Master of Science / Food Science Institute / Karen Schmidt / Flour is essential to bread production as it provides structure, texture, and flavor. The most common, wheat flour, is unique compared to other cereal flours as it forms gluten that is capable of forming viscoelastic dough, which retains gas produced during fermentation and helps create cohesive dough, all of which are critical to bread development. However, a certain percentage of the population has a rare autoimmune disorder, celiac disease, which is triggered by gluten. A gluten-free diet is the only remedy for celiac disease. Traditionally, in gluten-free breads, hydrocolloids, or gums have been used to mimic the behavior of gluten. However, the lack of a protein structure in breads made with hydrocolloids leads to an almost batter-like viscosity. Therefore, research has focused on gluten-free alternatives, particularly non-wheat cereal proteins that can be altered to mimic gluten’s dough forming properties. For example, zein has an average molecular weight and larger peptides than gluten, which contribute to its hydrophobic behavior. In fact, zein from maize flour is an ideal alternative as it can be manipulated to behave like gluten under certain conditions. The main difference between gluten and zein is that zein does not exhibit a large disulfide-linked polymer. Zein is also more hydrophobic than gluten. However, zein has been found to exhibit viscoelastic properties similar to gluten’s at temperatures higher than its glass transition. Other research has found the secondary structure of zein, in particular the β-sheet structure, increases at temperatures above its glass transition. This suggests that temperature and shear are not the only factors necessary to form and maintain the viscoelastic properties of zein; apparently, the β-sheet structures also affect viscoelasticity. Finally, differences such as maize variety and particle size also affect the properties of zein in bakery applications.

Master of Science / Department of Grain Science and Industry / Jeffrey A. Gwirtz / Sorghum grain is underutilized in the United States. Most sorghum flour available in the market place is whole grain flour with inferior stability and baking characteristics. The demand exists for high quality stable sorghum flour with low fiber and fat content. However, the current decortication step used for separating the bran from endosperm in sorghum milling is not economically viable and the alternatives techniques, which are based on abrasion and frictions, do poor jobs and tend to increase endosperm loss. The lack of information regarding sorghum dry milling to obtain low fat and low ash white sorghum flour is the rationale for developing a suitable flow. Previous research works in this field made some progress towards the achievement of that goal, but not enough to meet the need for high quality white sorghum flour. The main method (named F20105) developed in this study for processing sorghum (without decortication) consists of the following systems: prebreak, a gradual reduction system with purification, and an impact technology. Also, two short laboratory methods were designed for obtaining white sorghum flour for comparison purposes. These were named F20106 and F20107. The method F20106 was based on the use of Buhler Experimental Mill, a Great Western Gyratory Sieve, and Quadrumat Brabender Sr. Experimental Mill. The method F20107 was based on processing decorticated sorghum in a process which uses a hammer mill, a Great Western Gyratory Sieve and an Alpine Pin Mill. A commercial flour was evaluated along with the flours from the different methods in order to make comparisons among them. The long reduction system (FS20105) which included impact detaching techniques produced white sorghum flour with high extraction rate and good baking properties. An impact dehulling machine and a prebreak roller mill were effective in collecting glumes and cracking the sorghum kernels before first break. The shattering effect of the fragile sorghum bran was avoided by implementing air separation of bran from endosperm before each break. A purification system effectively cleaned and sorted the sorghum grits by size. Sorghum flours with different protein contents were evaluated for their baking quality properties. The protein content of sorghum flour was found strongly positive correlated with the amount of water added to the batter, cell wall thickness, cell diameter and cell volume ([rho]>0.85; P<0.0001), and strongly negative correlated with the number of cells/cm2 and L-value of the bread crust (-0.95>[rho]>-0.91; P<0.0001). It was also correlated with the a-value and b-value of the bread crust ([rho]=0.620, P< 0.014 and [rho]=0.520, P< 0.047, respectively). The diagrams F20105, F20106, and F20107 can be used successfully in their current form or with small adjustments to obtain flour from different sorghum hybrids at the laboratory scale. These diagrams also fill a gap in the currently available milling literature. Additionally they can be scaled up in the sorghum processing industry. The growing gluten-free food product market would potentially provide a rapid return on the necessary investment.

