Master of Science / Food Science Institute / Daniel Y.C. Fung / ECA Check® Easygel® Plus (ECA) is a pectin-based gelling system that reacts with calcium ions bound to a pre-treated Petri dish, eliminating autoclaving prior to use. It can chromogenically and/or fluorogenically distinguish three organisms: Escherichia coli, Salmonella spp., and coliforms. This study compared the recovery of these organisms to conventional media using stock culture, inoculated, and non-inoculated ground beef and ground turkey. ECA was compared to Violet Red Bile Agar (VRB), Violet Red Bile Agar with 4-methylumbelliferyl-β-D-glucuronide (VRB-MUG), Xylose Lysine Desoxycholate Agar (XLD), Escherichia coli/Coliform (ECC) Count Plate Petrifilm™, and Tryptic Soy Agar (TSA). The stock culture recovery of Salmonella Typhimurium for ECA, TSA, and XLD were 8.62, 8.69, and 6.82 log CFU/ml, respectively. There was very little difference between the media in the recovery of Escherichia coli and Cronobacter spp., formerly referred to as Enterobacter sakazakii. Mean counts of presumptive E. coli in ground beef were 7.24 and 7.41 logs for ECA and VRB-MUG. Total coliform mean counts were 7.43, 7.63, and 7.37 logs for ECA, Petrifilm™, and VRB. Presumptive Salmonella means were 6.68 and 6.21 logs on ECA and XLD, while total aerobic counts were 7.84 and 6.51 logs on ECA and TSA. At 6.72 logs, ECA recovered considerably more Salmonella than XLD (5.71 logs) from the inoculated ground turkey; ECA recovered 7.62 logs total aerobic count which was significantly more than TSA at 6.89 logs. Total counts for both non-inoculated ground meats resulted in significant differences between TSA recovery and all other media. ECA also recovered significantly more than Petrifilm™ from both non-inoculated foods. The randomly selected organisms recovered from ECA were identified using BBL™ Crystal™ Enteric/Nonfermenter ID or Gram-Positive kits, and correlated precisely to the chromogenic reaction of the colonies. ECA Check® Easygel® was efficient, less labor-intensive, comparable to, and, in some instances, better than conventional media at recovering target organisms.

Master of Science / Food Science Institute- Animal Sciences and Industry / Kelly J. K. Getty / The Food and Drug Administration’s Bacteriological Analytical Manual recommends two enumeration methods for Bacillus spp.: 1) standard plating method using mannitol-egg yolk-polymyxin (MYP) agar and 2) most probable number (MPN) method with tryptic soy broth supplemented with 0.1% polymyxin sulfate. Preliminary research evaluated three inoculum preparation methods using EZ-Spore™ B. cereus pellets. Two methods involved EZ-Spore™ B. cereus pellets that were dissolved in deionized (DI) water, grown in brain heart infusion broth with manganese sulfate, and then heated to produce spores. The third inoculum preparation method of dissolving EZ-Spore™ pellets only in DI water was the most efficient due to 100% spores being present in the inoculum. Preliminary research also determined that MPN method recovered greater (p<0.05) B. cereus populations than MYP method in inoculated ultra-high temperature pasteurized skim and 2% milk. The objective of the main study was to compare the MYP and MPN method for detection and enumeration of B. cereus in raw and high-temperature-short-time pasteurized skim, 2%, and whole milk at 4 °C for 96 h. Milk samples were inoculated with B. cereus EZ-Spores™ dissolved in DI water and sampled at 0, 48, and 96 h after inoculation. No differences (p>0.05) were observed among sampling times so data was pooled for overall mean values for each treatment. The overall B. cereus population mean of pooled sampling times for MPN method (2.59 log CFU/mL) was greater (p<0.05) than MYP plating method (1.89 log CFU/mL). B. cereus populations ranged from 3.40 log CFU/mL to 2.40 log CFU/mL for inoculated milk treatments for MYP and MPN methods, which is well below the necessary level for toxin production. Even though MPN method enumerated more B. cereus, the MYP method should be used by industry for enumeration of B. cereus due to its ease of use and rapid turnover time (2 d compared to 5 d with MPN). However, MPN method should be used for validation research due to its greater populations recovered. EZ-Spore™ B. cereus pellets were found to be an acceptable spore inoculum for validation research because the inoculum consists of 100% spores and does not contain vegetative cells.

