Browsing by Subject "Food Science"

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Concentration and extraction of Bacillus anthracis spores and ricin.
(2009-06) Leishman, Oriana Nicole
Food is an essential part of life for every human and animal. In order to feed the world, food production has become a global industry. This globalization brings efficiency of production, transportation, and year round availability of many ingredients. However, mass production of food also means that any mistake made during production is magnified in scale and distribution. Recent incidents of food contamination have involved not only traditional food pathogens, such as Salmonella and Escherichia coli O157, but also have included chemical contaminants such as melamine. These incidents serve to highlight the inherent vulnerability of food to contamination. Although the majority of foodborne illnesses are caused by a small group of pathogens, this does not preclude other bacteria or agents from being transmitted through food sources. Many potential bioterrorist agents have also the potential to be transmissible through food and water sources. Some of these agents, such as Bacillus anthracis spores and ricin toxin, are also resistant to the effects of existing food processing technologies such as pasteurization. Given the inherent vulnerability of the food production system, it seems a likely target for potential bioterrorism attack. Many rapid and sensitive tests have been developed to detect biological agents in a variety of settings. However, the complex nature of food matrices often limits the application of these tests to food sources. In addition, the distribution of a select agent in a food source may not be homogeneous, and testing of small samples may not represent the whole batch. The goal of this project was to design and test pre-analytical extraction techniques for two potential bioterrorism agents, B. anthracis spores and ricin toxin, from liquid foods. The outcome of this project was the development of a rapid concentration and extraction protocol for milk and fruit juice potentially contaminated with B. anthracis spores. The resulting sample was compatible with detection via real-time PCR for both milk and fruit juice samples and juice samples were compatible with detection with a commercially available lateral flow immunoassay. This concentration and extraction procedure enhanced the limit of detection by 2 log CFU/ml spores, such that real-time PCR can consistently detect B. anthracis at a level of 10 spores/mL in the initial sample. This project also examined the application of immunomagnetic separation for extraction of ricin toxin from liquids. Results from this portion of the project suggested that immunomagnetic beads can specifically bind ricin in traditional immunomagnetic separation. However, recirculating immunomagnetic separation using the Pathatrix® system was not demonstrated to specifically bind ricin.
Control of enterohemorrhagic Escherichia coli using bacteriophages
(2010-07) Viazis, Stelios
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 has been recognized as a major foodborne pathogen responsible for frequent gastroenteritis outbreaks. Phages can be used as a natural antimicrobial method to reduce bacterial pathogens from the food supply. The objective of the first study was to isolate, identify and characterize a diverse collection of lytic bacteriophages capable of infecting EHEC serotypes O26, O111, and O157. Phages were isolated from dairy and feedlot manure using EHEC O157, O26, and O111 strains as hosts. Plaques were purified and screened against additional strains (14, O157; 10, O26; 10, O111) using the efficiency of plating method (EOP). Phage CEV2 and five other phages previously isolated were able to lyse all 14 O157 EHEC strains with EOP values consistently above 0.001. Two phages isolated from fecal slurry from dairy and feedlot cattle were highly effective against strains of E. coli O157, through EOP tests, and against O26 through spot tests, but not O111. Bacterial challenges against high titers of four E. coli O157 strains suggested that a mixture of the 8 most effective phages was just as effective as or more than each individual phage. This collection of phages can be grouped and potentially used as an antimicrobial cocktail to inactivate O157 and O26 serotypes. The objective of the second study was to determine the effect of the bacteriophage cocktail, BEC8, on the viability of a mixture of EHEC O157:H7 strains applied on surfaces of materials representative of food processing plants. Sterile stainless steel chips (SSC), ceramic tile chips (CTC), and high density polyethylene chips (HDPEC) were used. The EHEC O157:H7 strains used were EK27, ATCC 43895, and 472. Exponentially growing cells from tryptic soy (TS) broth cultures were spot inoculated on surfaces and dried. EHEC cells were placed at high, medium, and low inoculum levels (10 6 , 10 5 , and 10 4 CFU/mL, respectively). Appropriate controls and BEC8 (approx. 106 PFU/mL) were applied on treated surfaces. The surfaces were incubated at 4, 12, room temperature (RT), and 37°C. EHEC survival was determined using standard plate count on TS agar. No survivors were detected after BEC8 treatment at a low inoculum level at the following incubation conditions: 37oC for 10 min and RT after 1 h on SSC and CTC; 12°C after 10 min on SSC, 1 h for CTC, and 24 h for HDPEC. These results indicated that the phage cocktail was effective within an hour against low levels of the EHEC mixture at RT on all 3 hard surfaces. The objective of the third study was to determine the effect of the bacteriophage cocktail, BEC8, on its own and in combination with the essential oil trans -cinnameldehyde (TC) on the viability of a mixture of EHEC O157:H7 strains applied on baby romaine lettuce and baby spinach leaves. The EHEC O157:H7 strains used were nalidixic acid resistance mutants of EK27, ATCC 43895, and 472. The methods used were similar to the second study. The leaves were incubated at 4, 8, RT, and 37oC in Petri dishes with moistened filter papers. EHEC survival was determined using standard plate count on nalidixic acid containing Sorbitol MacConkey agar. No survivors were detected when treated with BEC8 or TC separately at low inoculum level after 24 h at RT on lettuce and spinach. However, when the EHEC inoculum size and/or incubation temperature increased, the efficacy of BEC8 and TC decreased. When the two treatments were combined, no survivors were detected after 10 min at all temperatures on lettuce and spinach. These results indicated that the phage cocktail and TC combination was highly effective against EHEC on leafy greens.
