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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Sustainable Agri-food Production and Consumption

James D. Chapa (5930576) 11 June 2019 (has links)
Agri-food production is necessary to sustain the growing global population, but it adversely impacts the environment in various ways, including climate change, eutrophication, acidification, land and water uses, and loss of biodiversity, etc. These environmental impacts can also negatively affect human health, which could in theory outweigh the health benefits of nutritious food. While better agricultural practices need to be developed and applied to minimize the environmental burdens associated with the production chains, consumers are expected to implement more sustainable lifestyles and eat more environment-friendly foods. Life Cycle Assessment (LCA) is an analytical tool to evaluate the sustainability of a product by examining all the resources used and emissions generated during its life cycle. The first part of this work focused on the upstream production. An LCA of organic blueberry production was conducted to evaluate the trade-off between seasonal and local options and answer the question of whether imported fresh or domestic frozen blueberries are more sustainable. Fresh blueberries from Chile showed superior environmental performance within 2-week storage, due to lower electricity use associated with refrigeration and higher farming yield. Furthermore, length of storage and transportation distance were also found important; if farming yields are comparable, consumption of locally produced, fresh blueberries will be a better choice because of less energy use and shorter transportation distance. The second part of this work targeted at the downstream consumption and aimed to reduce the U.S. environmental footprint through changing adult eating habits. Supplemental functional units were applied in the LCA to incorporate the functions of food to provide nutrition and satiety. With controlled caloric intake, vegetarian diets were found overall more sustainable. However, large possible variations in the environmental impacts of the compared diets were observed due to wide range of nutritional quality of selected foods. Animal products, including meat and dairy especially, and discretionary foods were identified as hotspots in the American diet, that is, reducing the consumption of these foods or deliberately choosing more sustainable alternatives within the same food categories, like chicken and low-fat milk, can significantly improve the sustainability of current American dietary patterns. <br>
42

Differential Effects of Chronic Low Calorie Sweetener Consumption on Body Weight, Glycemia, and Ingestive Behavior

Kelly A. Higgins (5929742) 17 January 2019 (has links)
<p>Low calorie sweeteners (LCS) provide sweetness with little to no energy. Each sweetener has a unique chemical structure that possesses unique sensory and functional characteristics. While LCS are generally considered in aggregate, these unique chemical structures have potential implications for sensory, metabolic, and behavioral differences that may impact body weight and glycemia. Therefore, two, twelve-week experiments were conducted to determine the effect of chronic LCS consumption on body weight, glycemia, and ingestive behaviors. </p> <p>The first experiment investigated the differential effects of four LCS (saccharin, aspartame, rebaudioside A, and sucralose) and sucrose consumed for twelve weeks on body weight, glycemia, and ingestive behaviors among healthy adults with overweight or obesity (body mass index (BMI) between 25 and 40 kg/m<sup>2</sup>). In a parallel-arm design, 154 participants were randomly assigned to consume 1.25 to 1.75L of beverage sweetened with 1 of the 5 sweeteners daily for 12 weeks. Body weight was measured every two weeks; energy intake, energy expenditure, and appetite were assessed every 4 weeks; and glucose tolerance was measured at baseline and week 12. Every four weeks, participants completed 24-hour urine collections to determine study compliance via PABA excretion. Sucrose and saccharin consumption led to increased body weight across the 12-week intervention (Δ weight = +1.85 and +1.18kg, p ≤ 0.02) and did not differ from each other. While there was no significant change in body weight with consumption of the other LCS treatments compared to baseline, changes in weight in comparison to the sucrose treatment (sucrose – LCS) were significantly different for aspartame, rebA, and sucralose after 12 weeks (weight difference = 1.13, 1.25, 2.63kg, respectively; p ≤ 0.03). In addition, change in body weight at week 12 was significantly lower between sucralose and all other LCS (weight difference ≥ - 1.37 kg, p=0.008).</p> <p>The second experiment investigated the effect of daily aspartame ingestion on glycemia, body weight, and appetite. One hundred lean (BMI between 18 and 25 kg/m<sup>2</sup>) adults were randomly assigned to consume 0, 350, or 1050 mg aspartame/day for twelve weeks in a parallel-arm design. This experiment followed a similar protocol but measured body weight and blood pressure weekly and contained a 240-min glucose-tolerance test (OGTT) with measurements of selected hormones at baseline and week 12. Participants also collected 24-h urine samples every four weeks. There were no group differences for glucose, insulin, resting leptin, glucagon-like peptide 1, or gastric inhibitory peptide at baseline or week 12. There also were no effects of aspartame ingestion on appetite, body weight, or body composition. </p> <p>These trials demonstrate that all LCS contribute negligible energy but should not be aggregated because of their differing effects on body weight. Sucrose and saccharin consumption significantly increased body weight compared to aspartame, rebA, and sucralose. This differential change in body weight among LCS indicates individual LCS likely exert different physiological responses beyond the contribution of sweetness with negligible energy. Saccharin, rebA, sucralose, and aspartame (ingested at three doses) for twelve weeks had no effect on glycemia. These data do not support the view that LCS are problematic for the management of glycemia. If substantiated through additional testing, findings from this trial have implications for consumers, food industry, clinicians, and policy makers. Some LCS may not hold the anticipated beneficial effects on body weight (e.g., saccharin) and positive effects of one LCS (sucralose) may be attenuated if combined with select other LCS. Going forward it will be important to consider each LCS as a distinct entity with respect to its potential health effects.</p>
43

