM gene in some of the isolates. The regular inoculation of the colon with ART bacteria through the food chain is hypothesized as a significant contributor towards the enrichment of antibiotic resistant ART isolates and AR genes in the gut. Advisors/Committee Members: Wang, Hua.

▼ Gluten, the wheat protein that gives bread an open-cell crumb structure and flexibility, can not be tolerated by individuals afflicted with Celiac disease. The only treatment is life-long adherence to a gluten-free lifestyle. However, Celiac suffers crave many foods that contain gluten, such as bread, and therefore a need exists to provide high quality gluten-free baked goods. Hydrocolloids are commonly used to bind water and provide additional structure to gluten-free bread. However, published research has not studied the hydrocolloid alone, but in conjunction with alternative proteins contributing to the overall variability of the hydrocolloids behavior. To better understand the physicochemical changes imparted by hydrocolloids and protein on gluten-free bread, two hydroxypropyl methylcelluloses (HPMC) and xanthan gum were investigated at 2, 3, and 5% in rice cassava dough without the addition of alternative proteins. The formulated doughs were analyzed using thermoanalytic and rheological techniques to determine the role of water and subsequent flow behavior upon hydrocolloid addition. The baked loaves were then measured for specific loaf volume and tensile strength to determine loaf quality. The deconvoluted peaks of the derivatized thermogravimetric curves revealed that hydrocolloid-added dough held water tighter than the control with an additional water distribution at 85-88°C. While the increase of elastic moduli in the low methoxy HPMC and xanthan-added dough became more pronounced with addition, both HPMC formulations had increased viscous moduli allowing the gas cells to expand without collapsing. The final specific loaf volume increased with high methoxy HPMC loaves (2-5%) and low methoxy HPMC (2%) but was depressed with increased addition of low methoxy HPMC (5%) and xanthan (3 and 5%). Crumb firmness was decreased in high methoxy HPMC loaves but was increased significantly in low methoxy HPMC (5%) and xanthan (5%) formulations. From the formulations studied it was concluded that high methoxy HPMC was the optimum hydrocolloid in gluten-free dough.The rice cassava formulation with 5% high methoxy HPMC was further analyzed to determine hydrocolloid and alternative protein interactions with water in the gluten-free bread. Soy protein isolate was investigated at 1, 2, and 3% while egg white solids were investigated at 5, 10, and 15%. The formulated doughs were subjected to similar analysis as was performed for the hydrocolloid experiment. The addition of soy protein isolate and egg white solids reduced dough stability by suppressing HPMC functionality, reducing available water, weakening HPMC interactions with the starch matrix, and reducing foam stability. However, at 15%, egg white solids became the primary protein scaffolding in the dough and overcame negative interactions with HPMC, improving loaf volume and crumb regularity by forming an interconnected honeycomb matrix. Overall, while the addition of proteins and HPMC improved the rice cassava bread, there was an antagonistic interaction between the proteins and HPMC reducing the water binding ability and functionality of the HPMC. Advisors/Committee Members: Vodovotz, Yael.

▼ The cross-contamination of foods, especially raw fish and seafood products, is an important food safety problem. Seafood products can be cross-contaminated at the working environment, when food contact surfaces (e.g. processing equipment, utensils, knives, etc) bear a high number of microorganisms. In addition, raw seafood products can become contaminated when food handlers do not follow good manufacturing practices. Another important source of cross-contamination can be the ice in contact with raw seafood products and the water from this melted ice. Since ice is extensively used as a preservation method, ice prepared with safe sanitizers could be a promising alternative to reduce the potential for cross-contamination from raw fish and seafood products.The first part of this thesis (Chapter 2) reports an investigation on the stability (melting rate) of ice prepared with neutral electrolyzed water (NEW) and PRO-SAN® sanitizers and compared them with the stability of ice prepared with tap water. This first part also evaluated the efficacy of the sanitized ice in reducing the natural microbial burden on whole fish samples and in the ice used to store the fish. In addition, the efficacy of sanitized ice in reducing Escherichia coli K-12, Listeria innocua and Pseudomonas putida populations on Tilapia fish fillet samples and in storage ice was alsoevaluated. This was done by enumerating each bacterial species on the fish fillet and in the water from the melted ice at 12 and 24 hour intervals. This study found that sanitizing the ice did not affect its stability when compare with the control. Also, this study revealed that ice prepared with PRO-SAN® was effective in reducing the natural microflora washed off from the whole fish in both the water from the melted ice and in the ice that was in contact with the fish. In addition, this study found that ice prepared with PRO-SAN® and the NEW sanitizers had the ability to produce at least a 4 log reduction in E. coli, L. innocua and P. putida populations in the water collected when the ice melted. However, the overall reductions in the bacterial species on the fish fillet samples stored on sanitized ice were not different than the reductions obtained for the ice prepared with tap water. The second part of this thesis (Chapter 3) reports an investigation of the mechanisms used by PRO-SAN® and the NEW sanitizers to cause injury to the cells of E. coli K-12 and L. innocua. This was done by examining the bacterial cells using the transmission electron microscopic technique. The transmission electron microscope (TEM) images showed that the sanitizers altered the cell wall, internal membrane of E. coli and L. innocua. The results obtained for L. innocua revealed that this bacterium was more resistant to the bactericidal action of the NEW and PRO-SAN® sanitizers. This second part of this thesis confirmed that the mechanism used by various sanitizers against target microorganisms can be studied and understood using TEM. Advisors/Committee Members: Pascall, Melvin.