Master of Science / Food Science / Randall K. Phebus / Campylobacter is recognized as a leading cause of bacterial gastroenteritis. In the United States, Campylobacter causes an estimated 600,000 illnesses and 55 deaths each year at a cost of over $1.3 billion. It is estimated that 80 percent of Campylobacter infections are foodborne with almost 50 percent of these cases attributed to poultry. Based on these statistics, Campylobacter and poultry is considered by some to be the riskiest pathogen-food combination. Campylobacter illness is usually self-limiting but serious illness and complications can occur. Serious illness requires treatment with antibiotics, but with emerging antibiotic resistance observed in Campylobacter isolates, treatment options might be limited. Therefore, it is of importance to reduce significantly the consumer’s exposure to Campylobacter through poultry consumption. In July 2011, USDA FSIS’s new performance standard for Campylobacter in chicken and turkey slaughter establishments went into effect. For chicken, the standard allows no more than eight Campylobacter-positive samples out of a fifty-one sample set. Methods for Campylobacter detection and enumeration include direct plating using a medium such as Campy-Cefex, MPN techniques, ELISA, and PCR. To meet the new performance standard the industry will need to consider improvements in poultry production. Improvements likely will not be limited to processing interventions such as scalding, picking, evisceration, and chilling. Improvements may include on-farm interventions such as enhanced biosecurity, use of competitive exclusion or vaccinations, good hygiene practices, and improved staging at introduction to processing. Post-processing interventions that might be considered include freezing or further processing (i.e. cooking) of poultry products from Campylobacter-positive flocks. Significant improvements in establishments’ food safety programs are expected to occur to meet the standard and are predicted to result in an estimated reduction of 5,000 Campylobacter illnesses per year.

Master of Science / Department of Grain Science / Rebecca Miller / Hard winter wheat flour is predominantly used for bread production. Optimal dough handling properties are critical in commercial bread production. Variation in flour water absorption tolerance dramatically affects dough handling. Understanding the factors which affect water absorption tolerance and the influences of genotype, environment, and their interaction on those factors will improve breeding efforts and production practices to improve the quality of bread wheat. A previous study found the γ-gliadin protein fraction correlated highly with water absorption tolerance. The objectives of this study were to confirm the effect of γ-gliadin and investigate the effects of genetics and environment on water absorption tolerance. Nineteen hard winter wheat cultivars consisting of released varieties and experimental breeding lines from the Pacific Northwest grown in 2011 in 2 locations in Oregon (Pendleton and Arlington) were obtained. Quality evaluations including flour yield, test weight, kernel weight, kernel diameter, and kernel hardness were conducted on the wheat kernels and water absorption tolerance, protein content, moisture content, ash content, Solvent Retention Capacity (SRC), starch damage, and protein composition analyses were preformed on the resulting flours. The mixograph water absorption tolerance behavior of each sample was ranked as high, medium or low. Farnum and OR2080156H grown at Arlington had the highest water absorption tolerance range (1.6mL) while Farnum, Eddy, Paladin and OR2080227H grown at Pendleton exhibited the lowest interval (0.4mL). No wheat or flour parameters measured showed high correlation with water absorption tolerance. Moderate correlation was observed between water absorption tolerance and kernel weight (r = 0.39), kernel diameter (r = 0.37), starch damage (r = 0.33), and the extractable and unextractable polymeric protein fractions (r = 0.32).

Master of Science / Food Science Institute - Human Nutrition / Kadri Koppel / Pecan [Carya illinoinensis(Wangenh.) K. Koch] is a native North American nut tree that has progressed into a significant agricultural crop. Flavor characteristics were evaluated for sixteen pecan cultivars: ‘Giles’, ‘Hirschi’, ‘Maramec’, ‘Oswego’, ‘Lakota’, ‘Chetopa’, ‘Colby’, ‘Witte’, ‘Dooley’, ‘Kanza’, ‘Pawnee’, ‘Stuart’, ‘Chickasaw’, ‘Peruque’, ‘Major’, and ‘Henning’ using descriptive sensory analysis. A trained panel consisting of six panelists first developed a vocabulary for the raw pecans and scored the intensities of the samples for 20 flavor attributes. Results showed that the sixteen samples differed significantly (P ≤ 0.05) on 10 of the attributes. ‘Giles’, ‘Lakota’, and ‘Pawnee’ differed from the other 13 cultivars for the majority of the attributes. The remaining thirteen cultivars showed few differences in individual attribute ratings, but did show differences when mapped using multivariate techniques indicating as many as two clusters of pecan cultivars based on flavor. The same sixteen cultivars were then roasted and evaluated using descriptive sensory analysis by the same trained panel using the same 20 flavor attributes. Three texture attributes were also evaluated. These results were compared to the results from the raw pecans. Results showed that 4 attributes differed significantly across all cultivars when raw and roasted flavor was compared. Ten of the flavor attributes had higher intensities for the roasted pecans than for the raw pecans. Most of these attributes fell within the categories of ‘nutty’ and ‘sweet’. When pecans were roasted many flavor attributes were intensified, as compared to when they were raw. How the flavor of the sixteen cultivars changed over a 12 month period was then evaluated. Raw pecans were evaluated when fresh, at 3 months, 6 months, 9 months, and 12 months by descriptive sensory analysis. A trained six member panel evaluated four flavor attributes at all five time points. Results showed that bitter had the highest intensity scores for all 16 cultivars at all 5 time points. Rancidity increased over time and sweetness decreased over time for all attributes. The results from these studies can be used as a baseline for future pecan research.

