Doctor of Philosophy / Department of Grain Science and Industry / Yong Cheng Shi / To realize the full potential of waxy wheat flours in food applications, six advanced hard waxy wheat lines were studied. Pasting properties of waxy wheat flours as well as factors governing the pasting properties were investigated. Waxy wheat starch granules swelled more extensively and were more prone to α-amylase degradation than normal wheat starch. A combination of endogenous α-amylase activity and protein matrix contributed to a large variation of pasting properties of waxy wheat flours. Bi-axial extension properties classified dough from waxy wheat as in-elastic. Waxy wheat flour had higher water absorption and lower mixing time than normal wheat flour. Waxy wheat starch affected protein hydration but not protein extractability after optimum dough mixing. Presence of some non-protein free thiol contents and some gliadins acting as chain terminators could be the underlying reasons for waxy wheat flours producing slack dough. In an effort to improve functionality of waxy wheat flours, hydro-thermal processing was used. Two temperatures (140 and 160°C), three moisture contents (0, 12.4 and 20%), and four exposure times (0, 5, 15, 30 and 60 min) were employed. Hydrothermal processing resulted in non-cohesive waxy wheat flours with high viscosity and greater acid stability than native waxy wheat flour. A closer investigation revealed the possible role of endosperm proteins in improving pasting properties of waxy wheat flours. Upon thermal processing, waxy wheat flours demonstrated a long hydration time before forming dough. Heating decreased protein solubility while no changes in starch molecular weight distribution were observed. Our results indicate that hydro-thermal processing results in increased starch protein interaction. As part of application of waxy wheat, bread was baked by replacing normal wheat flour with two hard waxy wheat flours at 15, 30, and 45% levels. Substitution with waxy wheat flour resulted in higher loaf volume and softer loaves. However, substitution at > 30% resulted in excessive post-bake shrinkage and a ‘key-hole’ shape with an open crumb structure. Bread crumb microstructure indicated a loss of starch granule rigidity and fusing of starch granules. Soluble starch content was significantly higher in bread 1-day old crumb containing waxy wheat flour than in control bread.

Doctor of Philosophy / Food Science Institute -- Animal Science & Industry / J. Scott Smith / Heterocyclic amines (HCAs) are produced in meats cooked at high temperature, which are potent mutagens and a risk factor for human cancers. Occurrence of HCAs in ready-to-eat (RTE) meat products and cooked meat products based on prevalence of various cooking methods that are preferred among U.S. meat consumers were investigated. The primary HCAs detected in samples were PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine), MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline), and DiMeIQx (2-amino-3,4,8-trimethyl-imidazo [4,5-f]quinoxaline). RTE meat products were ranked in the following order of increasing total HCA content: pepperoni (0.05 ng/g) < hot dogs and deli meat products (0.5 ng/g) < fully cooked bacon (1.1 ng/) < rotisserie chicken meat (1.9 ng/g) < rotisserie chicken skin (16.3 ng/g). In cooked meat products, high levels of total HCAs were found in fried pork (13.91 ng/g), fried fish (14.91 ng/g), and fried bacon (17.91 ng/g). Inhibition of HCAs by rosemary extracts, which were extracted with different solvents, were evaluated in cooked beef patties. Five rosemary extracts were 100W (100% water), 10E (10% ethanol), 20E (20% ethanol), 30E (30% ethanol), and 40E (40% ethanol). Rosemary extract 20E containing a mixture of rosmarinic acid (27.3 mg/g), carnosol (72.9 mg/g), and carnosic acid (4.2 mg/g) showed the greatest inhibition of MeIQx (up to 91.7%) and PhIP (up to 85.3%). The effect of enhancement and marination on HCA formation in meat products was investigated. The addition of salt and phosphate greatly improved the water-holding capacity and decreased HCA formation (up to 58%) in enhanced fresh meat products. An greater reduction of HCAs (up to 79%) was found in marinated fresh meat; the enhancement solution for this meat contained ingredients that exhibited good antioxidant properties.