▼ The objectives of this study were to utilize enzymes, previously used in Cheddar cheese, to accelerate the ripening of Swiss cheese; to determine the chemical nature associated with the acceleration of ripening; to do descriptive sensory screening to identify the most promising enzyme; and to monitor the chemical changes associated with heat treatment to the samples. Initially, enzyme screening was done in cheeses of 150g and looking at a limited number of enzymes. Accelerzyme R CPG, peptidase enzymes, and Lipomod TM 621P – L621P, a mixed esterase, protease, and peptidase enzymes were used at different concentrations. Both enzymes increased bitterness and Lipomod produced a rancid flavor. Both bitterness and rancidity were reduced by heating the cheeses in a microwave. Since Lipomod gave the stronger flavors, further study was made with the enzyme at two concentrations in 5 pound cheeses. Gas Chromatography was used to measure the production of short chain free fatty acids. Acetic (C2:0) acid was produced in largest amount. Butyric (C4:0), and n-caproic (C6:0) acids were produced in significantly greater amounts in the high enzyme concentration treatment, which could be associated with the rancid flavor. Propionic (C3:0) and isovaleric (i-C5:0) acid concentrations were independent of the addition of enzyme. Swiss cheeses were analyzed by Fourier Transform Infrared (FTIR) spectroscopy to determine if they could be differentiated on the basis of enzyme addition. All samples were differentiated mainly based on short chain fatty acids, organic acids, and ester flavor compounds. Cheese made on different days gave different patterns, but still were differentiated on the basis of enzyme treatments. After 60 days of ripening, the overall flavor was intensified, and the rancid and bitter flavors were reduced by controlled heating the samples at 650C for 5 minutes without affecting the nutty and sweet flavors associated with Swiss cheese. The results of this study suggest that enzyme treatment may provide promise to meet the needs of the institutional markets desire for a Swiss cheese that provides better flavor after cooking. Further work is needed to develop a process for accelerating Swiss cheese flavor on a commercial basis. Advisors/Committee Members: Harper, W. James.

▼ Salmonella spp. is one of the leading microbial causes of foodborne illness in the United States with over 43,000 reported cases in 2007. This has shown an increase over the past several years, while many of the other pathogens most often linked to animal products have decreased. Production facilities with less than 500 employees face unique challenges, such as lack of technical support, financial and physical flexibility. These processors make a wide array of products. These unique challenges necessitate identifying processing conditions and sanitation protocols that correlate with reduced Salmonella contamination. Using the results from the FSIS 2005 Salmonella test sets, a case-control study was designed to address this need. The small and very small plants that failed test set A were selected as cases (n=32) and controls were matched to the case plants by inspection district and size, 4:1. Control plants had completed and passed the A set tests. The survey instrument was created in 3 parts: General HACCP, Slaughter, and Raw Product Processing. The slaughter survey contained additional questions regarding livestock species-specific practices. Surveys were completed by telephone with company representatives familiar with the establishments' HACCP plans and sanitation practices. The response rates were 40% and 38% for case and control plants, respectively. This study found few differences between the groups of processors; size and case/control status, but provides a valuable glimpse into the small and very small meat processors operations. Overall this survey exposed areas that these establishments are doing well, such as woven glove sanitation and maintenance tool sanitation. Area that need much improvement were also exposed; identification of Salmonella as a hazard likely to occur and the implementation of interventions into the processes. Additional details from these plants could provide more useful information for Salmonella control in smaller processing facilities. Results from this research will help focus and expand specific Extension programs for small and very small meat processors. Advisors/Committee Members: Knipe, C. Lynn.

▼ The effect of milk and milk components on the deodorization of diallyl disulfide, allyl methyl disulfide, allyl mercaptan, allyl methyl sulfide, and methyl mercaptan in the headspace of garlic as well as in the mouth- and nose-space after garlic ingestion was investigated using a selected ion flow tube-mass spectrometry (SIFT-MS). Fat-free and whole milk significantly reduced the head-, mouth-, and nose-space concentrations of all volatiles. Water was the major component in milk responsible for the deodorization of volatiles. Due to its higher fat content, whole milk was more effective than fat-free milk in the deodorization of the more hydrophobic volatiles diallyl disulfide and allyl methyl disulfide. Milk was more effective than water and 10% sodium caseinate in the deodorization of allyl methyl sulfide, a persistent garlic odor, in the mouth after garlic ingestion. Addition of milk to garlic before ingestion had a higher deodorizing effect on the volatiles in the mouth than drinking milk after consuming garlic. Advisors/Committee Members: Barringer, Professor Sheryl A.

▼ Fortification of snack foods is growing due to increasing consumer demand for healthier products. According to the Snack Food Association, total sales of snack foods in the U.S. grossed 26 billion dollars a year and corn based snacks accounted for 21.8% of total sales. Many snack foods produced in the U.S. are fortified with vitamins and minerals to improve their nutritional quality. The objective was to develop a real-time methodology for monitoring the uniformity of vitamins and minerals during fortification using a handheld infrared sensor. A fortification blend of zinc, iron, vitamin E, and calcium was added to whole grain corn meal at different levels (0.65% to 5.65%) and mixed for 30 minutes to obtain a homogeneous matrix. For real-time infrared analysis, aliquots (0.1g) were placed onto an ATR diamond crystal of a handheld spectrometer with pressure being applied to obtain good contact between the sample and the crystal. Spectra were collected in the 4000-700 cm-1 range. Distribution uniformity of the supplements was verified by high pressure liquid chromatography (HPLC). Partial least squares regression (PLSR) analysis was used to correlate the concentration of supplemented vitamins and minerals in the whole grain corn meal with the infrared spectra. The model predicted the level of fortification in corn meal using the infrared region between 885 to 1225 cm-1 (r=0.98, 5 factors). The standard error of cross-validation was <0.35% which gives potential to be used as a new tool in the industry. By using a simple, handheld FT-IR instrument, a methodology for real time monitoring of corn meal fortification was developed for the snack food industry to monitor corn-based extruded snack products. This could provide the snack food industry with a simple, real-time method to ensure the homogenous fortification of snack foods. Advisors/Committee Members: Rodriguez-Saona, Luis.