Master of Science / Food Science Institute, Animal Science and Industry / Karen A. Schmidt / Yogurt is a good source of whey proteins, which have been reported to provide positive health benefits. During yogurt manufacture, the yogurt mix receives a heat treatment which pasteurizes the product, denatures the whey proteins affecting their availability, and enhances quality attributes. Thus the objective of this research was to improve the undenatured whey protein content in yogurt. The study was divided in two parts. The first part focused on the effect of pasteurization treatments of yogurt mixes (65 °C for 30 min vs. 90 °C for 10 min) on the yogurt firmness, G’, L*, syneresis and water holding capacity (WHC), and how these properties change as a function of storage. Nonfat dry milk (NFDM) was reconstituted (~11% w/v) pasteurized, cooled, inoculated with yogurt culture, incubated to pH 4.5, stored at 5 °C ±1 and evaluated for various physical and chemical properties on days 1, 15 and 29. The experiment was replicated 3 times and data were analyzed by SAS®. Yogurt samples had a 5-fold difference in whey protein denaturation (WPD) and the greater the WPD the greater the firmness, G’, L* and WHC but lesser the syneresis. During yogurt storage, L*, G’, syneresis and WHC increased. The second part of this research focused on whey protein concentrate (WPC) addition (3%) in yogurt mix combined with two pasteurization treatments (70 °C for 30 min vs. 90 °C for 10 min) to determine their effects on the yogurt quality. Yogurt mixes were formulated using 12.5% NFDM or 9.5% NFDM and 3% WPC and a procedure similar to the previous study was followed. The WPC addition resulted in a yogurt with decreased firmness, G’, WHC but increased syneresis. Yogurt made from mixes pasteurized at 90 °C for 10 min had ~60% WPD and comparable quality attributes regardless of WPC addition. Thus, additional WPC and less WPD in this study resulted in a yogurt with slightly lesser quality attributes but more undenatured whey proteins in the final yogurt.

Master of Science / Food Science Institute - Animal Science & Industry / Fadi M. Aramouni / Smoke flavored foods continue to be a popular choice among consumers. In this study, a caramel-type flavor in whipped cream applications via Maillard reaction pathways was evaluated. A highly refined liquid smoke fraction was developed using a delignified pulp wood source, and a patented activated carbon filtration process. To maximize sensory and reactionary capabilities, a liquid smoke fraction with phenol and carbonyl concentrations of 0.07mg/ml and 12.9g/100ml, respectively, was developed. Heavy cream containing a 0.075% addition of the refined liquid smoke fraction was evaluated when reacted at 50, 63, and 72°C for 15 sec prior to chilling at 0°C for 12 h, and whipping for 8 min using a handheld mixer. Sensory analysis showed the addition of liquid smoke increased whipped cream sweetness and caramel flavors, while imparting minimal off-flavors. Probable Maillard pathways were predicted for the reaction taking place between the liquid smoke and the dairy proteins upon thermal processing. This technology can be used to develop other foods which are not traditionally smoke flavored.