FOOD MATERIALS SCIENCE: EFFECTS OF POLYPHENOLS ON SUCROSE CRYSTALLIZATION AND CHARACTERIZATION AND CREATION OF ALTERNATIVE SALTS OF THIAMINE

Collin J. Felten (5930618) 17 January 2019 (has links)
<div> <p>Proper understanding of materials science is critical in understanding the functionality of ingredients in food products, as well as their behavior in these products over time. Amorphous materials are metastable, eventually rearranging to the thermodynamically stable crystalline state. Amorphous materials have properties which are beneficial in some food products: they are softer in texture and dissolve more rapidly. The amorphous state of sucrose might provide an increase in quality in applications like powdered beverages where rapid dissolution is preferred. A number of classes of compounds have been shown to delay the crystallization of amorphous sucrose; however, polyphenols, particularly their glycosylated forms, have been little explored. Glycosylated polyphenols contain two distinct structural regions: a more hydrophilic sugar unit(s) and a more hydrophobic polyphenol backbone. While the sugar unit should be able to easily associate with sucrose molecules, the polyphenolic backbone may not and might provide hindrance to crystal nucleation and growth.</p> <p> </p> <p> Thiamine is an essential nutrient that is found naturally in foods such as whole grains and pork. The processing of grains removes nearly the entirety of the natural thiamine content; thus, foods are often enriched with synthetic thiamine. Two salts of thiamine are used commercially: thiamine mononitrate and thiamine chloride hydrochloride. The two forms have specific applications driven by their specific properties, specifically their aqueous solubility and hygroscopicity. While these two salts provide adequate functionality, it is possible new salts may have properties beneficial in certain food applications. A method making use of silver nitrate was developed to produce new salt forms. An intermediate in this reaction, TCl·H<sub>2</sub>O, was characterized including measurements of stability in aqueous solutions and solid state properties.</p> </div> <br>
44

Advanced Characterization of Glucan Particulates: Small-granule Starch, Retention of Small Molecules, and Local Architecture Defined by Molecular Rotor

Xingyun Peng (5930138) 04 January 2019 (has links)
<p>The discovery and utilization of novel starches with unique superb properties are highly demanded for modern industrial uses. Small-granule starch (SGS) is a category of unconventional starches with the granular size smaller than 10 μm. The potential use of SGS includes many conventional and novel high-value applications, such as texturizing, fat replacement, encapsulation, controlled delivery and nano-engineering. In the present work, we focused on three SGS isolated from amaranth (<i>Amaranth cruentus</i>), cow cockle (<i>Saponaria vaccaria</i>) and sweet corn (<i>sugary-1</i> maize mutant). The basic structural and unique physical properties of SGS were characterized and compared to common large-granule food starches. It was found that (1) the highly branched amylopectin contributed to low crystallinity and pasting viscosities of sweet corn starch, (2) cow cockle starch exhibited high shear-resistance and low retrogradation in prolonged storage, and (3) the amylopectin for amaranth starch was less branched with small clusters, which was associated with the high crystallinity, medium shear-resistance and low pasting viscosity of amaranth starch. Despite the small size of starch granules, SGS in both native and swelling states showed the capacity of retaining small molecules. Compared to large-granule starch, native SGS are more difficult for small molecules to reach an equilibrium permeation. This work provides insights to the fine structure and physicochemical behaviors of selected high-potent SGS, which is believed to support the industrial production and application of SGS in the future.</p> <p>The characteristics of local polymeric structure dominate many critical properties of glucan particles, such as starch retrogradation and the loading and stabilizing of active substance. Molecular rotor (MR), a fluorescent probe, was proposed to fulfill the simple, high-sensitive, and quantitative-based characterization of local glucan architecture (LGA). In the present work, two innovative studies relevant to this novel method were conducted: (1) MR was able to characterize glucans based on its unique fluorescent response to characteristic LGA, (2) MR was able to sensitively probe and visually demonstrate the transition of LGA induced by starch retrogradation. This novel MR-based approach is expected to advance carbohydrate-related researches in the future.</p>
45

