The objective of this study was to improve canola protein gelation properties with the use of enzymes. Both cross-linking and limited proteolysis were explored. Enzyme treatments were performed prior to heat induced gelation. A texture analyzer, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy were used to characterize the resulting networks. Enzymatic cross-linking with transglutaminase was shown to improve the gelation of canola protein isolate (CPI). To the contrary, proteolysis with trypsin, ficin and bromelin, did not enhance the gelation properties of CPI.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 91-109). Also available on the World Wide Web.

Thesis (Ph.D.). / Written for the Dept. of Food Science and Agricultural Chemistry. Title from title page of PDF (viewed 2009/06/05). Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Sept. 12, 2006). PDF text of dissertation: xi, 207 p. : ill. ; 10.65Mb. UMI publication number: AAT 3208078. Includes bibliographical references. Also available in microfilm, microfiche and paper format.

In recent years, the application of microparticles in different fields including cosmetics, agriculture, pharmaceutics and biomedicine has been widely investigated.In this project, we aimed to improve the preparative methods for chitosan–triphosphate microparticles (Cs/TPP) for perspective application in the fields of cell encapsulation and controlled drug delivery. Prior to the preparation of chitosan-based microparticles, in order to confirm good biocompatibility and reproducibility, protocols have been established for the purification and characterisation of chitosan including the assessment of average molecular weight, protein content and degree of deacetylation.This study then primarily focused on the use of β-glycerophosphate (βGP) as an excipient, which is known to solubilize chitosan at neutral pH, thus allowing the preparation of chitosan microparticles (microspheres and toroidal) via ionotropic gelation under physiological conditions. The preparation of Cs-βGP/TPP microparticles was optimized varying several key process variables (concentration, flow rate, and frequency) and these microparticles were produced with a narrow size distribution (400 – 500 μm, spherical shape) and compared to Cs/TPP controls. The main result was the possibility to perform this process at neutral pH, although we have also demonstrated an improved toughness and cross-linking density of these microspheres as a result of the presence of β-glycerophosphate. Further, we have investigated the application of this method to a toroidal geometry, which provides advantages in terms of better transfer of oxygen and nutrients to any encapsulated materials. Cs/TPP and Cs-βGP/TPP ‘micro-doughnuts’ were also prepared and characterised. This research highlighted the evidence of a higher cross-linking density of these microparticles in comparsion with the spherical ones. In order to optimise the physicochemical characteristics of these microparticles for future applications as biomaterials, the surface of Cs/TPP and Cs-βGP/TPP microparticles was modified through an additional polyelectrolyte complexation with poly (sodium 4- styrene sulphonate) (PSS). The improved toughness and cross-linking density was confirmed by measuring the mechanical properties and solid content which indicated the successful complexation of PSS onto the surface of these microparticles.