▼ Anthocyanins are among the most abundant polyphenols in fruits and vegetables and exhibit potent antioxidant activity. Our previous studies suggested that anthocyanins present in the gastrointestinal tract (GIT) of rats exert chemopreventive effect on colon cancer. Since such effect was dose dependent, it is important to examine the stability and transformation of anthocyanins in the GIT. Based on some in vitro studies and limited in vivo evidence, we hypothesized that anthocyanins were moderately stable under the influence of digestive enzymes and physiological conditions in the GIT, and their chemical structures determine the stability, accessibility, biotransformation, and health-promoting effects. To validate our hypothesis a series of studies were conducted. We first examined the transit, stability, transformation, and uptake of black raspberry anthocyanins in rat GIT. Our results suggest that ingested anthocyanin glycosides remained relatively stable in the GIT lumen and were efficiently taken up into the GIT tissues with limited transfer to the plasma compartment. We also observed selective degradation of cyanidin-3-glucoside in the small intestine lumen, which was tentatively attributed to β-glucosidase activity in the small intestine. In order to eliminate interferencing non-anthocyanin compounds in bioassays, a novel mixed mode cation-exchange/reversed-phase (MCX) solid-phase extraction (SPE) technique was developed for high purity isolation of anthocyanins. The new technique achieved above 99% anthocyanin purity while maintaining excellent yield (93.6 ± 0.55%) and low cost. To elucidate the effect of intestinal enzymes on anthocyanin digestion, an in vitro model was employed. Cell-free extract of pig small intestinal mucosa and crude extract of lactase containing foods/supplement were examined with respect to their β-glycosidase activities on highly purified anthocyanins. Selective degradation of anthocyanin glucosides and galactosides was observed in the presence of small intestinal mucosa cell-free extract and lactase supplement extract, respectively. The type of aglycone also substantially affected the resistance of anthocyanins to enzymatic degradation. The outcome of this dissertation demonstrates that chemical structure of anthocyanins greatly affects their stability in the GIT. Such information will contribute to the exploration of anthocyanin's health benefits in vivo, and may eventually facilitate the development of value added foods/nutraceuticals that promote the healthiness of people. Advisors/Committee Members: Giusti, Mónica.

▼ Fourier-Transform infrared (FT-IR) spectroscopy is a simple, fast and highly specific technology that can provide valuable insights into the complex chemical make-up of foods. Infrared provides tools, especially in the fingerprint region of the spectrum, to detect specific compounds in biological systems without the use of time-consuming methods or the use of hazardous organic solvents. Advances in FT-IR instrumentation and pattern recognition techniques have made it possible to extract information related to composition and conformation of food components from the spectra. We have evaluated the capability of infrared spectroscopy in classification and quantification of chemical compounds of interest for the dairy (butter) and tomato industries. Authentication is a critical quality issue for organic products since consumers are willing to pay 10-40% price premiums. There is a need for rapid and reliable analytical tools for determination of authenticity since traditional methods often involve time-consuming and laborious processes. Our objective was to evaluate the application of infrared spectroscopy combined with pattern recognition techniques to discriminate among organically and conventionally-produced butter in relation to quality and authenticity. Spectra from butter purchased from a local market (Columbus, OH) were collected by using Attenuated total reflectance (ATR) spectroscopy and analyzed using soft independent modeling of class analogy (SIMCA), a multivariate classification technique. This simple protocol generated unique mid-infrared signature profiles that permitted the chemically-based classification of butter samples based on manufacturer and production practice (organic vs. conventional). By using the spectral region from 1400-800 cm-1, multivariate (SIMCA) modeling showed well-separated clusters that discriminated among butter samples according to manufacturer, due to -HC=CH- trans bending out of plane vibration modes, (966 cm-1) presumably attributed to conjugated fatty acids. Infrared spectroscopy combined with multivariate analysis provides a simple and efficient tool for monitoring butter authenticity with minimal sample preparation. The objective of the second study was to develop a simple, accurate and cost effective protocol using ATR-IR spectroscopy and multivariate analysis to determine sugars in tomatoes. Tomatoes, the second most produced and consumed vegetable in the United States, are classified for use as fresh or processed tomato products based on their sugar and acid profile. Current methods to analyze sugar content of tomatoes are time and labor intensive making efficient assays for quantification desirable. Samples were obtained from genetically diverse tomato varieties that encompassed hybrids and elite parents used in the processing and fresh market industry. Samples were centrifuged, the supernatant vacuumed dried on a ZnSe crystal and infrared spectra collected. Enzymatic kits for glucose and fructose were used as reference methods. Multivariate models (PLSR) accurately predicted glucose and fructose using the supernatant with R-values > 0.98 and SECV <0.25g/100g, using the fingerprint infrared region of 1200-900cm-1 for sugars. Vacuum drying of the sample onto the ATR crystal caused spectral artifacts in some samples. ATR-IR combined with chemometrics could provide the tomato industry with a simple and high throughput method for determination of sugars in tomatoes that could lead to improved varieties with enhanced characteristics for industry and consumer demands. Advisors/Committee Members: Rodriguez-Saona, Luis.