The creation and testing of a scale to measure the subjective experiences of hunger and satiety.
(2011-07) Karalus, Melinda B.
The objective of this research was to develop and test a questionnaire to assess satiety sensations. Factor analysis of satiety related questions revealed five factors: mental hunger, physical hunger, mental fullness, physical fullness and food liking. In the first validation study, thirty participants evaluated satiety feelings produced by oranges and oatmeal at 0min, 60min and 120min after consumption. Food intake from an ad libitum snack offered two hours after breakfast was covertly recorded. The factor scales and traditional single-item scales (hunger, fullness, desire, and prospective consumption) revealed that oatmeal was more satiating than oranges. The factor scales offered enhanced understanding over the traditional scales by showing that oranges produced much more mental hunger and slightly more physical hunger than the oatmeal. The factor scales also had smaller distributions around the means and greater effect sizes than the traditional scales indicating a greater sensitivity to the differences between the oranges and the oatmeal. In a second study, participants evaluated satiety feelings produced by two equal-calorie smoothies that differed only in that one contained cumin to lower acceptability. The more palatable regular smoothie provided greater mental fullness factor sensations than the spiced cumin smoothie. Again, all of the factor scales produced smaller distributions around the means and greater effect sizes. In a third validation study, hunger and satiety of oligofructose, inulin, soluble corn fiber, resistant wheat starch and a control with no added fiber in chocolate crisp bars was evaluated. Food intake was measured at an ad libitum lunch served 180min after breakfast and subjects recorded food intake over the remainder of the 24hr study day. Breath hydrogen and methane and GI tolerance were assessed. While there were no significant differences in hunger or satiety found using the traditional scales or factor scales among the fiber treatment bars, the factor scales exhibited the least amount of variability with smaller standard deviations around the means. The oligofructose bar produced the greatest amount of breath hydrogen, bloating and flatulence ratings while the control bar produced the least. The multi-item hunger and fullness factor scales offer enhanced sensitivity and understanding of satiety produced by foods.
Development and application of a methodology to determine different ferulic acid populations in cereals and cereal based products.
(2012-01) Vaidyanathan, Sharmila
Abstract summary not available
Effects of bitterness, roughness, PROP taster status, and Fungiform papillae density on bread acceptance.
(2010-02) Bakke, Alyssa Joy
Consumption of whole grain foods, including whole wheat bread, has been linked to reduced risk of coronary heart disease, type II diabetes, certain cancers, and all cause mortality, but consumption falls far below recommended levels. Conventional wisdom dictates that refined bread is better liked than whole wheat bread, but support for this contention is scarce. If refined bread is preferred to whole wheat bread, determining the specific attributes or consumer characteristics that contribute to the disliking of whole wheat bread would provide food processors with the knowledge needed to develop technologies to improve the acceptability of whole wheat bread and to test acceptance of these products with consumers. In phase one of this study, we examined consumer preferences for refined and whole wheat breads. In phase two, we examined how two consumer characteristics, sensitivity to 6-n-propylthiouracil (PROP) and fungiform papillae density, affected perception of bitterness and roughness, two attributes that may contribute to whole wheat bread dislike. In phase three, we examined how three sensory properties, bitterness, roughness, and color and three consumer characteristics, bread type preference (whole or refined), perceived PROP intensity, and fungiform papillae density, affect bread liking.
