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Browsing by Subject "Extrusion"

Now showing 1 - 6 of 6
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    Chemical Evaluation of the Apical Extrusion of Sodium Hypochlorite Using the Gentlewave® System
    (2019-08) Crepps, Joseph
    A critical component of the safety of an endodontic irrigation protocol is determining whether chemicals are extruded beyond the root canal space. Mandibular molars were suspended in distilled water. Teeth were irrigated with three different methods: side-vented needle irrigation, the GentleWave® system (GWS), and end-vented needle irrigation. The distilled water in which the teeth were suspended was collected and analyzed using spectrophotometry and a pH indicator. The estimated percentage of 3% NaOCl in the distilled water was significantly higher in the GWS compared to the side-vented needle irrigation group. These findings suggest the GWS causes extrusion of NaOCl beyond the apex of mandibular molars; these data also suggest the GWS causes an increased amount of apical extrusion of NaOCl compared to conventional side-vented needle irrigation.
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    The Effect of Size and Location of Composite Attachments on the Extrusive Force Delivered to a Maxillary Central Incisor by a Clear Aligner
    (2022-06) Slama, Zachary
    Introduction: One of the most challenging and least predictable tooth movements to achieve with clear aligner therapy is extrusion of maxillary central incisors. Composite attachments have been implemented to improve the biomechanical properties and make extrusion a more predictable tooth movement. Various attachment shapes have been investigated, but the effect of attachment size and location on the force delivered to a maxillary central incisor by a clear aligner has not been reported. Aim: To evaluate the effect of composite attachment size and location on the extrusive force delivered to a maxillary central incisor with a Zendura FLX clear aligner. Methods: Clear aligners designed to extrude a maxillary central incisor 0.25 mm using uLab software were fabricated using Zendura FLX .030 mil (0.75 mm) thickness clear aligner material. To evaluate the effect of attachment size, aligners were designed with three sizes of rectangular anterior extrusion attachments as well as no attachment. To evaluate the effect of attachment location, aligners were designed with a standard rectangular anterior extrusion attachment placed in the center of the facial surface of the crown, 2 mm apical, 2 mm incisal, in the center of the lingual surface of the crown and with no attachment. For each of the 9 groups, 5 aligners were fabricated with standardized margins trimmed 0.75 mm apical to the gingival margin. Extrusive force along the long axis of the crown was measured using a force gauge. Means and standard deviations were calculated and presented by group. The one-way analysis of variance (ANOVA) was conducted to compare the means between the groups and Tukey’s method was used as a post-hoc procedure for pairwise comparisons. P-values less than 0.05 were considered statistically significant. Results: Pairwise comparisons for all groups compared to No attachment were statistically significant (p <.0001). Pairwise comparisons for all attachment sizes were statistically significant (p < .0001). Although pairwise comparisons were statistically significant for the Incisal attachment group vs. Gingival attachment group (p = 0.033) and the Incisal attachment group vs. Mid-facial attachment group (p = 0.002), the observed differences may have been due to variation in aligner fabrication. No statistically significant differences were observed for pairwise comparisons of other attachment location groups. Conclusions: This is the first study in which the effect of attachment size and location on the extrusion of a maxillary central incisor with a clear aligner has been reported. In a benchtop model, all attachment configurations generated greater initial extrusive compared to the No attachment control. Attachment size has a positive relationship with initial extrusive force with larger attachments producing greater force. Attachment location did not appear to be as critical as attachment size in producing extrusive force. Biomechanically, larger attachments can be recommended to help generate the force required to predictably extrude maxillary incisors.
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    Impact of Processing on the Physicochemical and Nutritional Properties of Intermediate Wheatgrass (Thinopyrum intermedium) and Wheat (Triticum sp.)