▼ The kinetics of riboflavin photodegradation was studied. Lumichrome and lumiflavin were identified as the major photodegradation products. The effects of riboflavin, lumiflavin, and lumichrome on the flavor stability of soymilk were studied. The photodegradation of riboflavin after 24 h were 66% in D 2 O and 40% in H 2 O, respectively. The results indicate singlet oxygen was involved in riboflavin photodegradation. Ascorbic acid could protect riboflavin from photodegradation. When 0 mM or 160 mM ascorbic acid was included in riboflavin solution and stored under light for 96 h, the riboflavin degradation was 94.0% and 15.7%, respectively. Sodium azide reduced the degradation of riboflavin under light with a different mechanism. Ascorbic acid quenched both singlet oxygen and excited triplet riboflavin, sodium azide quenched only the singlet oxygen in riboflavin solution. The singlet oxygen quenching rate of sodium azide was 1.547 x 10 7 M -1 s -1 . Steady-state kinetic analysis indicated that the reaction rate between riboflavin and singlet oxygen was 1.01 x 10 10 M -1 s -1 . This diffusion-controlled reaction rate explained the rapid degradation of riboflavin in foods under light. Lumichrome and lumiflavin were identified as the major photodegradation products from riboflavin. In neutral or acidic conditions, lumichrome was the only major degradation product while in basic condition, lumiflavin were also present as a degradation product. Riboflavin had significant effects on the headspace oxygen depletion and volatile compounds formation in soymilk under light (P<0.05). The effects were not significant (P>0.05) in the dark. The volatile compounds increased under light, but not in dark as the added riboflavin increased. Hexanal was identified as the major volatile compound in the riboflavin photosensitized soymilk. Ascorbic acid significantly inhibited the formation of hexanal and total volatiles in soymilk under light. To determine if lumichrome or lumiflavin could also act as an effective photosensitizer, we analyzed the headspace oxygen and headspace volatiles in soymilk samples supplemented with riboflavin, lumichrome, or lumiflavin. Similar to riboflavin, lumichrome and lumiflavin caused significant headspace oxygen depletion and headspace volatile formation under light. The results indicated that lumichrome and lumiflavin were also effective photosensitizers. Ascorbic acid can be added to reduce the flavor changes in soymilk. Advisors/Committee Members: Min, David.

▼ The demand for foods that provide a health benefit beyond basic nutrition is on the rise. Prebiotics are non-viable food components that promote growth of a number of beneficial bacteria that naturally inhabit the human intestine. Some of these beneficial bacteria, such as Lactobacillus and Bifidobacterium species, are capable of eliciting health benefits such as reduced incidence of lactose intolerance and diarrhea, improved immune response and reduced cancer risk. The present studies address the effect of gluconate, a component of many foods and food supplements, on human intestinal microflora. Genes involved in gluconate metabolism in Lactobacillus reuteri were characterized. The effect of dietary gluconate supplementation on human intestinal populations of Lactobacillus, Bifidobacterium, Propionibacterium , and Escherchia coli was assessed over a 7-week period. Weekly stool samples were collected from 12 subjects and selected bacterial populations were enumerated. Colonies were subsequently grown on medium containing glucose or gluconate as the primary carbon source. At the level tested, dietary calcium gluconate did not significantly affect the overall quantity of Lactobacillus, Bifidobacterium, E. coli or Propionibacterium in most of the subjects tested. However, the proportion of gluconate-fermenting Lactobacillus and Propionibacterium strains increased upon gluconate consumption in some subjects, suggesting that a shift in species composition may occur. Speciation using the 16S-23S rRNA intergenic spacer region showed 2-6 different gluconate-fermenting Lactobacillus species in each subject and 11 different species overall. A 500 base pair (bp) putative gluconate kinase and a 750 bp putative gluconate permease fragments were found in the Lactobacillus reuteri 100-23 genome by amplifying DNA with degenerate primers. A gluconate-negative mutant of L. reuteri 100-23 was constructed via homologous recombination utilizing the putative gluconate permease fragment. The mutant (100-23D) and wild-type strains were characterized for gluconokinase, 6-phosphogluconate dehydrogenase and gluconate uptake activities. The mutant had significantly lower gluconokinase and gluconate uptake activities compared to wild-type. This suggests that gluconate genes in L. reuteri 100-23 are induced by gluconate and potentially arranged in an operon. Transcriptional analysis of wild-type and mutant strains showed a single transcript, indicating the gluconate permease gene is constitutively transcribed, and not inducible, in the presence of glucose or gluconate. Advisors/Committee Members: Yousef, Ahmed.

▼ Interest in purple corn (Zea mays L.) as a natural colorant has increased because of their potential health benefits. This study evaluated an anthocyanin-based purple corn extract as a natural colorant and chemoprotective source as compared to other anthocyanin sources. The structure/function relationship between anthocyanins and relative biological activity were investigated. Purple corncob contained high monomeric anthocyanins concentration (290 to 1323 mg/100g DW) and acylated anthocyanins (35 to 54%). Obtaining a colorant from purple corn produces large amounts of a highly colored purple corn waste (PCW) with limited solubility. The limited solubility was associated with the complexation of anthocyanins with macromolecules (tannins and proteins) abundant in PCW. The purple corn pigment extraction procedure was modified to minimize waste production. Deionized water at 50°C yielded high anthocyanin concentration with relatively low tannin and protein content. Application of a neutral protease during processing might decrease the level of the major protein (29KD) in purple corn and further reduce PCW. PCW was soluble in neutral environment and tested as a natural colorant for milk. PCW provided an attractive purple color (hue: 324-347°) to milk. This color was more stable in milk than in a pH6.8 buffer, suggesting that milk components protected anthocyanins and color in an accelerated model (70°C). Purple corn colorant showed higher inhibition of human colon carcinoma HT29 cell proliferation (GI50=~14µg/ml) than other six (chokeberry, bilberry, grape, purple carrot, radish, and elderberry) anthocyanin-rich extracts (ARE) (GI50 =31~130µg/ml). Anthocyanin-rich (2.29g/100g) PCW showed high antiproliferation (GI50 =21µg/ml), but lower than the purple corn colorant, suggesting that macromolecular complexes might trap monomeric anthocyanins reducing their bioavailability. An anthocyanin fraction separated from other phenolics in ARE played a major role on ARE chemoprotection. The interaction between anthocyanin and other ARE phenolics on chemoprotection was additive. Anthocyanin chemical structure affected chemoprotection: cyanidin 3-glucoside had higher inhibitory effect than pelargonidin 3-glucoside. Anthocyanin monoglucosylation showed a higher inhibitory activity than the corresponding 3,5-triglucoside. Effect of acylation on chemoprotection was dependant on the type of aglycone and acylating acid. More research is needed to better understand the impact of anthocyanin structure on chemoprotection. Advisors/Committee Members: Schwartz, Steven J.