Effects of Pasteurization Method on Lactose
(2012-04-18) Daninger, Erin
In response to claims that lactose-intolerant people were able to drink milk pasteurized utilizing the low temperature, long time method, it was decided to conduct a study comparing the lactose levels in milk pasteurized with two different methods: low temperature, long time (145 degrees F for 30 minutes) and high temperature, short time (165 degrees F for 15 seconds). It was hypothesized that there would be higher available lactose levels in the milk pasteurized with high temperature, short time method. Milk from Autumnwood Farm, a local creamery that pasteurizes with the low temperature, long time method, was used. Raw milk was also collected at the same time and pasteurized in small batches at the high temperature, short time method requirements. Milk samples were analyzed with a colorimeter to determine if browning was evident. After sample clean up and Megazyme Lactose and D-Galactose kit preparation, the lactose and D-galactose levels were determined with a spectrometer. Samples were prepared and run through high-performance liquid chromatography. First round results showed minimal differences with the colorimeter; varying largely based on homogenization rather than pasteurization. Spectrometer and HPLC results did not show differences in lactose concentrations in the various samples. Further research will be conducted to see if there are differences in milk protein, to see if the Maillard reaction has changes on the lactose.
Effects of various emulsifying salt concentrations and cheese types in reduced sodium process cheese
(2012-04-18) Saputra, Ern
Process cheese is manufactured by blending continuously and heating one or more types of natural cheese in the presence of emulsifying salts and other nondairy ingredients to form a homogenous plastic mass. Although the process produces a product with extended shelf life and numerous enduse applications, the sodium content of the final product also increases. Therefore, process cheese is used in a wide variety of food products, widely consumed and often contribute to hypertension and other related disease. The objective of this research was to reduce the sodium content in process cheese and to examine the textural properties as well as consumers’ acceptance on reduced sodium process cheese. Four different treatments of process cheeses were manufactured at different sodium level (full sodium control, 18%, 26% and 44% reduction of sodium) using a Thermomix TM 31, a food blender and processer. The samples were then tested for their chemical components. The textural characteristics of the process cheese were analyzed by Texture Profile Analysis (TPA) and meltability test and also surveyed for consumer acceptance and sensory perception. The chemical components of all the different treatments were similar and did not contribute significantly to the texture and meltability of process cheese. TPA results showed that the full sodium control and 18% sodium reduction gives more firmness to the cheese as their average hardness were greater than the 26% and 44% sodium reduction. Meltability test showed that as the 26% and 44% reduction of sodium produced cheese with higher meltability than the full sodium control and 18% sodium reduction. Sensory analysis also showed that as the amount of sodium in cheese was reduced, the resulting products were less firm and the amount of work required to chew the process cheese was less. Sensory results showed that the saltiness level of the 44% sodium reduction was the highest and the full sodium control was the lowest. The sensory panelists failed to notice the difference in saltiness as the sodium content in process cheese was reduced. It also showed that highest value of off-flavors increases as the percentage of sodium reduction is higher.
The evaluation of silica based self-assembling matrices for flavor encapsulation
(2008-12) Krishnan, Savitha
The primary objective of this research was to comprehensively evaluate the applicability and utility of alkyl modified silica matrices for flavor encapsulation. These silicate matrices were generated through a sol-gel process by co-hydrolyzing and co-polymerizing a simple alkoxysilane and a long chain alkylalkoxysilane. In the first study, a response surface model was designed to determine the statistically significant variables of the sol-gel process on the encapsulation efficiency of a hydrophobic flavor molecule (limonene). In Study 2 and 3, two formulations that exhibited the highest encapsulation efficiency from Study 1 were employed to encapsulate a complex flavor mixture consisting of compounds (diacetyl, methyl propanal, methyl pyrrole and damascenone) having a wide range of physicochemical properties. As the losses of flavor compounds in silicate matrices were high during drying, the matrices were blended with an emulsifying starch before freeze drying. Flavor mixture consisting of compounds was incorporated into medium chain triglycerides (MCT's), limonene and neat before being added into the carrier matrix. We examined the efficacy of these proposed matrices by conducting a comprehensive evaluation of the stability of encapsulated flavor compounds in silica: starch blends during storage and examining the release profiles of these compounds in a food application. While hydrophilic silica blends outperformed the hybrid silica blends in the absence of the solvent, the latter performed better in the presence of solvents. Further, the differences in release properties between matrices were primarily attributed to the differences in % retention during drying; the effect of which may have surpassed the effect of flavor solvents or manufacturing formulation/process.
The fate of Salmonella in ready to eat cereals.