Investigating Stability in Amorphous Solid Dispersions: A Study of the Physical and Chemical Stability of Two Salt Forms of Thiamine and the Physical Stability of Citric Acid

Seda Tuncil (5930339) 03 January 2019 (has links)
The majority of water soluble vitamin and organic acid food additives are distributed in their crystalline forms. However, when they are combined with water and other food ingredients and then exposed to a variety of unit operations, there is potential to solidify these initially crystalline ingredients in the amorphous state. Amorphous solids are generally less chemically and physically stable than their crystalline counterparts. To ensure nutrient delivery to the consumer and fulfill labeling laws, deterioration of nutrients due to unintentional amorphization is undesirable. Additionally, the potential for recrystallization of an amorphous ingredient may alter texture and redistribute water. Hence, solid state form is a critical factor dictating the stability of food formulations. Building on earlier work from my M.S. degree that demonstrated thiamine chloride hydrochloride could solidify in the amorphous state in the presence of a variety of polymers (Arioglu-Tuncil et al., 2017), a major goal of this study was to develop a comprehensive understanding of the physical and chemical stability of amorphous forms of two thiamine salts, thiamine chloride hydrochloride (TClHCl) and thiamine mononitrate (TMN), in comparison to their crystalline counterparts and each other. The objectives for this part of the work were to investigate amorphization/recrystallization tendencies of TMN and TClHCl in solid dispersions, as well as chemical stability of thiamine in the solid dispersions to understand the impact of vitamin form, physical state (amorphous vs. crystalline), polymer type and features (Tg, hygroscopicity, and ability for intermolecular interactions), storage conditions, proportion of vitamin to polymer,and pre-lyophilized solution pHs on thiamine degradation and the physical stability of dispersions. Thiamine degraded more when in the amorphous form compared to in the crystalline state. Additionally, polymer type and vitamin proportion influenced thiamine degradation, where thiamine degraded more when it was present in lower concentrations (in dispersions that had higher Tgs), and it was chemically more stable when a polymer with greater intermolecular interactions with the vitamin was used. As storage RH increased, variably hygroscopicities of the polymers resulted in different thiamine degradation rates. The pre-lyophilization pHs of the solutions had a significant impact on thiamine stability in the solid dispersions. Similar to thiamine salts, citric acid is a commonly used food ingredient with a high crystallization tendency. Following similar experimental designs for documenting the recrystallization tendencies of citric acid in amorphous solid dispersions to those used in the thiamine studies, hydrogen bonding and/or ionic interactions between polymer and citric acid were found to be the main stabilizing factor for delaying recrystallization, more than polymer Tg and hygroscopicity. The findings of this dissertation provide a powerful prediction approach to physically and chemically stabilize the small compounds in the complex food matrices for the production of high quality food products and ensuring nutrient delivery to target populations.<br>
46

PERFORMANCE OF NOVEL PORTABLE SOLAR DRYING TECHNOLOGIES FOR SMALL AND MID-SIZE GROWERS OF SPECIALTY CROPS UNDER INDIANA WEATHER CONDITIONS