▼ Diets rich in colorful fruits and vegetables have been found to correlate with lower incidence of certain cancers. In particular, black raspberries have been shown to inhibit multiple stages of oral, esophageal and colon cancer. At The Ohio State University, the mechanisms by which black raspberry compounds are chemoprotective are under exploration. The objective for this study was to evaluate how compositional variability impacts the antiproliferative activity of 75 black raspberry samples using an in vitro colon cancer cell model.Polyphenolics from black raspberries were extracted, semi-purified and lyophilized to obtain black raspberry extract powders. Human HT-29 colon cancer cells grown in 96-well plates were treated with freeze-dried black raspberry extracts at concentrations of 0.6 and 1.2 mg extract/mL media. Percent growth inhibition for each concentration of the extracts was determined using sulforhodamine B assay. Chemical composition of the extracts was also monitored by spectrophotometric and chromatographic techniques. All samples tested significantly inhibited the growth of HT-29 colon cancer cells in a dose-dependant manner. Inhibition of cancer cell proliferation obtained with different extracts ranged from 33-118%, with values higher than 100% inhibition indicating cytotoxic effects of the extracts. Cultivar, growing location and maturity all affected compositional characteristics of black raspberries, and these changes affected their ability to inhibit cancer cell proliferation. Data suggests that interaction of different berry components, rather than one class of compounds may be responsible for the inhibitory action of black raspberries on HT-29 colon cancer cells. These data may aid basic scientists, horticulturists, as well as the general population in the identification of fruits with the greatest potential to prevent and/or reduce the development of chronic disease. Advisors/Committee Members: Giusti, M. Monica.

▼ In-shell thermal pasteurization of eggs has adverse effects on the appearance and functionality of eggs. Ozone-based processing is an alternative technology with potentially fewer adverse effects as it is less thermally intrusive. There are no consumer acceptance studies published on either the appearance or the taste of ozone-treated eggs. This study examines whether consumers can detect differences when comparing ozone-treated eggs to commercially available pasteurized eggs and to fresh unpasteurized eggs. A visual difference test evaluating the appearance of freshly cracked uncooked eggs and a consumer affective test evaluating microwave scrambled eggs made from freshly cracked whole shell eggs was conducted. Visual panelists evaluated eggs on cloudiness of the albumen and yolk, spread of the albumen and yolk, height and color of yolk and overall visual appeal using 10-point linear scales. The yolks and albumens of the thermal treated and ozone-treated eggs were perceived as significantly cloudier than the unpasteurized control while the ozone-treated were perceived as more similar to the control (p < 0.05). The yolks of the ozone-treated eggs had a significantly lower heights and greater spreads than the other treatments (p < 0.05). Despite these differences, overall visual appeal of ozone-treated eggs was not significantly different from control. In the consumer affective test, panelists used 9-point hedonic scales to evaluate overall liking, appearance, aroma, flavor, and texture. Just-About-Right scales were used to rate the appeal of color, moistness and texture. There was no treatment effects on degree of liking on any of the attributes. The major difference in egg appeal was in moistness, where thermal treated and ozone-treated eggs were perceived as drier relative to the control but not compared to each other. This did not affect overall liking scores. This shows no adverse effects on consumer acceptance of eggs treated by the ozone process, with acceptance not different from unprocessed control on overall appearance or taste. These findings are useful when considering ozone-pasteurization to enhance the safety of fresh whole shell eggs to meet the goals of the U.S. Egg Safety Action Plan. Advisors/Committee Members: Lee, Dr. Ken.

▼ Prostate cancer is the second leading cause of cancer death in men, and diet is thought to play a role in the development of this disease. The “Westernized” diet, rich in red meat and dairy products, is associated with increased prostate cancer risk. Despite the negative perception of dairy products, milk contains several components, such as whey proteins and sphingomyelin (SM), which may play a role in prevention and/or treatment of prostate cancer. Whey proteins are a cysteine-rich protein source, and consumption of these proteins can elevate plasma concentrations of the antioxidant glutathione (GSH). Elevation of prostate GSH may reduce inflammation that is associated with cancer development. SM is a phospholipid that can induce apoptosis in cancer cells, and consumption of SM is associated with reduced incidence of colon cancer in mice. It is hypothesized that SM may also limit the proliferation of prostate cancer cells. The present studies were designed to examine the role of whey proteins and SM in prostate cells to determine if there is a potential role for these dairy components in prostate cancer prevention and treatment. First, the effects of oxidative stress in non-cancerous prostate cells was examined. Next, we examined the elevation of GSH in non-cancerous prostate cells by hydrolyzed whey proteins. Finally, the antiproliferative effects of SM in human prostate cancer cells were studied. The results of the present study revealed that bovine pituitary extract, a supplement used in the growth medium of the non-cancerous prostate cells, provides significant protection against oxidant-induced cell damage and may represent a confounding variable when studying oxidative stress in cell lines requiring this supplement. Hydrolyzed whey proteins elevated GSH concentrations in non-cancerous prostate cells by 64% and this GSH elevation protected the cells against oxidant-induced cell death. Exogenous SM significantly reduced prostate cancer cell proliferation by 17% after 24 h incubation, and this reduction was, in part, due to apoptosis. Taken together, results from these studies suggest a potential role for whey proteins and SM in reducing the risk for development of prostate cancer. Advisors/Committee Members: Harper, W. James.