(2010-04) Hedstrand, Eric Allan
This study was intended to provide insight into the ability of Salmonella to survive in ready-to-eat (RTE) cereal during storage, contaminated post processing. Sweetened toasted oat cereal (STOC) and toasted oat cereal (TOC) were used to elucidate the ability of Salmonella to remain viable for 3 months and the effect of sucrose on its survival. To date, this is the first study to report survival of Salmonella in ready to eat cereal during storage. Commercial cereal samples were inoculated with approx. 106 CFU/g of five different Salmonella strains belonging to four serovars (Agona, Typhimurium, Tennessee and Senftenberg) and re-dried within 24 h. Inoculated cereal was periodically sampled after drying on 1, 3, 5, 7, 14, 30, 60, and 90 days of storage at room temperature. The viable Salmonella count was determined using complex differential media and standard microbiological techniques. The count of most serovars increased during the cereal re-drying step in TOC, but not in STOC. During storage the Salmonella count remained greater than 107 CFU/g in TOC for the entire experimental period with the exception of serovar Senftenberg. The level of Salmonella in STOC declined during the first week of storage, but their final counts were more than 103 CFU/g. These results indicated that Salmonella was able to survive for at least ninety days in either type of cereal. The relevance of this research to the cereal industry is that it confirms the unique ability of this microorganism to survive conditions of very low water activity and stresses the importance of further processing to minimize the risk of transmission of this pathogen by cereal foods.
Functional Properties of Camelina Protein Concentrate Extracted by Hot Oil-Pressing and Salt Precipitation and the Effect of Hydrolysis on Protein Functionality
(2018) Hansen, Lucy;
There is a continued demand for high protein foods, and plant proteins in particular are trending. Camelina is a sustainable oil seed that is emerging as a new potential protein source, although there is currently not much information available on camelina for food use. The objectives of this study were to characterize select functional properties of camelina seed after hot oil-pressing and extraction by salt precipitation. A portion of the resulting camelina protein concentrate was enzymatically hydrolyzed in attempt to improve solubility and functional properties. Whey protein isolate and soy protein isolate were also tested for comparison. SDS-PAGE was performed to characterize subunits within each protein. Solubility was measured at pH 3.4 and 7.0 under heated and non-heated conditions. The emulsification capacity, emulsion stability, gel strength, and water holding capacity were assessed. The solubility of camelina protein was slightly greater than SPI at pH 3.4 but inferior to WPI. At pH 7.0, the solubility of camelina protein was inferior to both WPI and SPI, which also led to inferior functionality as tests were conducted at pH 7.0. One notable exception was that the water holding capacity of camelina was equivalent to that of SPI with nearly 100% water retention. Hydrolysis at DH 8.6% was found to have a neutral or negative impact on all functional properties of camelina protein. Further research on camelina protein should be performed, particularly at an acidic pH to determine if its functional properties could be superior to SPI under acidic conditions.
Improving the functionality and bioactivity of wheat bran.
(2012-04) Petrofsky, Keith Eric
Wheat bran, including the aleurone layer, contains the vast majority of phenolic antioxidants found in the wheat kernel. Unfortunately, about 80% of phenolic acids in wheat bran are structurally bound and insoluble. These bound phenolics are neither bioactive nor bioavailable during digestion. Additionally, wheat bran contains 43% total dietary fiber, but only 3% soluble dietary fiber. Insoluble fiber is less functional than soluble fiber which has been shown to lower cholesterol and regulate blood sugar. We hypothesized that processing could improve the functionality of wheat bran and bioavailability of phytochemicals in the bran. Specifically, we aimed to maximize the physical properties of viscosity and water hydration capacity in wheat bran, while also maximizing the release of bound phenolic antioxidants from the bran. Wheat bran processing included physical treatments of dry grinding, high shear mixing, high pressure homogenization (HPH), and alkali chemical treatments with different concentration, time, and temperature. Sample analysis included particle size, Wheat bran, including the aleurone layer, contains the vast majority of phenolic antioxidants found in the wheat kernel. Unfortunately, about 80% of phenolic acids in wheat bran are structurally bound and insoluble. These bound phenolics are neither bioactive nor bioavailable during digestion. Additionally, wheat bran contains 43% total dietary fiber, but only 3% soluble dietary fiber. Insoluble fiber is less functional than soluble fiber which has been shown to lower cholesterol and regulate blood sugar. We hypothesized that processing could improve the functionality of wheat bran and bioavailability of phytochemicals in the bran. Specifically, we aimed to maximize the physical