    (2022-11) Boakye, Prince
    Annual cereal grains are a major part of the human diet. However, their cultivation is less sustainable and is associated with environmental issues such as soil erosion and emission of greenhouse gases into the atmosphere. Cultivating perennial grain crops to supplement these annual grains offers a promising approach to reducing these environmental issues while providing food for the ever-growing human population. To this end, intermediate wheatgrass (IWG), a perennial grain crop, is being developed and explored for mainstream food applications. The first part of this dissertation explored extrusion cooking of IWG for the first time to produce expanded IWG that could be used as snacks and breakfast cereals. First, we optimized the extrusion conditions for the production of expanded IWG. In that work, the effects of extrusion conditions including feed moisture content (20, 24, and 28%), screw speed (200, 300, and 400 rpm), and extrusion temperature (130, 150, and 170 °C) on the physical and functional properties (moisture content, expansion ratio, bulk density, hardness, water absorption index (WAI), water solubility index (WSI)) of IWG were investigated. Response surface methodology (RSM) was used to model and optimize the extrusion conditions to produce expanded IWG. The model coefficient of determination (R2) was high for all the responses (0.87 – 0.98). All the models were found to be significant (p < 0.05) and were validated with independent experiments. Generally, all the extrusion conditions were found to have significant effects on the IWG properties measured. Increasing screw speed and decreasing the extrusion temperature resulted in IWG extrudates with high expansion ratio. This also resulted in IWG extrudates with generally low hardness and bulk density. Screw speed was found to have the most significant effect on water absorption index (WAI) and water solubility index (WSI), with increasing screw speed resulting in a significant (p < 0.05) decrease in WAI and a significant (p < 0.05) increase in WSI. The optimum conditions for obtaining an IWG extrudate with a high expansion ratio and WAI were found to be 20% feed moisture, 200 – 356 rpm screw speed, and 130 – 154 °C extrusion temperature. Then, these optimum conditions were used to produce two expanded IWG products (extrudates I and II), and the physicochemical and nutritional properties of these products were characterized, comparing them to raw IWG flour. We observed that extrusion resulted in slight decreases in dietary fiber, fat, starch, and amylose contents of IWG, whereas protein and ash contents did not change. A significant increase in starch damage after extrusion led to significant increases in starch digestibility and hydration properties of IWG. Correspondingly, slowly digestible starches and resistant starches were significantly reduced after extrusion. Pasting profile studies showed significant decreases in all pasting parameters measured except for breakdown viscosity after extrusion. Higher antioxidant activity and phenolic acid levels, mainly due to ferulic acid, were observed even after extrusion. However, carotenoid content decreased significantly (up to 65.8% reduction in lutein and 50.4% reduction in zeaxanthin). These findings provide useful information on the production of expanded IWG using extrusion cooking. This is critical in the efforts to increase the demand and marketability of IWG. Furthermore, we have shown that extrusion cooking can improve the antioxidant activity and maintain high protein and dietary fiber levels in IWG, but it may not be suitable for preserving carotenoids in IWG.In the second part of this dissertation, we aimed to address an issue with the consumption of wheat, an annual grain that is a major staple worldwide. Wheat provides nearly 20% of calories and protein in the human diet. However, fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) and amylase/trypsin inhibitors (ATIs) present in wheat flour can trigger irritable bowel syndrome (IBS) and non-celiac wheat sensitivity (NCWS) symptoms in some individuals. This has negatively affected the demand and consumption of wheat in recent years. Thus, reducing FODMAPs and ATI concentrations in wheat flour could make the grain accessible to humans with IBS or NCWS. To this end, we first evaluated a diverse panel of heritage and modern spring wheat lines (208 lines in total) grown in two locations in Minnesota (Crookston and Saint Paul) for FODMAPs and ATI levels and carried out a genome-wide association analysis to identify markers associated with wheat FODMAPs and ATIs. The discovery of such markers, in conjunction with a genome-wide selection strategy, could aid in the selection of breeding lines with lower levels of FODMAPs and ATIs. FODMAPs and ATIs were quantified using High-performance anion-exchange chromatography (HPAEC) and High-performance liquid chromatography (HPLC), respectively. A strong population structure was observed, as the first principal component axis alone explained a third of the genotypic variation, and lines clustered into three distinct clusters of einkorn, emmer, and modern wheat lines. Trait correlations (r) were low to moderately high, ranging from 0.06 - 0.54. Broad-sense heritabilities ranged from low to medium (0.18 - 0.55). Association analysis resulted in the detection of 36 quantitative trait loci (QTL) in 15 chromosomes which were distributed in 30 unique genomic regions based on haplotype analysis; five of the 36 QTL were shared among two to four traits. The QTL were of small to medium effect as the range of explained phenotypic variation was 6.4% - 10.5%. There was no overlap among the QTL regions reported in this research compared with those reported in previously published studies. Genomic prediction models predicted the traits with low to moderately strong correlations (r = 0.23 - 0.49). We also investigated the effect of type I sourdough fermentation (4- and 12-h fermentation times) on the FODMAP and ATI levels in twenty-two wheat lines selected from the lines used in the genetics study based on availability and the initial levels of these compounds. We observed that FODMAPs and ATIs were significantly influenced by variety as well as growing location. Longer sourdough fermentation time (12 h) caused up to 69%, 69%, and 41% reductions in fructans, raffinose, and ATIs, respectively, in the resulting sourdoughs. However, a substantial increase in mannitol (550%) was observed after sourdough fermentation. These findings suggest that in type I sourdough fermentation, mannitol production should be monitored, and strategies to reduce its level in the fermented product should be considered.