▼ Riboflavin is a photosensitizer to produce singlet oxygen. The compound formed from riboflavin under light was positively identified as 2,3-butanedione by a combination of gas chromatographic retention time, mass spectrum and odor evaluation of authentic 2,3-butanedione. The addition of sodium azide, a singlet oxygen quencher, minimized the formation of 2,3-butanedione from riboflavin. The 2,3-butanedione was formed from the reaction between riboflavin and singlet oxygen. The effects of 0, 100, 200, 300, 500, and 1000 ppm of alpha-, beta-, gamma-, and delta-tocotrienol on the oxidation of lard in the dark at 55°C for 7 days were determined by measuring headspace oxygen and peroxide value. The 100 ppm alpha- or beta-tocotrienol was the most effective antioxidant. Gamma- or delta-tocotrienol at all concentrations significantly lowered the oxidation of lard. The antioxidative activities were in delta- > gamma- > beta- > alpha-tocotrienol. The selection of type and optimum concentration of tocotrienol can minimize the oxidation of lipids and be economically important. Samples of 0.1, 0.25, or 0.4 M lard in methylene chloride containing 4.4 × 10 -6M chlorophyll b and 0, 0.3, 0.6, or 0.9 mM alpha-, beta-, gamma-, or delta-tocotrienol were prepared and stored at 3,000 lux for 4 hours to study the quenching mechanisms of tocotrienols on the chlorophyll photosensitized oxidation of lard. The steady state kinetic study showed that tocotrienols acted as singlet oxygen quenchers. The reaction rate of singlet oxygen with lard was 6.5 × 10 4M -1sec -1. The singlet oxygen quenching rates of alpha-, beta-, gamma-, and delta-tocotrienol were 2.16 × 10 7, 1.99 × 10 7, 2.05 × 10 7, and 0.80 × 10 7M -1sec -1, respectively. Alpha-tocopherol in foods is oxidized during the processing and storage. The effects of 0, 250, 500, 1000 and 1500 ppm of oxidized alpha-tocopherol on the oxidation of purified soybean oil in the dark at 55°C for 6 days were studied. The oxidized alpha-tocopherol acted as prooxidant. The prooxidant mechanism may be due to intermediate compounds such as hydroxyl, peroxy or oxy radical and singlet oxygen formed during the oxidation of alpha-tocopherol. The prevention of tocopherol oxidation and removal of oxidized tocopherol could improve the oxidation of foods. Advisors/Committee Members: Min, David B.