properties of viscosity and water hydration capacity in wheat bran, while also maximizing the release of bound phenolic antioxidants from the bran. Wheat bran processing included physical treatments of dry grinding, high shear mixing, high pressure homogenization (HPH), and alkali chemical treatments with different concentration, time, and temperature. Sample analysis included particle size, viscosity, water hydration capacity (WHC), water extractable material (Wa-Ex), free phenolics, and visual imaging by scanning electron microscopy (SEM). Prescreening results showed that while HPH helped reduce particle size of bran regardless of treatment, only alkali chemical treatments released the vast majority of bound phenolics. Alkali treatments also contributed to viscosity increase, with interaction of variables of alkali concentration, treatment time, and temperature. Variables for optimization studies included bran grind, alkali concentration, reaction time, and reaction temperature, while process treatments that remained constant were high shear mixing after chemical pretreatment and HPH conditions. Two factorial designs were conducted to optimize viscosity and WHC of bran while maximizing release of bound phenolics. The second factorial design was an augmentation to the first and data was combined for statistical analysis. Viscosity maximum was reached using 0.5mm screen size in bran dry grinding and chemical treatment conditions of 60°C soak temp, 24 hour soak time, 0.1N NaOH concentration. WHC maximum was reached using 0.5mm screen size in bran dry grinding and chemical treatment conditions of 48°C soak temp, 20 hour soak time, 0.7N NaOH concentration. Overall, process optimization was successful and produced wheat bran with a 500% increase in viscosity, 200% increase in WHC, 500% increase in soluble fiber, and a 300 fold increase in free and soluble bound phenolic antioxidants. Visual confirmation by SEM validated analysis results and showed the optimized bran had a very open and porous structure due to the chemical weakening of the alkali treatment and high shear pulverization of the HPH treatment. The optimized viscosity process was scaled up to produce a large quantity of samples for further research in this collaborative study. Work to separate or concentrate the soluble fraction of processed bran utilized centrifugation to produce additional samples of more soluble and more insoluble processed bran fractions.
Incorporating tasting into an experimental auction.
(2010-06) Zhang, Kathryn Marie
Abstract summary not available
Natural whole grain components effectively control TNF alpha
(2009-05) Pascoe, David Allen
The immune system plays a key role in recognizing self and non-self compounds to keep our bodies healthy. This leads to a balancing act to provide sufficient immunological response to appropriate antigenic (foreign) agents, and not over-responding which creates detrimental effects on the host. Betaglucans from bacteria, fungi, and cereal grains are immune system stimulators that work through specific cell surface receptors to enhance the host response against antigenic organisms and tumors. One of the most significant signals the peripheral immune system utilizes to respond to an antigenic agent is the secretion of TNFα cytokine. This pleiotropic cytokine leads innate immune system defense, plays a key role in appetite, inflammation, and cancer, and regulates communication to other immune cells to respond in an organized configuration. First, this study demonstrated that beta-glucan from barley and oat as well as enzymatic treatment of beta-glucans from oats enhances immune stimulation through increased TNFα. I have shown through a model cell culture system (RAW 264.7 macrophages), a highly pure barley betaglucan (>91%; 10 μg/ml) and oat beta-glucan (>97%; 300 μg/ml) stimulate macrophages to produce 0.57 +/- 0.19 and 0.49 +/- 0.17 fg/cell TNFα, respectively quantified by ELISA). However, treatment of barley (10 μg/ml) and oat (300 μg/ml) beta-glucans with lichenase (10 u/μg; 1 hr, 40 C) significantly (p<0.05) increased TNFα production only in the oat beta-glucan (300 μg/ml) samples (1.48 +/- 0.55 fg/cell). Uncontrolled production of TNFα has been well documented in patients with chronic diseases such as CVD, obesity, and diabetes. Drugs that suppress TNFα production have relieved many deleterious symptoms and disease progression associated with these chronic diseases. Second, this study demonstrated that phenolic acids associated with cereal bran reduce TNFα production. Bran extracts from wheat and barley containing phenolic acids can almost completely diminish (~87%) the TNFα production from macrophages stimulated by cereal and bacterial beta-glucans. Purified commercially available cinnamic and protocatechuic acid significantly (p<0.05) reduce TNFα production from bacterial and cereal beta-glucan stimulated macrophages. The combined effects of caffeic and ferulic acid significantly reduced TNFα (59-88%) from cereal and bacterial beta-glucan stimulated macrophages. Through a model cell culture system, I demonstrated that beta-glucans, cereal bran extracts, and multiple phenolic acids from cereal bran have the potential to regulate an important cytokine of the immune system.
Novel emulsion-based delivery systems.