Doctor of Philosophy / Department of Grain Science and Industry / X. Susan Sun / Poly(lactic acid) (PLA), a synthetic biopolymer, is a promising substitute of some petroleum-based polymers due to its mechanical and biodegradable properties. But, because of the high cost of PLA (compared to those petroleum plastics for disposable application), starch has been incorporated into PLA to reduce cost and accelerate the biodegradability rate of the composites. But, the addition of starch as filler to PLA decreased mechanical performance of the composite. The addition of methylenediphenyl diisocyanate (MDI) into PLA/starch blends improved drastically the mechanical properties of the composite. Results from thermal-degradation analysis showed that PLA had the highest Arrhenius activation energy and strongest thermal endurance of all samples, followed by PLA/starch/MDI and PLA/starch. Aged samples exposed to fluctuating humidity storage conditions significantly decreased their performance. But, storing the samples in plastic bags could minimize degradation of properties. PLA and its composites with starch would not significantly affect application function when they are stored in controlled environment. PLA and PLA/starch based composites sealed in plastic bags can be stored in fluctuating humidity conditions (30-90% RH) for up to 30 days. Tensile strength, elongation, and damping increased with average particle size of starch granules (APS). But, declination of these properties was detected with APS larger than 45 mm. Crystallinity increased as the APS decreased. Young’s modulus, storage modulus, and moisture absorption were not significantly affected by the starch APS. The use of MDI as a coupling agent altered the role of starch APS on those properties of poly(lactic acid)/starch composite. The oxidation of the primary alcohol group on C6 of starch molecules up to 10% degree of substitution did not significantly affect the mechanical properties of PLA/starch/MDI, but the composites showed a reduced inelastic deformation (tensile curve) and significant increase in storage modulus and damping. Results suggest that a substitution of hydroxyl group on C6 of starch molecules for carboxyl group (up to 10%) increased the strengthening effect of MDI enough to reduce inelastic deformation of the composites upon load, but not enough to enhance mechanical properties.

Doctor of Philosophy / Department of Grain Science and Industry / Finlay I. MacRitchie / Novel genetic materials were used to deduce gluten protein composition-functionality relationships. The Pegaso bread wheat near-isogenic lines (NILs) included addition, variation and/or deletion of major loci coding for HMW-GS, LMW-GS and gliadins. The waxy wheat lines (Svevo and N11 set) included wild, partial and complete waxy lines. Triticale translocations include 1R.1D and 1A.1D lines (GDS7, Trim, Rhino and Rigel sets) with HMW-GS 5+10 and 2+12. The main goal of the study was to establish the usefulness of NILs as appropriate materials to investigate the structure-function relationships of wheat proteins and to evaluate the performance of unique triticale translocations and waxy wheat lines. Effect of genetic variation on phytochemical (phenolic acid and policosanol) contents was also studied. Innovative methods like MALLS, Lab-on-a-chip and micro (10 g) baking were utilized along with traditional analytical methods. Results confirmed the potential of using NILs in understanding the effects of certain proteins coded at specific loci that might often be targeted in breeding programs. Removal of expected chain terminators at Gli-1/Gli-2 loci causes a shift in MWD to higher values, reflected in higher UPP and dough strength. Lines with HMW-GS 5+10 were clearly separated from 2+12 lines in terms of dough strength and UPP. The present study obtained evidence that modified ω-gliadins acts as chain terminators and cause reduction of protein polymer size and thus shifts in MWD. Marked differences in terms of milling characteristics, protein composition and ultimately in end-use functionality were observed with various waxy wheat null lines. Loaf volumes with waxy wheat flour alone were higher than a 50% blend with commercial wheat; however, breads were unacceptable to consumers in all aspects. Poor milling quality, very low mixing times with low bread loaf volumes were typical of all the triticales studied. However, translocation of the HMW-GS from wheat chromosome 1D increased dough strength, particularly the HMW-GS 5+10. Among the phytochemicals studied, double nulls at Gli-1 loci of Pegaso NILs had the highest total policosanols and total phenolic acid contents.Slight variation to wheat phenolic acid composition and contents were observed with waxy wheat and triticale lines.