▼ In recent years, consumption of fresh vegetables has greatly increased and consumer's demand for fresh or minimally-processed fresh food (MPF) is on the rise. The risk of contamination by spoilage and pathogenic microorganisms, and growth of these contaminants are of concern because most of these products are consumed without thermal processing. In addition, the recent outbreaks of foodborne diseases caused by Escherichia coli O157:H7, Hepatitis A, and Camphylobacter jejuni raised serious questions about the safety of minimally processed food. Chlorine has been used to decrease the microbial load during vegetable processing; however, it can react with organic compounds, resulting in the formation of carcinogenic trihalomethane compounds. Therefore, many studies were done to find suitable alternatives to chlorine. For decades, researchers recognized the germicidal action and oxidizing potential of ozone. Ozone applications in the food industry are mostly related to decontamination of product surfaces and water treatment. Ozone has been used with mixed success to inactivate contaminant microflora on meat, poultry, eggs, fish, fruits, vegetables and dry foods. Additional research is needed to elucidate the kinetics and mechanisms of microbial inactivation by ozone and to optimize its use in food applications. The objectives of this research were: 1) to study the patterns of inactivation of selected spoilage ( Pseudomonas fluorescens , Leuconostoc mesenteroides ) and pathogenic ( Listeria monocytogenes , Escherichia coli O157:H7) bacteria by ozone; 2) to explore mechanisms of microbial inactivation by ozone; and 3) to optimize the efficiency of ozonation procedures in lettuce processing. To study microbial inactivation patterns, a batch and three continuous reaction systems were tested. In the batch reactor, all tested microorganisms showed a similar pattern of inactivation. Microbial inactivation occurred immediately after addition of ozone with little change in counts thereafter. The population decreased 2.7 to 7.5 log cfu/mL in 30 seconds, when 1 mg/L ozone was used for the treatment. E. coli O157:H7 was the most resistant and L. monocytogenes was the least resistant to ozone inactivation. A dose-response model having two segments appeared adequate in describing inactivation of tested microorganisms. A continuous reaction system, using a membrane filter, was found suitable to study patterns of microbial inactivation as it minimizes the auto-decomposition of ozone during the reaction and thus a uniform concentration of ozone can be applied throughout the treatment. Inactivation kinetics for all the tested microorganisms revealed concave downward curves. E. coli O157:H7 was the most resistant and L. monocytogenes was the least resistant to ozone inactivation when tested in this continuous reactor. Application of 2.5 mg/L ozone decreased the count by 5 to 6 log 10 cfu/mL in 40 seconds. A log-log dose-response model described inactivation data appropriately. Interaction of ozone with microorganisms was elucidated by detecting cell injury and examining treated cells with a scanning electron microscope. When ozone was used at 0.55 to 1.85 mg/L, 51 to 78% of survivors were injured. The injured population was greater at intermediate rather than high C*t (mg/L x sec) values. Among the tested microorganisms, P. fluorescens was the most while L. monocytogenes was the least injured by ozone treatments. Electron microscopic analysis showed that ozone caused damage to the cellular structure; this damage was more pronounced in gram-negative than gram-positive bacteria. When treated with ozone, gram-positive bacteria seemed to lose some mucoid material outside the cell wall, whereas gram-negative cells tended to collapse and lose cellular components. Therefore, apparent structural integrity of the cell can not be correlated with degree of inactivation of microorganisms by ozone. The feasibility of using ozone to decontaminate a minimally processed product (i.e., shredded lettuce) was explored. Different ozonation media and delivery methods were tested. Ozonation media include ozonated water, bubbled ozone gas into water, and gaseous ozone. Delivery methods were tested to ensure intimate contact between ozone and the treated product. Delivery of ozone was facilitated by stirring, sonication and stomaching. Average decontamination by water washing, ozonated water, bubbling ozone was 0.9, 1.1, and 1.4 log 10 cfu/g, respectively. Bubbling ozone was significantly better than water treatment and also more efficient way of lettuce disinfection than ozonated water treatment. Among the delivery methods, high-speed stir was better for the decontamination of lettuce than other methods. Maximum inactivation of natural microflora (1.9 log cfu/g) was achieved by bubbling ozone with high-speed stir. Therefore, it was concluded that bubbling ozone treatment with high-speed stir will be the most efficient and applicable way for lettuce disinfection. In conclusion, inactivation studies on bacterial cell suspensions clearly indicate that ozone is a potent antimicrobial agent. Bactericidal action of ozone varies with the microorganism. Ozone at low concentrations damages the outer membrane of gram-negative bacteria and thus cause dramatic changes in the cell structure. Similar concentrations of ozone cause less damage to the cell wall of gram-positive bacteria, but the agent causes intercellular damage and effectively inactivates the cell. Ozone is a less potent antimicrobial agent against microorganisms in food than in pure cell suspensions. Successful application of ozone in food processing depends on developing methods to ensure good contact between this agent and target microorganisms on the treated food. Advisors/Committee Members: Yousef, Ahmed E.

▼ Lipid oxidation is a serious concern for the food industry, due to the production of off-flavors and odors, discoloration, and toxic compounds. Oxidation can also decrease the nutritional content in food products. There are two forms of oxygen which participant in lipid oxidation; singlet and triplet. Singlet oxygen (1O2) is a nonradical, high energy molecule that can react directly with fatty acids. Singlet oxygen can be formed during photosensitized oxidation, a process in which a photosensitizer, such as chlorophyll, absorbs light energy and becomes excited. Triplet oxygen (3O2)is the most stable and common form of oxygen. Autooxidation is triplet oxygen mediated lipid oxidation, and requires both the oxygen and the fatty acids to be in radical form. The lipid oxidation process can be slowed or prevented by compounds known as antioxidants. Tocopherols (α, β, γ, and δ), which are commonly known as vitamin E, have been showed to have antioxidant activity. The present study examines the effect of tocopherol isomers on chlorophyll photosensitized oxidation and heat induced autooxidation of lard. The effects of tocopherol isomers on lard oxidation were measured by headspace oxygen and peroxide value analyses. α-, β-, γ-, and δ-Tocopherol were all found to prevent photosensitized oxidation of lard by quenching singlet oxygen. α-Tocopherol had the highest singlet oxygen quenching rate at 1.42 x 107M-1s-1 followed by β-tocopherol (1.11 x 107M-1s-1), γ-tocopherol (9.70 x 106M-1s-1), and δ-tocopherol (4.23 x 106M-1s-1). Lard thermal stability was increased, via autooxidation inhibition, by γ- and δ-tocopherol. The optimum concentrations were determined to be 250-1000ppm and 500ppm for the γ- and δ-isomer, respectively. α-Tocopherol did significantly increase lard stability, but it was found to have significant prooxidant activity (p<0.05) at concentrations greater than 250ppm. Tocopherol isomers are able to inhibit both photooxidation and autooxidation in lard, however there is not one isomer that is superior than the others at preventing both types of oxidation. Advisors/Committee Members: Min, David B.

▼ The rapid emergence of antibiotic resistant (ART) pathogens poses a serious threat to public health. A large antibiotic resistance (AR) gene pool has recently been found in commensal bacteria associated with many retail foods. Subsequently, the question is whether these foodborne ART bacteria through daily food consumption are responsible for the prevalence of ART bacteria in human digestive ecosystems. To address this issue, the ART bacteria profiles in fecal samples of infant subjects before solid food consumption were analyzed by total plate counting of ART bacteria and real-time PCR assessment of the tetM gene pool. Tetracycline-resistant (Tetr) bacteria were found in fecal samples from both breast and formula-fed babies shortly after birth without being exposed to the corresponding antibiotic. The numbers of ART bacteria within these subjects increased rapidly within four weeks before reaching a relatively stable level. The numbers of ART bacteria ranged from 5.5x105 to 1.9x108 CFU/g of sample and was maintained throughout the 12 month examination period. Similar shift of the tetM gene pool in the infant fecal samples was observed by real-time PCR. The tetM gene pool in all infant fecal samples, with the exception of the meconium samples, ranged at least from 9.0x105 to 9.0x108 copies per gram of sample. The data suggest that routes other than conventional food intake may have played a role in the initial colonization of ART bacteria in infants. The impact of the ART bacteria from conventional food intake on the dynamic shift of the ART bacteria in human digestive tract at later stages through occasional colonization and maybe horizontal gene transmission is yet to be revealed. Advisors/Committee Members: Wang, Hua.