Master of Science / Food Science Institute / Fadi Aramouni / β-(1,4)-endoxylanases, commonly referred to as xylanases, have become integral to the industrial breadmaking process. This enzyme is known to cause improvement in dough rheology, loaf volume, and crumb grain. Significant research has been conducted regarding the structure, function, and inhibition of xylanases, but there is currently no quick and reproducible method to evaluate their effect in baking. The goal of this research was to develop a quantitative method for this purpose and to determine why the effect of xylanases varies with different wheat flours. The currently used methods of test baking, dough stickiness, and spectrophotometric analysis for reducing sugars were evaluated, and failed to provide reproducible results. Therefore, a new method was developed to measure the Flour Water Expression Rate (FWER) with the addition of xylanases. Commercially available enzymes from Aspergillus niger and Bacillus subtilis were evaluated in this study. The FWER method measures the amount of water released by the xylanase over a set period of time. This method consistently provided statistically significant data (p<0.05), which was able to provide a comparison of xylanases from A. niger and B. subtilis in different flours. The results indicated that the xylanase from A. niger tends to release more water, have a higher FWER value, than the xylanase from B. subtilis. In one flour, A. niger xylanase resulted in an FWER of 15.18 compared to B. subtilis xylanase that resulted in an FWER of 9.57 at equivalent activities. However, inhibitors in the wheat appeared to cause an impact on the FWER, which was evaluated with an uninhibited xylanase from B. subtilis. This new method for the evaluation of xylanases in baking suggests varying levels of xylanase inhibitors in wheat may be the reason xylanases effect wheat flours differently.

Doctor of Philosophy / Department of Grain Science and Industry / Sajid Alavi / Sorghum grain (Sorghum bicolor) is safe for consumption by individuals afflicted with celiac disease, and its proteins can be used as a supplement in gluten-free foods. However, utilization of sorghum in human foods is limited by the poor digestibility and lack of functionality of its proteins, which result from their entrapment in protein bodies, tight association with starch, and high degree of cross-linking induced by cooking. The first part of this study presents an extensive review of current methods for concentration and isolation of sorghum proteins, which are laboratory-scale techniques used for protein characterization and have no potential for commercial scale-up. Furthermore, these methods typically use non-food grade reagents and do not improve protein digestibility and functionality. In the second part, a novel extrusion-enzyme liquefaction (EEL) process was used to produce sorghum protein concentrates to overcome the aforementioned limitations. EEL involves extrusion pre-treatment of sorghum flour and starch liquefaction with a thermostable α-amylase, followed by enzyme inactivation, protein separation and drying. To demonstrate the concept, a laboratory-scale EEL process was used to produce concentrates with higher protein content (PC; 80% db) and digestibility (D; 74%) than those made by batch liquefaction. The optimum conditions for producing concentrates with both high PC and D were 32% wb in-barrel moisture content and 2.5% α-amylase added after extrusion. Using these conditions, EEL was scaled-up to a pilot-scale process to produce sorghum protein concentrates with 72-80% db PC and 62-74% D, while the batch liquefied control had only 70% db PC and 57% D. Dynamic oscillatory measurements of dough (55% moisture) and batter (65% moisture) containing sorghum protein concentrates (5 and 10%) and potato starch were performed to evaluate protein functionality. At lower moisture, pure potato starch and dough containing 10% sorghum protein concentrate had similar elastic and viscous moduli. At higher moisture, potato starch was more stable and exhibited significantly higher moduli than the batters with protein concentrates. Sorghum protein concentrates can improve the quality of some gluten-free foods. EEL shows promise for commercial production of sorghum protein concentrates because of its high throughput and potential for delivering high protein content and digestibility.