(2011-09) Zhang, Jian
Novel emulsions with useful attributes such as improved stability, clarity and label friendliness were investigated in this thesis. Overall, this thesis has three parts: the first part systematically studied the formation and optical properties of nanoemulsions; the second part focused on formation and beverage cloud application of multilayer emulsions; and the third part evaluated the formation, stability and beverage cloud application of multiple phase emulsions. In part 1, nanoemulsions were prepared using four different food grade biopolymers (different concentrations) and high pressure homogenization (Microfluidizer®, different pressures, temperature and number of passes). It was found that increasing number of passes through the microfluidizer led to a wider particle size distribution. The effect of oil types on mean droplet diameter (MDD) was complex being dependent on the emulsifier, homogenization pressure, phase viscosity and number of passes. It was also found that interface composition, relative refractive index, volume fraction of dispersed phase and droplet size influenced the turbidity. A polynomial relationship was found between MDD and turbidity within the MDD range of 80 to 400 nm. The effects of lipid phase and interface composition on turbidity were droplet size dependent. A linear relationship between volume fraction of dispersed phase and turbidity was established. Experiment results demonstrated that matching refractive indices between phases led to clear emulsions. Finally the primary destabilization mechanism of MCT nanoemulsions emulsified with modified starch was identified as coalescence from a two-week shelf life study. In part 2 of this thesis, the ability to prepare secondary and tertiary beverage cloud emulsions using a layer-by-layer deposition technique was developed. Proteins, β-lactoglobulin (L) and sodium caseinate (S), were selected to stabilize the primary emulsions. Biopolymers of sodium alginate (S), ι-carrageenan (C), gum Arabic (G), pectin (P), chitosan (Ch) and gelatin (Ge) were evaluated as secondary and tertiary layers. Biopolymer concentration and pH were found critical to the formation of stable multilayer emulsions. Protein and polysaccharide type also impacted droplet size and δ-potential of multilayer emulsions. Interestingly, β-lactoglobulin was found better than sodium caseinate in forming protein-polysaccharide interfacial complexes as demonstrated by smaller MDD of LA, LP and LC than those of SA, SP and SC. It was also found biopolymer concentration has to be above a critical value (0.2 ~ 0.5% w/w) to prevent multilayer emulsions from bridging flocculation. Our data showed that both secondary (LA, LC, LG) and tertiary (LGC) emulsions formed by electrostatic deposition could provide the same performance as traditional emulsifiers of gum Arabic (G) and modified starch (M). After four weeks of storage at room temperature, beverage clouds stabilized with G, M, LA, LC, LG and LGCh showed MDDs of 0.68, 0.67, 0.90, 0.82, 0.65 and 2.2 μm, respectively, and turbidity losses of 18, 28, 22, 19, 25 and 17%, respectively. In part 3 of this thesis, water-in-oil-in-water emulsions (W/O/W, also called double emulsions) were studied using a concentrated sucrose solution as a natural weighing agent to increase the density of the oil phase. The results indicated that MDD of W/O emulsions decreased with increasing emulsifier (polyglycerol polyricinoleate, PGPR) concentration. Homogenization pressure and number of passes through a microfluidizer affected MDD, size distribution and encapsulation efficiency (EE) of yellow #6 (included in the water phase as a marker to measure EE). The hydrophilic emulsifier type and oil phase showed great impacts on EE and stability of the W/O/W emulsions. A high EE (>85%) was achieved in gum acacia (GA) stabilized double emulsions whereas Tween 20 and modified starch (MS) stabilized double emulsions showed low EE (< 50%) demonstrating that the type of hydrophilic emulsifier is a critical factor governing stability of double emulsions. Gelling the inner aqueous phase proved to be ineffective in improving EE and stabilizing double emulsion in this study. Results on beverage cloud applications of W/O/W emulsions indicated that GA stabilized emulsions are more stable to turbidity loss and ring formation than those stabilized by MS. Beverage clouds containing OT-based W/O/W emulsions without gelling the inner phase showed low turbidity loss during shelf-life without ring formation demonstrating potential commercial value of these emulsions.
Prediction of mandarin juice flavor: a flavoromic approach.