▼ Attention has been given to expand our knowledge in respect to the role of sulfur compounds in the flavor of aged Cheddar cheese. A new method, based on the concentration of reduced thiol compounds and their analysis by a sulfur-specific GC detector shows the presence of 39 thiol compounds in the aged Cheddar cheeses. Of these 14 were tentatively identified by Kovat’s indices and the presence of 4-mercapto-4-methyl pentan-2-one confirmed with a pure standard. These 14 thiol compounds possess an additional alcohol, aldehyde, or ketone functional group. The results of this method were substantiated by other analyses (descriptive sensory analysis and electronic nose). Sensory analysis showed that there were four different sulfur descriptors (total sulfur, egg-like, match-like and catty) that differenced the eleven cheeses. Total sulfur and catty were correlated to age of the cheese and catty and match-like were also correlated. The electronic nose, using a mass spectrometer in NCI mode, gave similar differentiation patterns to the sensory and also suggest that 4-mercapto-4-methyl pentan-2-one was associated with the differentiation of the aroma. The three analytical approaches all confirm the importance of sulfur compounds to the flavor of aged Cheddar cheese and all help support the significance of the poly functional thiols in Cheddar cheese flavor, especially the 4-mercapto-4methyl pentan-2-one (catty) compound. An additional 15 medium and higher molecular weight thiols were partially characterized by Kovat’s Retention Indexes, and their molecular weights were estimated within a range of a few grams. Attention has been given to expand our knowledge in respect to the role of sulfur compounds in the flavor of aged Cheddar cheese. A new method, based on the concentration of reduced thiol compounds and their analysis by a sulfur-specific GC detector shows the presence of 39 thiol compounds in the aged Cheddar cheeses. Of these 14 were tentatively identified by Kovat’s indices and the presence of 4-mercapto-4-methyl pentan-2-one confirmed with a pure standard. These 14 thiol compounds possess an additional alcohol, aldehyde, or ketone functional group. The results of this method were substantiated by other analyses (descriptive sensory analysis and electronic nose). Sensory analysis showed that there were four different sulfur descriptors (total sulfur, egg-like, match-like and catty) that differenced the eleven cheeses. Total sulfur and catty were correlated to age of the cheese and catty and match-like were also correlated. The electronic nose, using a mass spectrometer in NCI mode, gave similar differentiation patterns to the sensory and also suggest that 4-mercapto-4-methyl pentan-2-one was associated with the differentiation of the aroma. The three analytical approaches all confirm the importance of sulfur compounds to the flavor of aged Cheddar cheese and all help support the significance of the poly functional thiols in Cheddar cheese flavor, especially the 4-mercapto-4methyl pentan-2-one (catty) compound. An additional 15 medium and higher molecular weight thiols were partially characterized by Kovat’s Retention Indexes, and their molecular weights were estimated within a range of a few grams. Advisors/Committee Members: Harper, W. James.

Advisors/Committee Members: Morr, Charles V.

▼ Nonstarter Lactobacillus strains affect the quality of many cheese varieties. Though the use of Lactobacillus casei as an adjunct culture is common for Swiss-type cheese manufactured in Switzerland, few published reports exist on adjunct use and none exist for adjunct use in U.S.-manufactured Swiss cheese. The objectives of this study were to isolate and identify nonstarter Lactobacillus strains in high quality commercial Swiss cheeses and to investigate citrate metabolism among nonstarter lactobacilli, to study the effect of nonstarter Lactobacillus strains as adjunct cultures on Swiss cheese characteristics, and to determine chemical, microbiological, and physical characteristics of commercial Swiss-type cheeses. Lactobacilli were selected from domestic and European Swiss cheeses and the strains were genetically typed and speciated. Qualitative and quantitative citrate utilization assays were performed on each strain. The total lactobacilli counts ranged from 4.7 to 7.9 log CFU/g cheese. Strains belonging to L. casei , L. rhamnosus , and L. fermentum species were most frequently encountered. Lactobacillus casei strains predominated in the cheeses originating in Switzerland; whereas, the domestic cheeses contained a wider variety including different strains of L. casei , L. rhamnosus , L. gasseri , L. delbrüeckii , and L. fermentum . Among the strains tested, L. casei strains were strong citrate utilizers followed by L. rhamnosus , L. fermentum , and L. gasseri strains. A putative citP gene fragment from one citrate-utilizing L. casei strain was amplified, cloned, and sequenced. Distribution of the putative citP gene in Swiss cheese nonstarter lactobacilli was determined. Selected nonstarter Lactobacillus strains isolated from commercial cheeses were utilized as adjunct cultures for cheese manufacture. Lactobacillus casei strains utilized all citrate present in cheese before the end of the warm room ripening phase. There were no significant differences among cheeses in regards to protein, fat, moisture, and salt contents. However, sensory properties were affected. Fifteen commercial cheeses were analyzed for microbiological, physical, and compositional characteristics. These results will complement descriptive sensory and consumer preference studies. Understanding the occurrence, types, and metabolic capabilities of nonstarter Lactobacillus spp. in Swiss cheese will allow further studies of their role in cheese ripening and their effect on Propionibacterium fermentation. Advisors/Committee Members: Harper, James W.