Rice is the leading staple for half the world’s population. Climate change, expanding populations and loss of agricultural land are projected to reduce rice yields by upwards of 30%. Significantly, rice yields decline by 10% for every 1°C increase in temperature. Temperatures ≥ 32°C can cause failure in male reproductive development and eliminate yields in some cultivars. This dissertation determined the developmental features and mechanisms associated with failure in male reproduction at temperatures of 32 °C and 36 °C in temperature tolerant and sensitive cultivars of O. sativa and O. glaberrima. Temperatures of 32 °C impaired anther dehiscence in the temperature sensitive cultivar of O. sativa by preventing septum cell wall degradation, which is essential for pollen dispersal. Temperatures of 36 °C induced abortion in pollen development either during meiosis primarily in O. sativa or at the uninucleate stage in O. glaberrima. Abortion during meiosis was associated with autophagic programmed cell death, whereas failure at the uninucleate stage of pollen development was associated with features of necrosis such as cytoplasmic shrinkage and cell wall collapse. Increased hydrogen peroxide production was detected in aborting meiocytes and uninucleate microspores at 36 °C, indicating that this reactive oxygen species may contribute to the failure of male reproductive development in rice during high temperature stress. Identification of the timing of failure in male reproductive development, and the cellular features associated with these processes in rice, form the basis for the identification of molecular mechanisms that control yield responses to high temperature stress.

Rice is the leading staple for half the world’s population. Climate change, expanding populations and loss of agricultural land are projected to reduce rice yields by upwards of 30%. Significantly, rice yields decline by 10% for every 1°C increase in temperature. Temperatures ≥ 32°C can cause failure in male reproductive development and eliminate yields in some cultivars. This dissertation determined the developmental features and mechanisms associated with failure in male reproduction at temperatures of 32 °C and 36 °C in temperature tolerant and sensitive cultivars of O. sativa and O. glaberrima. Temperatures of 32 °C impaired anther dehiscence in the temperature sensitive cultivar of O. sativa by preventing septum cell wall degradation, which is essential for pollen dispersal. Temperatures of 36 °C induced abortion in pollen development either during meiosis primarily in O. sativa or at the uninucleate stage in O. glaberrima. Abortion during meiosis was associated with autophagic programmed cell death, whereas failure at the uninucleate stage of pollen development was associated with features of necrosis such as cytoplasmic shrinkage and cell wall collapse. Increased hydrogen peroxide production was detected in aborting meiocytes and uninucleate microspores at 36 °C, indicating that this reactive oxygen species may contribute to the failure of male reproductive development in rice during high temperature stress. Identification of the timing of failure in male reproductive development, and the cellular features associated with these processes in rice, form the basis for the identification of molecular mechanisms that control yield responses to high temperature stress.

Master of Science / Food Science Institute / J. Scott Smith / Acrylamide is a naturally occurring compound that is formed during the Maillard reaction. The International Agency for Research on Cancer has classified acrylamide as a “probable human carcinogen” as a result of tumor development in laboratory animals when acrylamide is ingested in high concentrations. The amino acid asparagine is particularly important in the formation of acrylamide due to its structural significance; its structure is analogous to that of acrylamide. Potato tubers contain high amounts of asparagine, thus food products such as French fries and potato chips (crisps) have been flagged for their high acrylamide levels and widespread consumption. Acrylamide mitigation in potato products can take place either during raw variety selection (or breeding) or during processing. Heating potatoes at a lower temperature or for a shorter time has shown to significantly decrease acrylamide levels. Numerous studies have shown that use of acidulants, preservatives, and low pH conditions dramatically reduce acrylamide formation by protonation of the asparagine molecule. Hydrolysis and epimerization of sugars during storage, precursor concentrations, and plant physiology are agronomic factors that can be manipulated to decrease acrylamide concentrations. Asparagine has shown to be the rate limiting factor in acrylamide formation, so processing potato cultivars with low asparagine concentrations will result in lower acrylamide levels in the finished product. Continued research areas are focusing on cultivar studies and process optimization to provide a product with lower acrylamide levels but the same sensorial attributes as current products.