(2011-06) Charve, Joséphine Isabelle Marie
This thesis introduces an alternative approach to predict flavor and is referred to as flavoromics; this research adapts concepts and tools from metabolomics investigations. It is a non-targeted strategy combined with chemometrics which considers for study all (ideally) low molecular weight compounds in foods as candidate chemical stimuli in human flavor perception. The feasibility of flavoromics to predict the intensities of various flavor attributes was tested on mandarin juice. Forty-six juices were characterized by both instrumental and descriptive sensory analyses. Volatiles and non-volatiles were analyzed by headspace solid-phase micro extraction gas chromatography and solid-phase extraction ultra high performance liquid chromatography- time of flight mass spectrometry, respectively. The developed methods were a compromise between the number of compounds extracted and detected, throughput, and repeatability. The capability of distinguishing samples based on mass spectral information collected from the different instruments using chemometrics was confirmed. The descriptive sensory analysis of the mandarin juice samples revealed very different flavor profiles between and within hybrids and cultivars, and juices made from fruits with common genetic background tended to share some sensory characteristics. Compositional variations across mandarin juice samples and their sensory profile were correlated using partial least squares regression, from which different predictive models of sensory quality were developed. The explanatory and predictive performances of the models were improved when combining all instrumental data into one single data set as opposed to individual ones, indicating that each individual subset conveyed complementary information and that merging them improved the overall description of the sensory profile. The best PLS model was obtained with mid-level data fusion, for which a preliminary variable selection was done. The predictive power of the selected model was tested using a calibration and prediction sample sets. A fairly robust model was obtained and a strong relationship between instrumental and sensory measurements was observed. The resulting model showed that prediction of sensory scores was possible to a certain extent for a majority of the sensory descriptors, demonstrating the applicability of using a data-driven approach to predict flavor irrespective of whether the chemical identity of the instrumental signals was known or not.
Rapid Detection and Discrimination of Bacillus Species Using IMS-SERS
(2012-04-18) Deen, Bronwyn
Bacillus species are gram positive, spore-forming bacteria which include B. anthracis, a class A bioterrorism agent according to the Centers for Disease Control and Prevention. Because of anthrax’s high toxicity, it is important to be able to quickly and accurately detect B. anthracis spores. Immunomagnetic separation (IMS) has previously been shown to capture toxins from complex media, such as food. Subsequent detection with Surface-Enhanced Raman Spectroscopy (SERS) has been shown to be highly sensitive for detection and discrimination of other toxins. This research aimed to discriminate three different Bacillus species and establish a procedure based on IMS-SERS that can detect B. anthracis in under 20 minutes. We found that the Bacillus species could be differentiated when SERS spectra were analyzed using principal component analysis; discrimination between cell states could be achieved with SERS when using hierarchical cluster analysis. The limit of detection was 2*104 spores/mL due to inconsistency of the raman signal as a result of incomplete coverage of the silver dendrites. In order to achieve a lower limit of detection, the spores were treated with dodecylamine, which rapidly digests the sporal coat, following IMS and adds little time to sample preparation. Upon digestion, the spore biomarker dipicolinic acid (DPA) is released. DPA is a highly raman-active compound, which allows for use as a raman marker and due to its high abundance in the spores, allowed for a lower limit of detection at 1* 104 spores/mL. Based on published toxicological data, detection at these limits is sufficient for protecting the public in case contamination of food.
Real-time release of volatile and non-volatile components from chewing gum using a mechanical chewing device.
(2010-11) Krause, Andrea Jean
To date, the majority of research on chewing gum has been conducted using human subjects in conjunction with time-intensity sensory analysis and/or real-time mass spectrometry techniques (proton transfer reaction mass spectrometry [PTR-MS] or atmospheric pressure ionization [API-MS]). The disadvantages of human subjects include their tremendous variability (salivary flow rate, masticatory force, mouth volume, mastication rate, respiration rate, and others), low throughput of samples, and necessary training and compensation. For these reasons, it is desirable to fabricate a chewing device to simulate human mastication. Using this device, formulation and ingredient effects could be elucidated without convolution by inter-individual differences. The trade-off, however, is a lack of end-user perception, a potentially large capital investment, and difficulty replicating the conditions associated with human mastication. In the work presented herein, we have developed such a chewing device to be used as a screening tool for ingredients and formulation effects in chewing gum. The device simplifies the chewing process so a more basic understanding of the release of volatile and non-volatile components from chewing gum can be achieved.
Sensory aspects of astringency and changes of the oral environment in the mechanism of astringency.
(2010-08) Lee, Catherine A.
Astringency, a tactile sensation felt in the mouth after exposure to various foods, is not well understood. The underlying mechanism is not fully known, and it remains a challenging attribute to assess in sensory tests. Additionally, while most food astringency is caused by polyphenolic compounds, the cause of astringency in some other foods is not known. For the first part of my research, my objective was to improve the understanding of the mechanism of astringency by determining if it was related to a loss of saliva's ability to lubricate, the precipitation of specific classes of salivary proteins, or to the removal of oral lubricating films that coat the inside of the mouth. My results show that while astringency may be related to the latter, astringency is not related to a loss of salivary lubricity or the precipitation of any one class of salivary proteins. The second part of my research aimed to improve palate cleansing strategies for astringent foods. Palate cleansers are often used in an attempt to reduce build-up of astringency intensity that occurs over repeated exposures to astringent foods, but it is unknown how, or if, commonly used palate cleansers affect a person's sensitivity to astringency. Although I did not find that any of the cleansers were superior in their ability to limit the build-up of astringency intensity, it was clear that panelists were better able to discriminate among the astringency of various strength solutions when they used nothing or water to cleanse their palates. The aim of part III of my research was to determine the cause of astringency in acidic whey protein beverages. Although some believe that the whey proteins directly cause the astringency, there was reason to suspect that their high acid concentration was instead responsible. The results of my study found this to be true.