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    Interfacial coupling between immiscible polymers: flow accelerates reaction and improves adhesion.
    (2011-10) Song, Jie
    As the workhorses of the plastics industry, polyolefins are consumed in the largest volume of all types of polymers. Despite their wide use, polyolefins suffer from poor adhesion and compatibility with other polar polymers due to their intrinsic low polarity and lack of functional groups. The first goal of this study is to enhance interfacial adhesion between polyolefins with other polymers through coupling reaction of functional polymers. We have used functional polyethylenes with maleic anhydride, hydroxyl, primary and secondary amino groups grafted through reactive extrusion. Functional polyolefins dramatically improved the performance of polyolefins, including adhesion, compatibility, hardness and scratch resistance, and greatly expand their applications. The second goal is to understand the factors affecting adhesion. We systematically investigated two categories of parameters. One is molecular: the type and incorporation level of functional groups. The other is processing condition: die design in extruders, reaction time and temperature. The interfacial adhesion was measured with the asymmetric dual cantilever beam test and T-peel test. The extent of reaction was quantified through measuring anchored copolymers via X-ray photoelectron spectroscopy. A quantitative correlation between adhesion and coupling reaction was developed. A coextruded bilayer system with coupling reaction at interfaces was created to clarify processing effects on the kinetics of coupling reactions. For the reaction between maleic anhydride modified polyethylene and nylon 6, the reaction rate during coextrusion through a fishtail die with compressive/extensional flow was strikingly almost two orders of magnitude larger than that through a constant thickness die without compressive flow. The latter reaction rate was close to that of quiescent lamination. We attribute the reaction acceleration through the fishtail die to the large deformation rate under the compressive/extensional flow condition. The deformation generated stretched chains leading to complimentary functional groups exposed to each other and forcing reactive species to overcome the interfacial diffusion barrier. We also found reaction acceleration through a fishtail die for the coupling of functional PE with thermoplastic polyurethane. This work illustrates that enhancing the compressive/extensional flow during polymer processing may create opportunities for increasing adhesion and designing new reactions and products.
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    Investigation of Purification of Oligosaccharides Produced Using Twin-Screw Extrusion
    (2021-01) Monsefi Parapari, Ghazal
    Lactose, a low value dairy product, was polymerized to a soluble dietary fiber called polylactose using twin-screw extrusion. Non- enzymatic browning reactions occurring during extrusion produce colored compounds and hydroxymethylfurfural. Thisresearch focuses on development and optimization of a purification method for polylactose using activated carbon and resins. Polylactose was ground, solubilized in water at three different concentrations (50 mg/mL, 100 mg/mL and 150 mg/mL). Forty mL of polylactose solution was flowed through the filtration system utilizing gravity. The filtration system was rinsed with 20 mL double distilled water. The rinse water plus the filtrate collected were freeze dried to achieve a powder form suitable for different analysis. 42.4% Purolite A874 resin followed by 42.4% Activated carbon and 3% diatomaceous earth was proven to have the best purification results increasing dietary fiber content from 54.48% to 92.24% while reducing the hydroxymethylfurfural content by 90.91% to a level that was lower than the maximum level determined by the Joint FAO/WHO Expert Committee on Food Additives HMF limit in polydextrose (0.1%). Furthermore, the effect of polylactose solution concentration for filtering 40 mL polylactose solution was determined. Using 50 mg/mL concentration achieved the highest dietary fiber content. This could be since less polylactose had to interact with the same amount of filtration material resulting in removing more impurities and caramelization products. However, the hydroxymethylfurfural content reduction was the same for 50 mg/mL and 100 mg/mL concentrations.