Diana M Ramirez Gutierrez (8158146) 20 December 2019 (has links)
<div>The overall goal of this thesis was to study the performance of two related portable multipurpose solar dryers, DehytrayTM and DehymeleonTM, in comparison to open-air sun drying by drying tomatoes, apples and mint under West Lafayette, Indiana weather conditions. Thin layer drying tests were conducted on tomato slices, apples slices and mint leaves, with three temperatures [24°C (75°F), 35°C (95°F) and 54 °C (130°F)], and an airflow velocity of 1 m/s to determine the drying kinetics of these products during diurnal drying cycles typical for solar and/or open-air sun drying. Subsequently, field drying tests were conducted for tomatoes slices, apples slices and mint leaves with the two solar drying technologies (DehymeleonTM and DehytrayTM) and open-air sun drying using uncovered Dehytrays as the control. The average temperatures achieved for these technologies were 45°C (113°F), 60°C (140 °F) and 27°C (80.6 °F) for the DehymeleonTM, DehytrayTM and open-air sun drying, respectively. Moisture diffusivity were in the order of 10-4 to 10-9 (m2/s) for the different methods, depending directly on the product, temperatures and air flow inside the drying chamber.</div><div><br></div><div>Quality attributes (color, vitamin C and microbial growth) were measured before and after the field drying tests. Color difference (ΔE) for DehymeleonTM solar dryer showed the least variation compared with the fresh products. However, for the DehytrayTM ΔE increased due to the impact of its higher temperature and direct sunlight exposure that led to Maillard reactions and caramelization in the case of tomatoes and apples slices. Additionally, vitamin C (Ascorbic acid) content for tomatoes and apples slices was affected for the high ranges of temperatures reached inside the Dehytray™. Denaturing of vitamin C was less observed for DehymeleonTM, maintaining values of 166 mg/100 g dm for tomatoes, and 104.2mg/100g for apples slices. There was no significant difference (α = 0.05) in the microbial growth for the DehytrayTM and open-air drying compared to the fresh product, however, there was significant difference for the DehymeleonTM when drying tomatoes and apples slices, without up one log reduction on the original microbial population. In the case of mint, DehymeleonTM had a 2.3 log reduction, which is similar to L-lactic acid sanitizer achieved by another study in the literature, compared with 0.4 log obtained by the DehytrayTM and 0.47 log obtained by open-air sun drying. The differences in microbial growth were observed because the temperatures inside the drying chamber of the DehymeleonTM was low and product moisture content was above the safe equilibrium moisture content (EMC) for both tomatoes and apples during the early critical hours at the onset of the drying process, which was favorable to mold growth. The lack of a fan to intermittently or constantly flush out humid air released from the crop dried in the DehytrayTM negatively affected its performance. The insufficient airflow in the drying chamber of the DehymeleonTM and its inability to achieve the high temperatures observed in the DehytrayTM negatively affected its performance. Both solar dryers, DehymeleonTM and DehytrayTM achieved high hygienic condition during drying due to their enclosed chambers than protected the crop from contaminant in the environments. Their portability and design for large-scale manufacturing and deployment are a positive development that would be helpful to small and mid-size growers, as well as households (home gardens). Areas for further research were highlighted.</div><div><br></div><div><br></div>
47

IMPROVEMENT OF FUNCTIONAL AND BIOACTIVE PROPERTIES OF CHIA SEED (SALVIA HISPANICA) PROTEIN HYDROLYSATES AND DEVELOPMENT OF BIODEGRADABLE FILMS USING CHIA SEED MUCILAGE