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Channa B. Rajashekar / Studies were conducted to examine the role of antioxidants in adaptation of lettuce (Lactuca sativa L.) to unprotected environmental conditions and various environmental stresses. Antioxidants, in addition to being a plant defense mechanism, are phytochemicals that provide significant health-promoting and nutritive value in human diet. Various approaches involving mild environmental stresses and cultural and management practices have been used to enhance the quality of this commonly consumed leafy vegetable by improving its phytochemical and health-promoting attributes. Lettuce plants grown in protective environments adapt to unprotective environmental conditions by activating antioxidant genes such as phenylalanine ammonia-lyase (PAL), gamma-tocopherol methyl transferase (gamma-TMT), and L-galactose dehydrogenase (L-GalDH) involved in the biosynthesis of phenolic compounds,alpha-tocopherol and ascorbic acid, respectively. Mild environmental stresses such as heat shock, chilling, water stress and high light also activate these genes leading to the accumulation of secondary metabolites and phytochemicals without any adverse effect on biomass accumulation. The phytochemicals included chlorogenic acid, chicoric acid, caffeic acid, quercetin-3-O-glucoside and luteolin-7-O-glucoside. However, under field conditions, application of drought stress did not produce consistent results with regard to the phytochemical composition of lettuce. Plants grown in open field have higher phenolic content and higher antioxidant capacity than those grown in high tunnel. However, these plants also had less biomass accumulation. Many factors such as plant age, variety, fertilization, transplanting shock affected the phytochemical composition of lettuce. The red leaf variety 'Red Sails' had higher antioxidant capacity than 'Baronet' and younger plants had the highest phytochemical content. With regard to the management practices, there was no significant difference in phytochemical composition between organically and conventionally managed crops. Also, low fertility favored the accumulation of phytochemicals and increased the antioxidant capacity. Thus, the results show that mild environmental stresses along with appropriate cultural and management practices can enhance the quality of lettuce by improving their phytochemical composition.

Master of Science / Food Science Institute / Delores H. Chambers / The challenge with reduced sodium foods is finding a suitable sodium replacement that delivers a salty flavor without extraneous off flavors. Potassium chloride (KCl), a commonly used salt replacer, when used in conjunction with sodium chloride, can be perceived as salty; however to some people, KCl tastes bitter or metallic. The hypothesis for this research was the belief that a majority of people do not describe the flavors associated with KCl as bitter, metallic, or other possible negative terms. The objectives were 1) To determine the impact of KCl addition on the saltiness, bitterness, and other sensory characteristics in model soup systems using a trained descriptive analysis panel and 2) To determine what words are most frequently chosen by consumers to describe flavors associated with KCl. There were two studies conducted; 1) The first study examined the basic taste intensities in samples with varying levels (19%-41%) of total sodium ions and samples with a set total sodium ion level (19%) and varying levels of KCl (0%-0.75%) in model soup systems in order to understand the potential interaction of KCl on the perceived saltiness of NaCl. The degree to which KCl can be used in reducing total sodium ion levels without adversely affecting the basic taste sensory properties was also examined. Panelists evaluated the samples using the Sensory Spectrum® method. Salt, sour, bitter, umami, and metallic attributes were rated for chicken broth. Salt, sweet, sour, and bitter attributes were rated for tomato soup. 2) The second study examined the consumer language used to describe the flavors associated with KCl when used in a reduced sodium model soup system. Focus group participants generated the initial list of flavor descriptors for high (0.75%) KCl levels in chicken broth. A larger consumer study was conducted with subjects pre-screened for sensitivity to KCl Consumers were given reduced sodium chicken broth or tomato soup without KCl and another sample with 0.45% KCl, labelled Flavor A. Subjects then chose all of the descriptors from a pre-selected list that describe Flavor A, the flavors associated with KCl. Comparisons in language descriptor selection were made among ethnic groups (African American, Hispanic, Caucasian, and Asian), gender, and age groups. As an example, among ethnic groups, for chicken broth, Hispanics chose the salty descriptor less frequently than the other ethnic groups, whereas Asians chose the salty descriptor more frequently than the other ethnic groups. The trained descriptive analysis panel did not find an increase in bitterness perception as KCl levels increased. Consumers frequently selected characterizing flavor terms to describe flavors associated with KCl and rarely selected bitterness, metallic or other potentially negative terms to describe KCl flavor. The significance of these findings is that there may be a higher potential for sodium reduction in the food industry using KCl as a sodium ion replacer.