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    Storage Stability of Intermediate Wheatgrass (Thinopyrum Intermedium) Flour as Impacted by Agronomic Practices, Breeding, and Commercial Germination and Extrusion Techniques
    (2023-10) Loehr, Leslie
    Intermediate wheatgrass (IWG, Thinopyrum intermedium) is a perennial cereal grain capable of aiding the agricultural community in reducing the global environmental detriments of commercial agricultural practices. Factors such as soil erosion, lack of carbon sequestration, and nitrogen leaching are all current issues that need to be addressed with IWG potentially providing a sustainable solution. In addition to its environmental benefits, IWG provides ample nutritional advantages such as a relatively high protein, dietary fiber, and antioxidant content compared to one of the most ubiquitous cereal grains globally: wheat. However, a lack of understanding regarding on-going breeding program progress coupled with the absence of data on the storage stability post-processing of IWG grains contributes to little incentive for producers, processors, and consumers to focus on switching to this sustainable grain. Therefore, the objectives of this study were to: (1) screen 11 lines of IWG for differences in composition and enzyme activity as affected by breeding and agronomic practices, (2) determine the compounded impact of fat content, enzyme activity, and antioxidant content and activity on the storage stability of novel IWG cultivars and (3) identify the chemical changes induced by extrusion and germination of IWG grains and their impact on the storage stability of whole flours. Prior to treatment and storage, 11 samples of IWG were analyzed for proximate composition, protein profile, starch and total dietary fiber content, antioxidant content and activity, and enzyme activity utilizing AOAC and AACC standard methods. These results, primarily antioxidant content and activity, fat content, and enzyme activity, informed the selection of samples to be subjected to extrusion and germination treatments and subsequent ambient storage. Once selected, these samples underwent commonly used procedures for both extrusion and germination of cereal grains. Post-treatment and milling into whole flour, the samples were subjected to storage and analyzed periodically for carotenoid and hydroxycinnamic acid (HCA) content using high performance liquid chromatography, antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and leucomethylene blue (LMB) assays (all at 0, 1, 3, 6, and 8 months of storage), lipase and lipoxygenase enzyme activity via a copper soap assay and ferrous oxidation-xylenol orange (FOX) assay, respectively (at 0, 3, 6, and 8 months of storage), free fatty acids and peroxide value content via AOAC titration methods (940.28 and 965.33, respectively; both at 0, 1, 3, 6, and 8 months of storage), and volatile odor compounds (VOC) via dynamic purge-and-trap followed by gas chromatography coupled with olfactometry and mass spectrometry analysis (GC-O-MS) at 0, 3, and 8 months of storage). The first commercial cultivar and the new IWG varieties continue to hold a strong nutritional advantage over hard red wheat (HRW), and all samples also contained relatively higher ferulic acid and lutein contents and had high antioxidant activity. Additionally, protein and total dietary fiber content was higher in IWG than in HRW. Variance among the samples was more strongly linked to genetic makeup rather than geographic growing location, confirming promise for individual cultivars to perform similarly regardless of agronomic effects. Based on their fat content, enzyme activity and antioxidant profile, MN1601-SYN2, MN1603-SYN3, and MN-Clearwater varieties were selected for extrusion and germination processing followed by 8 months of ambient storage. Extrusion caused complete inactivation of lipase activity, while germinated samples retained their lipase activity. Lipase activity was determined to be more influential to hydrolytic rancidity than fat content alone, giving an advantage to the extrusion process. The abundantly present antioxidants combated oxidative rancidity, with carotenoids playing a major role, as evidenced by the significant (P < 0.05) loss in lutein and zeaxanthin between 3-6 months of storage. This observed loss occurred at the same time as FFAs, PV, and VOC (primarily hexanal and 2-pentyl-furan) experienced abrupt increases. These findings are quite insightful for future IWG breeding progress. In addition, the work provided a comprehensive understanding of how common post-harvest processing affects the storage stability of IWG flour, an essential information to promote its use as a food ingredient.