Doctor of Philosophy / Food Science Institute -- Diagnostic Medicine/Pathobiology / David G. Renter / Salmonella and Escherichia coli O157 are important causes of foodborne illness in humans and have been associated with the consumption of undercooked, contaminated beef. Individual feedlot cattle may shed these organisms in their feces and subsequently contaminate cattle hides and carcasses at harvest. Preharvest and harvest interventions may significantly decrease the risk of beef contamination and subsequent risk of human illness. Previous research suggests that preharvest interventions for Salmonella or E. coli O157 may compliment harvest interventions and reduce the risk of carcass contamination. In my research, I used diverse study designs to develop a better understanding of the epidemiology of Salmonella and E. coli O157 and evaluate the impact of specific preharvest interventions in commercial feedlot cattle. A randomized controlled trial indicated that a commercially available vaccine did not affect the fecal prevalence of Salmonella, or health and performance of cohorts of feedlot cattle. However, the fecal prevalence of Salmonella varied by cohort, suggesting cattle source as a risk factor. In a repeated cross-sectional study, the fecal prevalence of Salmonella in cattle at feedlot arrival was not associated with the prevalence immediately prior to harvest, yet specific Salmonella subtypes, as defined by pulsed-field gel electrophoresis (PFGE), persisted throughout the feeding period. Another of my studies defined and compared PFGE subtypes of E. coli O157 isolated from cattle feces and carcass samples at harvest to determine relationships between fecal shedding and carcass contamination. Truckload appeared to be an important factor, and feces from cattle shedding both high- and low-concentrations of E. coli O157 posed a risk for carcass contamination. A stochastic Monte-Carlo modeling framework was later used to assess the impact of seasonal fecal prevalence and combinations of preharvest interventions on the risk of carcass contamination with E. coli O157. Results indicated that it may be important to incorporate multiple preharvest interventions, especially during periods of high fecal prevalence of E. coli O157. Overall, the research described in this dissertation demonstrates that multiple risk factors and interventions at the cohort level must be considered in order to mitigate the risks associated with Salmonella and E. coli O157 in beef production systems.

Master of Science / Department of Diagnostic Medicine/Pathobiology / Douglas A. Powell / The World Health Organization estimates that up to 30% of individuals in developed countries become ill from food or water each year, with up to 70% of these illnesses estimated to be linked to food service. Restaurant inspections aim to prevent restaurant-associated foodborne outbreaks while enhancing consumer confidence in the safety of food prepared in these establishments. Inspection disclosure systems have been developed as a tool for consumers and incentive for foodservice operators. Disclsosure systems are common in developed countries; however, they are inconsistent. Previous research has not determined the best format to disclose inspection results to the public while providing incentives for operators. This research aimed to develop a consistent, compelling and trusted disclosure system for New Zealand. The research evaluated existing disclosure systems operating internationally and nationally. The national review interviewed with Environmental Health Officers (EHOs)(n=8), operators (n=109) and consumers (n=244), and findings were used for card designs. Cards were evaluated internally (n=43), then by 11 focus groups (n=68). Two cards, letter and gauge, were introduced to food premises (n=371) in six districts for three months for evaluation. Operators (n=269) and consumers (n=991) were interviewed to determine which design best communicated inspection results. The majority of operators indicated they had not received consumer feedback about the card, and half felt the card was something consumers would use. Less than half of consumers indicated they noticed cards prior to entering a premises; from these data it appeared the letter attracted more initial attention (78% of respondents) than the gauge (45%). Consumers indicated card placement was an important factor in noticing cards. Nearly all interviewed consumers indicated they expected cards at restaurants, take-aways and fish n’ chips shops. When asked which card they preferred, 58% (n=38) of operators with the gauge preferred the letter; and 79% (n=47) of operators with the letter preferred the letter. Consumer preference was for the letter, with 88% (n=133) of those in gauge districts preferring the letter, and 72% (n=161) of those in letter districts preferring the letter. Based on these data the letter card was recommended for a national inspection disclosure system for New Zealand.