Master of Agribusiness / Department of Agricultural Economics / Ted C. Schroeder / For the industry to be able to produce a higher performing and consistent quality product, evaluation of performance and information needs to be collected and available for producers to make more informed beef cattle production management decisions. In recent history, the cattle industry has taken on the complex job of maintaining and recording performance records through programs and efforts such as breed association data bases, and herd health data bases. The constant evaluation of performance and genetic records has supplied producers with data resulting in performance, maternal and carcass statistical records such as Expected Progeny Differences (EPDs). Additionally, developing technology is helping the industry through selection and decision tools such as Carcass DNA marker identification. This study evaluates how the selection tools of EPDs and DNA affect the value of Gelbvieh / Balancer bulls at auction. Data collected for this study is from various Gelbvieh / Balancer bull sales throughout Nebraska in the spring of 2008. Variables evaluated in the study were data and information provided to potential buyers before the auctions to be able to observe how this information affected the value of the purchased bull for each buyer. Variables evaluated were Igenity Profile Carcass DNA values of Ribeye Area, Marbling, and Tenderness. Additionally, Performance EPDs of Calving Ease Direct, Birth Weight, Weaning Weight, Yearling Weight, Ribeye Area, and Marbling were evaluated. The only actual measurement observed was Scrotal Circumference. The hedonic models developed for this study suggest that the selected bull data provided to potential buyers before sale are not the only significant determinants affecting price. Statistical measurements and technologies developing the industry are having a profound and positive effect on production and as selection tools however, are not the only potential variables affecting the value of a sire at auction. Other possible variables effecting auction value can also include evaluation of phenotype, pedigree, and buyer benefits. The data and variables evaluated in the study should still be used as valuable additions to other selection tools and observations when selecting a future beef sire.

Doctor of Philosophy / Department of Hospitality Management and Dietetics / Elizabeth B. Barrett / The primary purposes of this research were to 1) use the Theory of Planned Behavior (TPB)to assess Millennial generation wine consumers attitudes, perceived behavioral controls, and subjective norms related to purchasing wine in casual dining restaurants (CDR), and 2) use Conjoint Analysis (CA) to analyze Millennials’ preferences for wine information on the restaurant menu. An instrument was designed based on the TPB and CA and was sent online to 216 consumers using the database of a market research firm (e-rewards). Independent variables (attitude, perceived behavioral control, and subjective norms) were analyzed to predict behavioral intentions to purchase wine. Principal component analysis was combined with multiple linear regression to assess intention. Results identified attitudes and subjective norms as being significant in predicting behavioral intention, perceived behavioral controls was partially significant. Millennial’s believe ordering wine with their friends and family in casual dining restaurants will make them feel smart and sophisticated and will increase the enjoyment of food. However, they do not believe wine consumption is appropriate in CDR’s; they had strong perceptions that wine is purchased for special occasions and consumed in fine dining restaurants. Part II of the study employed conjoint analysis to determine Millennials preferences for wine information on the menu. Results indicated that Millennials prefer menus that provide wine/food pairing information, wine flavor descriptors located near food listings and quality wines at an affordable price. Millennials attitudes, subjective norms, and perceived behavioral controls support previous research that this generation is interested in wine and wine is a social experience that increases their enjoyment of food and time spent with their friends and family. Through the use of CA, the present study suggests wine information on the menu is important to this segment of consumers. Additional research should be conducted to understand the stereotypes this generation has about wine consumption in casual dining restaurants. These operators and owners should consider focusing their marketing efforts showing Millennials enjoying wine while celebrating special occasions with their friends and family. In addition, redeveloping menus in their operations to add wine information may increase interest in wine and generate profit.