Uriel C Urbizo Reyes (7909295) 14 January 2021 (has links)
<div> <p>Chia seed (<i>Salvia hispanica</i>) has shown potential as an alternative source of nutrients with a high content of fiber (36 %), protein (25%), and fat (25%). Unfortunately, the presence of a viscous biopolymer (mucilage), surrounding the chia seed (CS), limits the accessibility of the protein and other nutrients. Nevertheless, this biopolymer’s chemical composition makes it suitable for the development of biodegradable films. Regarding CS protein, disulfide bonding, and nonprotein-protein interactions often frequent in plant protein, have limited its technological application in food matrices. Therefore, scientists have pointed at processing methods involving enzymatic proteolysis to improve the functionality of plant protein ingredients. The objective of this study was to establish processing techniques to exploit the functionality, extraction, and health benefits of chia seed components. First, ultrasonication followed by vacuum-filtration was used to separate mucilage from CS prior to fat extraction by oil press. Mucilage-free and defatted CS were treated using conventional (enzymatic hydrolysis with alcalase) or sequential (enzymatic hydrolysis with alcalase+flavourzyme), and under water bath or microwave-assisted hydrolysis. Chia seed protein hydrolysates (CSPH) derived from the sequential hydrolysis with microwave treatment showed superior (p<0.05) in vitro antioxidant activity. The highest (p<0.05) cellular antioxidant activity was achieved by the sequential (94.76%) and conventional (93.13%) hydrolysis with microwave. Dipeptidyl peptidase-V inhibition was higher (p<0.05) for sequential hydrolysis with water bath, while Angiotensin-Converting Enzyme (ACE) inhibition activity increased (p<0.05) with hydrolysis for all treatments compared to the control. Regarding functionality, sequential hydrolysis with microwave showed higher (p<0.05) solubility at lower pH (3 and 5), while conventional hydrolysis with microwave was better at pH 7 and 9. Emulsification properties and foaming capacity were also higher in conventional hydrolysis with microwave, but conventional hydrolysis with water bath was more stable for foaming properties only. In terms of mucilage applicability, biodegradable films were developed by casting technique where CS mucilage was plasticized with different polyol mixtures (sorbitol and glycerol). CS mucilage films with higher sorbitol content showed superior tensile strength (3.23 N/mm<sup>2</sup>), and lower water vapor permeability (1.3*109 g/ m*s*Pa) but had poor flexibility compared to other treatments. Conversely, films with high glycerol content showed high elongation at break (67.55%) and solubility (22.75%), but reduced water vapor permeability and tensile strength. The hydrophobicity, measured as water contact angle, was higher (p<0.05) for mixtures containing equal amounts of polyols. Lastly, Raman Spectroscopy analysis showed shifts from 854 to 872 cm<sup>-1</sup> and 1061 to 1076 cm<sup>-1</sup>, which corresponded to β(CCO) modes. These shifts represent an increase in hydrogen bonding, responsible for the high tensile strength and decreased water vapor permeability. This study demonstrated that ultrasonication followed by vacuum filtration can successfully separate mucilage from chia seeds; microwave-assisted and enzymatic hydrolysis generated protein hydrolysates with improved bioactivity and functionality. Finally, chia seed mucilage was able to form films with potential to be used in drug delivery and edible food coating applications.</p> </div> <br>
48

DEVELOPMENT OF EARLY POSTMORTEM TUMBLING METHODS TO IMPROVE TENDERNESS AND PROTEOLYSIS OF FRESH BEEF LOINS

Mariah Jean Nondorf (11798321) 20 December 2021 (has links)
<p>Historically, the meat industry has struggled to provide consumers with consistent beef tenderness. Various post-harvest technologies have been used in industry; however, there is still a need to develop a natural and safe post-harvest processing system that can be used to create consistently tender products for consumers. In addition to postmortem aging being a time-consuming process, literature has suggested that it is not a sufficient method to achieve tenderization in certain cull cow muscles. This has resulted in the large supply of cull cow beef to be underutilized due to its inferior quality, specifically tenderness. Applying a combination of mechanical tenderization with additional postmortem aging may be an effective strategy to overcome deficiencies in beef tenderness. Recent studies have found that tumbling without brine addition can be successful at improving instrumental tenderness and consumer liking of tenderness of fresh beef loin. The physical disruptions of muscles, which likely occur during tumbling, may enhance activity of proteolytic enzymes and thus induce more tenderization. The overall objective of this thesis was to investigate the effects of fresh beef tumbling methods and postmortem aging times on the tenderness and proteolysis of loin muscles from both A maturity cattle and cull cows.</p> <p>The first chapter of this thesis is a literature review that will address the factors affecting tenderness and the methods used by the industry to improve tenderness, specifically focusing on meat tumbling and cull cow beef. The second chapter is a study that investigated the effects of fresh beef tumbling at different postmortem times on meat quality attributes and proteolytic features of loins. The results from this study suggest that early postmortem tumbling coupled with aging can synergistically impact the improvements of beef loin tenderness and proteolysis, shortening the necessary aging period. The third and final chapter of this thesis is a study that aimed to determine the effect of fresh beef tumbling and postmortem aging on the quality and proteolysis of loins from cull cows. The results from this study indicate that aging would be effective at improving the quality and palatability of cull cow beef loins, although tumbling could improve consumer liking of tenderness at earlier postmortem times.</p>
49

In vitro and in vivo investigations of carbohydrates with different digestibilities for improved satiety and metabolic health