Master of Science / Department of Grain Science and Industry / Sajid Alavi / Plastics from petroleum sources are the main raw materials used for producing food packaging films. But these plastic films cause a great environmental concern due to their non-degradable nature and non-renewable source. Biodegradable polymers like starch can be used as a base material which can replace petroleum based plastics packaging. In this study, starch (0-80%) and polyvinyl alcohol (PVOH) (20-100%) were used as base polymers to produce nanocomposites. Glycerol (30%) and sodium montmorillonite (0-20%) were used as a plasticizer and nano-filler, respectively. Nanocomposites were produced through two methods: solution and melt extrusion method. Extrusion method resulted in greater exfoliation of nanocomposites than solution method because it provided more shear stress to disrupt the layered silicate structure. In extrusion method, a lab scale extruder was used to produce these nanocomposites and films were made by casting. Process parameters, including screw speed (200-400 RPM) and barrel temperature (145-165[superscript]oC), were varied systematically. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were conducted to characterize the nanostructure of these nanocomposites. Thermal characterization of these films was carried out through differential scanning calorimetric (DSC) studies. Results from XRD and TEM explained the phenomenon of intercalation and exfoliation in these nanocomposites. Structural and thermal data indicated important role for Na[superscript]+MMT along with process parameters in controlling exfoliation and glass transition temperature of the nanocomposites. These results also helped in understanding the fundamental interactions among all the components. The tensile strength and elongation at break of films ranged from 4.72 to 23.01MPa and 63.40 to 330.15% respectively, while water vapor permeability ranged from 1.68 to 0.79g.mm/kPa.h.m[superscript]2. These results provide a great understanding for further improvements in order to bring these films close to commercial plastic films which have superior tensile strength (10-80MPa), elongation at break (200-800%) and water vapor permeability (0.002- 0.05g.mm/kPa.h.m[superscript]2). The cost for polyethylene is approximately $0.70/lb while the raw material cost for this starch based films is approximately $0.85/lb.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Donghai Wang / Scott R. Bean / Sorghum has been considered one of the best species dedicated to biofuel production because of its drought tolerance, low fertilizer or pesticide input, established production systems, and genetic diversity. The mission of this research was to better understand the relationship among "genetic-structure-function-conversion." The main focus of this research was to study the impact of sorghum proteins on ethanol fermentation and to investigate novel methods for evaluation of sorghum fermentation quality. Changes of sorghum protein in digestibility, solubility, and microstructure during mashing were characterized. Sorghum proteins tended to form highly extended, strong web-like microstructures during mashing. The degree of protein cross-linking differed among samples. Formation of web-like microstructures due to cross-linking reduced conversion efficiency. A rapid method for extracting proteins from mashed and nonmashed sorghum meal using sonication (ultrasound) was developed, with which the relationships between the levels of extractable proteins and ethanol fermentation properties were determined. There was a strong relationship between extractable proteins and fermentation parameters. Ethanol yield increased and conversion efficiency improved significantly as the amount of extractable proteins increased. The Rapid-Visco Analyzer (RVA) was used to characterize pasting properties of sorghum grains. Results showed a strong linear relationship between ethanol yield and final viscosity, as well as setback. A modified RVA procedure (10 min) with an application of α-amylase was developed to simulate the liquefaction step in dry-grind ethanol production. There was a remarkable difference in mashing properties among the sorghum samples with the normal dosage of α-amylase. The modified RVA procedure is applicable not only for characterization of mashing properties but also for prediction of tannin content and for optimization of [alpha]-amylase doses for starch liquefaction. A small-scale mashing (SSM) procedure requiring only 300 mg of samples was investigated as a possible method of predicting ethanol yield of sorghum grain. There was a strong linear correlation between completely hydrolyzed starch (CHS) from SSM and ethanol yields from both traditional and simultaneous saccharification and fermentation procedures. CHS was a better indicator for predicting ethanol yield in fermentation than total starch.

Master of Science / Food Science Institute / Daniel Y.C. Fung / James L. Marsden / Listeria monocytogenes is known to be an environmental contaminant in food processing facilities. Floor drains in processing environments harbor Listeria spp. due to continuous presence of humidity and organic substrates. The cleaning and washing activities undertaken may translocate the bacterial cells from the drain to the surrounding environment, thus contaminating food products being produced. This study validates the effectiveness of Johnson Diversey ‘Eliminex’ Foaming Drain Cleaner and Johnson Diversey ‘Final Step’ 512 sanitizer for inhibition of Listeria monocytogenes in drain surfaces and evaluates the potential for translocation of L. monocytogenes from drains to food contact surfaces in the surrounding environment using Listeria innocua as a surrogate. A 7x 7 x 8 feet flexi glass chamber was built in which a 10 inch diameter drain mounted on an aluminum cabinet was placed. The drain was inoculated with the surrogate organism, L. innocua, at specific time intervals and then treated with the given chemicals. Sponge samples were taken and bacterial populations were recovered on Tryptic Soy Agar (TSA), Modified Oxford Medium (MOX) and Thin Agar Layer MOX (TALMOX). Stainless steel coupons (6.4 x 1.9 x 0.1 cm) were hung at 3 different heights 1, 3 and 5 feet inside the chamber and cell translocation from the drain on to the stainless steel coupons was studied. Reductions up to 4 Log CFU/area or ml were seen at the drain surface, drain crate, drain pipe and wash water for both free cells and cells entrapped in biofilms Treatment had a significant effect (p<0.05) on the reduction of bacterial cells. The wash water showed the greatest reduction from 8 Log CFU/ml to est. 0.23 Log CFU/ml. The given cleaner and sanitizer were found to be effective for reducing Listeria spp. on drain surfaces. Results for the second part indicated translocation at all three heights with percentage translocation ranging between 2-17%. Significantly higher translocation (p<0.05) was seen at 1 foot, followed by 3 feet and 5 feet indicating the closer the height to the drain, the greater the number of bacterial cells that are able to transfer from the drain to the surrounding environment.