Doctor of Philosophy / Department of Grain Science and Industry / Sajid Alavi / Extrusion processing is a technology widely used to make ready-to-eat snack and breakfast cereal products. The raw materials that result in optimal texture and consumer acceptance are mainly those with high levels of starch, which greatly limits the nutritional value of these products. One alternative to enhance the nutritional value is the incorporation of fruits and vegetables. Fruits and vegetables are consistently under-consumed by the American population and incorporation into extruded products may help increase the intake of important nutrients, such as dietary fiber. In the first part of this study a lab-scale twin screw extruder was used for processing directly expanded products based on corn flour and apple pomace (0-28%), resulting in a total dietary fiber content of 1.1-22.5%. Apple pomace increased nucleation and favored axial expansion. The change in cell size and alignment explained the higher mechanical resistance caused by apple pomace. The objective of the second part was to study the effect of preconditioning regimen on the extent of matrix transformation and impact on texture, microstructure and digestibility. The material was processed on a pilot scale extruder. The results showed that increasing the opportunity for hydration increased starch gelatinization at all pomace levels. Apple pomace promoted milder extrusion conditions, resulting in less starch gelatinization and solubilization and reduced starch digestibility. Digestibility was also affected by structure, with a strong correlation between the available starch fraction and cell wall thickness/cell size ratio (r=0.90). The third part of this study was designed to gain a better understanding of the impact of the individual cell wall components (cellulose, lignin, xyloglucan and pectin) on expansion and structure formation. The results suggest that compatibility with starch is critical for good dispersion in the matrix, therefore good expansion and structure forming properties.

Doctor of Philosophy / Department of Human Nutrition / Koushik Adhikari / Coffee is the most consumed beverage after water and the second widely traded commodity after crude oil. In the past decade or so the market for coffee has exploded. It is no longer competitive for the coffee industry to offer consumers just a ‘good’ cup of coffee. Coffee is mainly consumed for enjoyment and offers consumers the desirable emotional experience. Currently not much work has been done to capture the emotion experiences elicited by coffee drinking, which led to our objective: to identify and assess the feelings that are stimulated by the coffee drinking experience through the development of an emotion lexicon. In the first part of the study, focus groups were utilized to generate and fine-tune a list of emotions that occur during the coffee drinking experience. The list of terms was further refined by check-all-that-apply method, resulting in 86 emotions, which included 39 terms from a recently published emotion lexicon for food. In the second part of the study, this lexicon of 86 emotions was used to evaluate six coffee samples of various origins and degrees of roasting with 94 consumers. The emotion intensities before and during drinking were assessed. Consumers were clustered into six clusters based on the acceptability scores, and the appropriate emotions for distinguishing the coffee samples were determined by Stepwise Regression Analysis, which resulted in 44 emotions. Emotion maps for each consumer cluster constructed using Principal Components Analysis revealed that each sample generated distinctive emotional responses, which varied across each cluster. The last part focused on identifying the sensory drivers of emotions to understand the consumer’s perceptions because emotional and sensory experiences determine acceptability and consumption of coffee. Two separate highly-trained panels (a general panel and a coffee panel) performed descriptive analysis of the six coffee samples. After comparing the two panels, the coffee-specific panel data was used to identify the sensory attributes that might be responsible for eliciting certain emotions in the consumers. For instance, darker roasts seem to elicit positive-high energy emotions. Overall, this study is a stepping stone for more in-depth product-specific emotion studies in future.

Master of Science / Department: Food Science / J. Scott Smith / Non-nutritive sweeteners are alternative sweeteners that provide the taste of sweetness without a caloric contribution. In this Florence’s HomeStyle Cha-Cha study, aspartame, acesulfame K, sodium saccharin, and neotame were evaluated as a substitute for sucrose in the formulation. These sweeteners were used at their recommended equivalency levels to match the sweetness potency level to that of sucrose. Because they are more potent than sucrose, minimum amounts were needed to replace sucrose, and the remaining amounts were filled with maltodextrin. Using maltodextrin as bulk filler is common practice in the industry when replacing sucrose with a non-nutritive sweetener. This study evaluated the quality of the finished product in determining which non-nutritive sweetener had similar taste, aroma, and density qualities as the control, which was Cha-Cha sweetened with sucrose. The results of the evaluations indicated that Cha-Cha sweetened with acesulfame K was more similar to the control than the other non-nutritive sweeteners. Of the three taste characteristics evaluated for their degree of intensity, sweetness, saltiness, and bitterness, the acesulfame K sweetened treatment was closer to the control. In the GC/MS analysis in characterizing the volatile aroma compounds, acesulfame K contained all the aroma compounds with smaller differences in concentration than the other experimental treatments. In the density evaluation, the experimental treatments were similar to the control treatment. In conclusion, Florence’s HomeStyle Cha-Cha sweetened with acesulfame K is similar in quality to the sucrose-sweetened control.