Master of Science / Food Science Institute -- Human Nutrition / Koushik Adhikari / A significant increase in the number of products carried in supermarkets has lead manufacturers to use food color as a way to differentiate their products from competitor’s products or as a form of communication. This report’s overall objective was to review the impact of color on sensory properties of foods and beverages and help product developers understand the multiple sensory properties within a food or beverage that may potentially change by manipulating color. The effect of color on flavor or odor identification, basic taste perception, flavor or odor intensity, quality and refreshment, and consumer acceptance has been extensively researched. Research to date has shown inconsistent findings, although key themes are consistent. Some colors are more appropriate for certain foods and beverages, and product color can be directly linked to palatability. Color cues can be used for flavor identification within a food or beverage, and the presence of certain colors evoke flavor associations within a product. Perceived intensities of basic taste or flavor attributes have increased or decreased merely with color addition. Consumers use color cues to determine quality, therefore color can ultimately affect product acceptance.

Master of Science / Department of Food Science Institute / Fadi M. Aramouni / To find an optimal formulation of oil-in-water (O/W) emulsion pourable dressings containing 60% and 70% soybean oil, nine stabilizers common to the dressing industry were tested, each at three concentrations. The stabilizers tested were xanthan gum, propylene glycol alginate (PGA), a xanthan gum/guar gum/sodium alginate blend, a viscosifying modified corn starch, an emulsifying modified corn starch, microcrystalline cellulose (MCC), liquid salted egg yolks, liquid salted whole eggs, and dried egg whites (DEW). The emulsions were made with a laboratory high shear disperser and evaluated over 8 weeks by measurement of creaming in 100- mL graduated cylinders and by change in viscosity as measured by a Brookfield viscometer. The stabilizers and concentrations most effective at preventing separation and maintaining viscosity were MCC at 1%, 2%, and 3% in the 60% oil emulsion and 0.25% xanthan gum in the 70% oil emulsion. Average viscosities ranged from 3300 - 23,400 centipoise (cP). The emulsifying starch and dried egg whites were also effective at preventing creaming, but failed to maintain viscosity. The other ingredients showed some initial emulsion stability followed by either a gradual or sudden decrease in stabilization, as seen by decreasing viscosity and eventual separation.

Master of Science / Department of Food Science / Karen A. Schmidt / Milk proteins are excellent sources of sulfur-containing amino acids methionine and cysteine, in particular whey proteins. Cysteine is synthesized from methionine by γ-cystathionase. However, cysteine has to be included in the diets of certain subpopulations due to diminished γ-cystathionase activity. Cysteine, a heat- liable amino acid, may lose bioavailability during thermal processing. The objective of this research was to enhance cysteine content in yogurt while maintaining its quality. First, yogurt mixes were formulated to a total solids content of 12.5% with nonfat dry milk (NDM) (N) or a combination of NDM (10%) and whey protein isolate (WPI) (2.5%) (W), and processed at 70°C (20 min) (70) or 90°C (7 min) (90). Yogurt was prepared and maintained at 4oC for 60 days. Three replications were performed and data were analyzed using SAS®. The W mixes had 65%, 32% and 190% more cysteine, true protein and whey protein contents respectively, compared to N mixes prior to processing. However in day 1 yogurt, the highest cysteine content (398.3 mg/L) was found in the W70 yogurt and its gel quality was comparable to the N90 yogurt except for firmness. During a 60 day storage period the W70 and N90 were similar in gel quality except for firmness. Secondly, a hedonic test was done on the W70 (HC) and N90 (LC) yogurts which had been reformulated to contain sugar and vanillin. One replication was performed and data were analyzed using SAS®. The LC and HC yogurts did not vary in liking of flavor (6.1), aftertaste (6.1) and overall acceptability (6.3) corresponding to the words of “like slightly” when compared. However, the appearance of the LC yogurt was liked more than the HC yogurt (6.7 vs. 6.1) whereas the thickness of HC yogurt was liked more than the LC yogurt (6.4 vs. 5.8). These results suggest that addition of WPI along with lower process treatment resulted in yogurt with enhanced cysteine; however, further studies may be needed to optimize the WPI addition to improve the visual characteristics of the yogurt for consumer acceptance.