Anna MR Hayes (8477520) 01 March 2021 (has links)
<p>Obesity and nutrition-related non-communicable diseases continue to be major challenges that are increasing in severity worldwide. Science-centered carbohydrate dietary strategies may be a viable approach to help address such challenges. Recent reports from our laboratory indicate that certain carbohydrates with slow digestion profiles have the ability to trigger the gut-brain axis and reduce food intake and to slow gastric emptying and potentially affect appetite. Slow carbohydrate digestion may have other impacts on energy metabolism that have not been explored. In the current investigations, we sought to better understand the delayed gastric emptying profile of pearl millet-based foods as well as to understand how altering carbohydrate digestion rate impacts substrate utilization for energy.</p> <p>In the first study, the physical breakdown of pearl millet couscous particles in a simulated gastric environment (Human Gastric Simulator) was studied compared to wheat couscous matched in particle size, and select physicochemical properties of each type of couscous were characterized. Because we previously showed that pearl millet couscous had a marked delay in gastric emptying compared to white rice, boiled potatoes, and pasta in a human study in Mali, the objective of the first investigation was to test the hypothesis that pearl millet couscous was more resistant to breakdown in the stomach than wheat couscous and would take longer to empty. Our findings indicated that pearl millet couscous instead broke down into smaller, more numerous particles than wheat couscous. However, pearl millet had a slower starch hydrolysis property compared to wheat couscous per unit surface area. Pearl millet also had a smaller amylose chain length (839-963 DP) compared to wheat (1225-1563 DP), which may enable a denser packing of millet starch molecules that hinders hydrolysis. We also visually observed that the pearl millet particles formed a paste while breaking down that could reasonably generate viscosity in the stomach to potentially delay gastric emptying. </p> <p>Based off the findings from simulated gastric digestion, we next conducted a human study (<i>n</i>=14) in the U.S. to test the hypothesis that pearl millet-based foods (couscous – commercial and self-made, thick porridge) would reduce glycemic response, increase satiety, and delay gastric emptying compared to wheat couscous and white rice. We complemented this human study with additional <i>in vitro </i>work using an advanced gastrointestinal digestion system (TIMagc) to determine if the viscosity of pearl millet couscous particles as they were breaking down in the stomach was contributing to a decrease in gastric emptying. Our findings indicated that all the pearl millet-based foods and wheat couscous had lower overall glycemic response than white rice, but only the self-made millet couscous showed higher satiety through subjective appetitive response ratings. Surprisingly, there were no differences in gastric emptying among the foods. Additionally, the half-emptying times for these foods were all ~3 h, which is similar to the comparably low half-emptying times observed for white rice, boiled potatoes, and pasta in the previous Mali study. We now hypothesize that there may be diet-induced changes in gut-brain axis signaling when slowly digestible carbohydrates are consumed repeatedly over time, perhaps through modulating the number or sensitivity of small intestinal L-cells. We also found that millet couscous did not exhibit high viscosity in the TIMagc, suggesting that viscosity was not impacting its rate of gastric emptying. We conclude that at least some pearl millet-based foods possess a slow digestion property that may act to trigger the gut-brain axis or ileal brake to increase feelings of satiety or slow gastric emptying, but the discrepancy between U.S. and Malian populations requires further study. </p> <p>In the final investigation, we examined how altering carbohydrate digestion affected partitioning of carbohydrate versus fat for oxidation as well as the efficiency of switching oxidation between these two substrates (termed “metabolic flexibility”) in mice. Metabolic flexibility has been associated with good health related to decreased adipose tissue in the body and improved insulin sensitivity and may have implications on weight management. Carbohydrate digestion was adjusted by: (1) testing mice that lacked a complete set of enzymes by knocking out maltase-glucoamylase (Mgam; null) for moderating starch digestion versus testing wild-type mice; (2) using diets in these two groups of mice to moderate starch digestion that had different levels of resistant starch (53%, 35%, and 18%), had only raw corn starch or sucrose, or were high in fat; and (3) providing a supplement of fungal amyloglucosidase (AMG) to the mice treatment groups to increase starch digestion. Respiratory exchange ratio (RER) was measured through indirect calorimetry and mathematical modeling was used to characterize the diurnal shifts in RER (sine equation) as well as carbohydrate versus fat oxidation and metabolic flexibility (percent relative cumulative frequency [PRCF] with Weibull and Mixed Weibull Cumulative Distribution functions). Our results suggest that null mice lacking Mgam had somewhat increased metabolic flexibility than wild-type mice despite exhibiting minimal to no effects on carbohydrate oxidation. Intriguingly, the raw corn starch diet increased fat oxidation and generally promoted metabolic flexibility, although it did not increase carbohydrate oxidation relative to the other carbohydrate-predominant diets. Increasing carbohydrate digestion through AMG supplementation increased carbohydrate oxidation, and generally prompted earlier shifts to carbohydrate oxidation than without AMG supplementation. These findings provide a basis for better understanding the metabolic consequences of altering carbohydrate digestion and establish novel tools that can be utilized in future investigations. Overall, we propose that moderating carbohydrate digestion provides the ideal combination of balancing carbohydrate and fat oxidation while promoting metabolic flexibility. </p> <p>In conclusion, a slow digestion property may enable some types of pearl millet to trigger the ileal brake and gut-brain axis feedback systems to decrease glycemic response and increase satiety. Moreover, consuming carbohydrates with slow digestion may optimize substrate utilization for energy by the body. In addition to triggering the ileal brake and gut-brain axis, modulating carbohydrate digestion to more effectively switch between carbohydrate and fat for oxidation may be beneficial for weight management and metabolic disease prevention.</p>
50