Master of Science / Food Science Institute / J. Scott Smith / The tortilla segment of the Mexican food market in the United States is rapidly growing. Tortillas are being used in many different mainstream applications, including wraps, lasagna, pizza, and appetizers. In 2000, the tortilla market was a $4 billion industry and with more than 85 billion tortillas consumed in the United States alone. As Mexican food becomes more common in the American diet, consumers start to branch out into a more authentic presentation of Mexican food. This causes a shift in consumption from flour to corn tortillas. As the consumer demand for corn tortillas increases, food manufacturing companies are challenged with producing a tortilla that will retain its softness, pliability, foldability, and flavor while remaining safe for consumption over several months. Since tortillas have two modes of deterioration, mold and staling, there are several factors that need to be considered. Hurdle technology is employed to prevent mold growth. By adjusting water activity, pH, storage temperature, and addition of preservatives mold growth can be prevented for a period of several months. Retaining tortilla texture over time is much more complicated. Tortillas stale through a complicated process of starch retrogradation. During cooking, the starch granules gelatinize and amylose and amylopectin leech out of the granules. After the tortillas are baked, the starch immediately begins to retrograde. The amylose and amylopectin complex together form a matrix that stiffens the tortilla. Based on current research, the shelf life of a corn tortilla can be extended through a combination of CMC (0.5%), maltogenic amylase (1650 Activity Units), sorbitol (3%), glycerol (4%).

Doctor of Philosophy / Food Science Institute / Melvin C. Hunt / Three experiments were conducted to evaluate factors affecting ground beef color stability with the objectives: 1) To characterize color characteristics of different ground muscles from similarly fed and managed cows and steers; 2) To evaluate the contributions different muscles make to overall ground beef color stability; and 3) To determine if cow biological type (beef-type vs. dairy-type) affects ground beef color dynamics. In general, ground muscles from fed cows appeared darker and redder than ground muscles from steers. Chronological age did not affect ground beef color stability of muscles from fed cows. Use of steroid implants or [Beta]-agonists did not affect ground muscle color stability of fed steers or fed cows. Overall color stability varied more in muscle from steers than from fed cows. Fed cow muscles tended to have a greater proportion of saturated and mono-unsaturated fatty acids to poly-unsaturated fatty acids than fed steer muscles. Ground muscles from fed cows had better color stability properties than ground muscles from steer. When muscles of various color stability were blended to make ground beef and packaged in high-oxygen modified atmosphere (HiO[subscript]2 MAP), high color stability muscles (≥ 75%) in formulations maximizes display color life; however, inclusion of low color stability muscles (≥ 25%) in ground beef formulations had deleterious effects on ground beef color life. Ground semimembranosus (SM) from dairy cows exhibited darker initial color than ground SM from beef cows when packaged in HiO[subscript]2 MAP. However, ground SM from dairy cows was more color stable than ground SM from beef cows when packaged in HiO[subscript]2 MAP. Cow trim used as a fat source in ground beef formulations improved color stability compared to young beef trim when packaged in HiO[subscript]2 MAP. Isolating and managing muscle sources enable meat processors to better manage ground beef based upon intrinsic factors affecting ground beef color stability.

Master of Science / Department of Grain Science and Industry / Jeffrey A. Gwirtz / Variation in wheat kernel hardness is influenced by several factors including genetic expression and environmental conditions. However, these factors explain only a portion of the observed variation. Thus, there are unknown contributors to this important physical property. The following experiments investigated growing locations between farms and within the spike as a source of variation. Four commercial varieties of Hard Red Winter (HRW) wheat were chosen for evaluation; Jagger, Jagalene, Overley, and 2137. In total, 374 wheat spikes were collected from three farms participating in the Kansas State University Research and Extension- 2007 Crop Performance Tests (KSCPT). For analyses, each kernel was removed and cataloged by spikelet and floret position. A total of 10,240 kernels were uniquely identified by variety, farm, plot, spike, spikelet and floret position. Using the single kernel characterization system (SKCS), kernels were crushed to determine the hardness, diameter, weight, and moisture content. The variability of each measured attribute was greatest between spikes of a given variety. Measured attributes exist in gradients along the spike, with the top and bottom portions being most variable. This research broadens our knowledge of wheat kernel variation, and results from this experiment may contribute to improved methods for single kernel analysis.