Master of Science / Food Science Institute / James L. Marsden / Consumers demand for high quality, natural and fresh tasting food, free from preservatives and additives, with a clean label and an extended shelf life has increased. High pressure processing (HPP), also known as high hydrostatic pressure, is a non-thermal food preservation technique that has the potential to meet these demands. It is an opportunity to preserve food, by applying intensive pressure in the range of 300-900 MPa, without adversely affecting organoleptic, textural and nutritional qualities as thermal processing like pasteurization and sterilization may do. In a typical high pressure batch cycle, the food prepackaged in a high-barrier flexible pouch or a plastic container is loaded into a perforated basket that goes into the pressure vessel; the pressure is then increased to the processing target pressure (come-up time); the product is held at the desired pressure for 3 to 10 minutes (pressure holding time); after which the pressure is released in usually few seconds (decompression time) and the product can be unloaded at this point. The pressure is applied uniformly in all directions simultaneously and this is known as isostatic pressure. Pressurization is usually accompanied by a moderate and uniform temperature increase called adiabatic heating. However, the food product usually rapidly returns to its initial temperature at decompression. With the recent shift in consumer lifestyle toward healthy living and healthier food, the consumption of raw fruits and vegetables has increased in popularity. However, as per the Centers of Disease Control and Prevention, fruits and vegetables have recently been associated with multiple foodborne disease outbreaks; the effect of high pressure processing on microbial safety, quality and sensory characteristics of fruits and vegetables has therefore been widely investigated as an alternative to traditional food processing and preservation methods. HPP inactivates microorganisms and quality-deteriorating enzymes and has limited effects on covalent bonds resulting in minimal modifications of food-quality attributes such as color, flavor and nutritional values. However, depending on the fruit or vegetable, high pressure could induce chemical or biochemical reactions that can affect their quality attributes.

Master of Science / Department of Food Science / Doug Powell / In the development of a hypothetical new food product (Beta Buzz) a company must have a thorough understanding of the associated food safety risks, and control factors needed to protect their consumers and their brand. The company must understand each of the suppliers, and take a proactive approach in determining the supplier requirements. It is critical that manufacturing risks be controlled and/or reduced through a combination of internal program compliance, government regulations, third party audit compliance, and/or customer audits and expectations with a focus on ingredients, the finished product and the manufacturing process itself. Food consumers have a right to safe food; the industry, as well as the government, has a responsibility to ensure consumers receive safe food.

Master of Science / Department of Food Science / J. Scott Smith / Heterocyclic amines (HCAs) formed during cooking of meats at high temperatures are suspected cancer causing compounds and efforts have been made to reduce their levels. Spices possessing high levels of antioxidants have been shown to inhibit these compounds when incorporated prior to cooking. Seven spices, black pepper, rosemary, turmeric, thyme, cinnamon, ginger and oregano were analyzed for their antioxidant capacity using three different assays. These spices were individually added at 0.25% to beef patties fried at 400 °F for 5 min per side to evaluate their effect on HCA inhibition. Black pepper was emphasized in this study by studying the effect of addition at different concentrations (0.25, 0.50, 1.00 %) on HCA reduction. It was found that patties treated with black pepper individually, as well in combination with other spices, greatly decreased the formation of HCAs. Black pepper at 0.25% level showed the highest inhibition of PhIP levels (85%). The spices were shown to have high levels of free radical scavenging activity as measured by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Overall, black pepper had significantly lower DPPH scavenging activity but still showed high HCA inhibition. All the spices individually inhibited HCA by 55-82%. Black pepper in combination with turmeric was the best combination, showing a 94.74% inhibition of HCA formation.

Master of Science / Department of Food Science / J. Scott Smith / The prevalence of diabetes along with the perceived impact of sugar on health in general has increased the demand for reduced-sugar and sugar-free baked products. Cakes typically contain large quantities of sucrose which affects not only flavor but also color, volume, and texture. This study evaluated the effect of replacing sucrose in white layer cakes with polydextrose and two artificial sweeteners: sucralose and stevia extract. White layer cakes were made using AACCI Method 10-90.01. Batter properties were evaluated by measuring specific gravity. Volume index was measured using a cake template (AACCI Method 10-91.01). Slice area, number of cells, number of holes, and wall thickness of the crumb were calculated and recorded using C-Cell Cake Imaging system. Control batter made with 135% water had a specific gravity of 0.90 g/cc and a cake volume index of 112. The cakes had a nicely golden brown, shiny surface. The crumb grain was fine with an even cell distribution. Optimum water level and baking time were obtained for each cake variation. Although replacing sucrose with polydextrose had no significant effect on specific gravity (p>0.05), a 25% replacement resulted in a cake with a volume index of 110, 50% with an index of 105, 75% with an index of 103, and 100% with an index of 97. The crumb grain was similar to the control cake. Adding sucralose and stevia yielded similar results, where lower volumes were recorded as polydextrose and sucralose/stevia were increased in the cake formula. Complete replacement of sucrose with polydextrose and sucralose or polydextrose and stevia produced an acceptable volume of cake. The number of holes and wall thickness of the crumb was not significantly different in any cake variation. Therefore, polydextrose and both sucralose and stevia are suitable as sucrose replacers in cakes. Key indexing terms: cakes, polydextrose, stevia, sucralose.