BIOACTIVE AND ALLERGENIC PROPERTIES OF EDIBLE CRICKET (GRYLLODES SIGILLATUS) PEPTIDES

Felicia G Hall (9739430) 10 December 2020 (has links)
<p>Cardiovascular diseases (CVD) and their risk factors remain the leading cause of morbidity and mortality in North America. Food-derived bioactive peptides (BAP) have been shown to play a role in regulating physiological pathways of CVD risk factors including hypertension, diabetes, and chronic inflammation. Common sources of BAP include dairy and plant proteins. In addition to being an alternative protein source, it is now accepted that edible insect proteins can also confer health benefits beyond nutrition. However, as with any novel protein source, allergenicity remains a major concern surrounding edible insect consumption. </p> <p>This dissertation aimed to: 1) Evaluate the bioactive potential of peptides from an edible cricket species and; 2) determine the effects of BAP production methods on immunoreactivity. First, peptide-rich extracts were generated from farmed food-grade crickets via enzymatic hydrolysis techniques with the commercial protease Alcalase™. To measure the <i>in vitro</i> bioavailability, cricket peptides were also subject to simulated gastrointestinal digestion (SGD). Peptides and their digests were tested for relevant bioactivities and active groups were further fractionated by chromatographic methods to identify the major peptides responsible for the bioactivity. When tested for <i>in vitro</i> antihypertensive and anti-glycemic properties, cricket peptides were found to inhibit the activities of angiotensin converting enzyme, dipeptidyl peptidase-4, α-amylase, and α-glucosidase. The anti-inflammatory potential was expounded using RAW-264.7 macrophages and human umbilical vein endothelial cells (HUVEC). Cricket peptides (after SGD) effectively lowered NF-κB, MCP-1, and IL-6 production in cells without affecting their viability. Proteomic analyses identified 18 sequences from the enriched cationic peptide fraction that showed the highest activity. Three novel peptides were identified via molecular docking, as potent ACE-inhibitors and binding was similar to that of the commercial drug captopril. Key binding characteristics included interaction with hydrophobic amino acids (Phe, Pro, Leu) near the C-terminal position and coordination with Zn (II) ions near the ACE active site.</p> <p>Immunological reactivity was measured by IgE-binding from shrimp-allergenic patient sera to antigens present within cricket peptides. Our studies demonstrate that immunoreactivity was impacted by enzymatic hydrolysis, depending on the conditions and heating source used. Tropomyosin (a major shrimp allergen) was extracted from both untreated crickets and protein hydrolysates, and verified as the major reactive protein. Tropomyosin reactivity decreased (under both partial and extensive hydrolysis) or retained (under conditions which prevented epitope cleavage). However, using microwave-assisted enzymatic hydrolysis was effective at decreasing tropomyosin reactivity in all immunoassays tested (IgG and IgE). Proteomic and immunoinformatic analyses revealed prominent allergen binding regions of cricket tropomyosin available for cleavage during enzymatic hydrolysis. Conserved antigen regions showed greater homology with other crustacean species, but not with other well studied allergenic insect proteins (i.e., cockroach). Lastly, LC-MS/MS and FT-Raman spectrometry suggests that reactivity was affected due to distinct epitope cleavage within the protein instead of decreased antigen extractability/solubility. </p> <p>The findings of this dissertation support that edible cricket proteins are a potential source of bioactive peptides for functional food or nutraceutical development. Additionally, using protein extraction methods such as microwave-assisted hydrolysis seems a promising tool for minimizing the immunoreactivity of the allergen present in this edible cricket species.</p>

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