Stability and release of model aroma compounds.
(2008-08) Leclercq, Ségolène
Overall, this thesis has two parts: The first evaluated the use of complex coacervation for aroma encapsulation to control aroma release. The second part focused on improving the storage stability of encapsulated aroma compounds by different techniques. In part 1 coacervate capsules were formed using gelatin and gum acacia as wall materials and either a liquid or solid core (aroma compounds). A brief storage study compared the oxidation barrier properties of coacervate capsules and spray dried powder. No significant oxidation of limonene was detected in coacervate capsules after 25 days, whereas significant oxidation was found in spray dried powder. Then the effect of coacervate capsule properties on volatile release (measured using proton transfer reaction MS) was studied. No significant effect of glutaraldehyde cross-linking or wall:core ratio on aroma release was found. Comparing aroma release data from coacervates to their release from a spray dried material, no significant difference in release pattern could be found. However, testing temperature, aroma volatility and hydrophobicity were found to be significant but not predictive factors. In the second part of this thesis, the storage stability (12 weeks at 30 °C) of volatiles was found to be significantly decreased by the presence of oxygen and the type of matrix in which compounds are diluted (water or various edible oils). Medium chain triglycerides, sunflower oil and soy bean oil were evaluated as the edible oils. Water was found to have a highly significant detrimental effect on volatile stability compared to the oils. The type of oil matrix was also found to significantly affect storage stability. No correlation could be detected between the oxidation level of the oil and the oxidation pattern of the volatiles.
Thermal and chemical inactivation of ricin and Shiga toxins in orange juice.
(2010-01) Wang, Na
The potential use of ricin and Shiga toxins (Stxs) as bioterror weapons in the food supply is a major concern for homeland security. Denaturation effects of thermal and chemical treatments are expected to reduce the toxicity of ricin and Shiga toxins in water solutions, but their effectiveness and stabilities in food matrices are largely unknown. The objective of this project was the identification of heat and chemical treatments capable of inactivating ricin and Shiga toxins in orange juice so that large quantities can be safely disposed in the event of an intentional attack. Diluted ricin was mixed with orange juice for inactivation studies. Thermal stability was determined in capillary tubes using a water bath at high temperatures typical of pasteurization. For chemical inactivation, sodium hypochlorite (NaOCl), sodium hydroxide (NaOH) and peracetic acid (PA) were added alone or in combination to samples with or without thermal treatment. The ricin concentration in samples was determined using an ELISA. The Arrhenius model was used to evaluate temperature dependence. Enterohemorrhagic Escherichia coli strains were used to produce Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). Shiga toxins were added into phosphate buffered saline (PBS) or orange juice to study the inactivation effects. The same inactivation method was also used for heat treatment of Stxs. The concentration of Stxs was determined by an ELISA and a cytotoxicity assay was conducted to confirm the inactivation. Kinetics studies were done to evaluate inactivation parameters. Heat inactivation of ricin followed first-order kinetics. The half-life (t1/2) of ricin at 72, 80, 85 and 90°C were 72.6, 9.0, 2.0 and 0.5 min, respectively. The Z value was 8.8°C indicating high temperature sensitivity. When the concentration of each chemical was increased to a sufficient amount, the detection limit of the ELISA kit was reached when measuring ricin inactivated within 5 s at room temperature. A significant synergism between NaOCl and NaOH and considerable efficacy with treatment with PA alone were observed. The heat inactivation of Stxs in PBS and orange juice also followed first-order reaction kinetics. Both Shiga toxins in PBS and orange juice would reach the concentration that was not detectable with ELISA within 30 s at 90°C and 120 s at 85°C. The Z values for Stx1 and Stx2 were 6.7 and 7.2°C in PBS as well as 8.7 and 6.9°C in orange juice, respectively. This study delivered the first series of time/temperature/concentration conditions that would serve as the basis for recommendations for treating orange juice subjected to intentional adulteration with ricin or Shiga toxins in an orange juice plant with typical pasteurization equipment so it can be safely disposed into the environment.

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