The purpose of this experiment is to study as a model the gelation phase transition of agarose solutions with transverse relaxation (T2) quantitative magnetic resonance imaging (qMRI). The focus is on the reduction of T2 of agarose solution upon gelation. The sol-to-gel phase transition of agarose may provide a useful and controllable experimental model of tissue formation. Furthermore, it may provide the basis for exact mathematical models useful for understanding the much reduced transverse relaxation times (T2) observed in solid tissues relative to simple liquids. In this context, the purpose of this work was to monitor dynamically with T2 quantitative MRI the liquid-to-gel phase transition of pure agarose as a function of gel concentration. Samples of agarose at various concentrations were allowed to cool down while scanning dynamically with T2 qMRI, 32 x 10milliseconds (ms) echoes, CarrPurcell-Meiboom-Gill (CPMG), 3Tesla.T2 versus; (temperature).curves of each agarose solution show a distinct phase transition region characterized by a sharp T2 reduction. Four agarose solutions were sequentially prepared by dissolving agarose powder in distilled water at concentrations of 1%, 2%, 3%, and 4% by weight/volume. Immediately after preparation and boiling at 98°C, each liquid agarose solution was poured into a plastic container and scanned dynamically at 3.0T as it cooled down with a whole body MRI scanner (Achieva, Philips Medical Systems, Cleveland, OH). A single axial slice multi spin echo CPMG pulse sequence with the following parameters was used: 32 echoes, 10ms echo spacing, 1.5s repetition time (TR), 160 x 160 matrix size, and 2 SENSE factor. The time per dynamic scan was 1minute. The DICOM images were further processed with an adaptive T2 qMRI algorithm programed in Mathcad (Parametric Technology Corporation, Needham, MA) whereby the number of echoes used in the semi-logarithmic linear regression varies automatically from pixel to pixel depending on noise level. The T2 values of agarose gels have been measured during the entire gelation phase transition process at four different concentrations. The T2 versus time (temperature) curves of all the four concentrations shows a rapid drop at about 24 minutes (T~40°C) at which time the gelation phase transition begins. At all temperatures, T2 decreases as a function of increasing agarose concentration. The data shows similar behaviors for all concentrations with a phase transition characterized by a drastic drop in T2 occurring while the temperature drops by approximately 8°C. These results may be useful for testing theoretical models of the Nuclear Magnetic Resonance (NMR) T2 relaxation properties during tissue formation. Quantitative magnetic resonance imaging (qMRI) differs sharply from conventional directly acquired MRI in that objective measures [such as the trio of the basis MR properties: longitudinal relaxation (T1), T2 and Proton Density (PD)] are used for analysis as well as further post-processing rather than relative signal intensities. Q-MRI portrays the spatial distribution of absolute biophysical parameter measurements on a pixel-by-pixel basis; Kevin J. Chang et al 2005

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This thesis is an experimental investigation of phase behavior, crystallization, gelation and phase separation kinetics of polymer solutions in dense fluids at high pressures. The miscibility and dynamics of phase separation were investigated in solutions of atactic polystyrene with low polydispersity (Mw = 129,200; PDI = 1.02) in acetone. Controlled pressure quench experiments were conducted at different polymer concentrations to determine both the binodal and the spinodal envelops using time- and angle resolved light scattering techniques. At each concentration, a series of rapid pressure quenches with different penetration depths in a range from 0.1 MPa to 3 MPa were imposed and the time evolution of the angular distribution of the scattered light intensities was monitored. The solution with 11.4 wt % polymer concentration underwent phase separation by spinodal decomposition mechanism for both shallow and deep quenches. Below this critical polymer concentration, phase separation was found to proceed by nucleation and growth mechanism for shallow quenches, but by spinodal decomposition for deeper quenches. Gelation and crystallization processes and the influence of pressure and the fluid [Cho et al. 1993]composition were investigated in solutions of poly(4-methyl-1-pentene) [P4MP1] in n-pentane + CO₂ and in solutions of syndiotactic polystyrene [sPS] in toluene + CO₂, and also in acetophenone + CO₂ fluid mixtures over a pressure range up to 55 MPa and carbon dioxide levels up to 50 wt %. In pure pentane, P4MP1 undergoes crystallization and leads to Form III polymorph at low pressures, but to Form II at high pressures. In n-pentane + CO₂ mixture fluids, the polymorphic state changes from a mixture of Forms III and II to Form II and eventually to Form I with increasing CO₂ content. High level of carbon dioxide (≥40 wt %) in the solution was found to lead to gelation instead of crystallization. No liquid-liquid phase boundaries could be observed in any of the P4MP1 solutions. In contrast to P4MP1 in n-pentane, syndiotactic polystyrene was found to undergo gelation in toluene or acetophenone forming a polymer-solvent compound with the δ crystal form. Also in contrast to P4MP1 systems, addition of carbon dioxide to sPS solutions alters the process from that of gelation to crystallization leading to the β crystal form. In solutions with high CO₂ level, in addition to the gelation or crystallization boundaries, a liquid-liquid phase separation boundary was also observed. The phase separation path followed was found to influence the eventual morphology and the crystal state of the polymer. In sPS solutions in toluene + CO₂, if the sol-gel boundary were crossed first by cooling the solution at a fixed pressure, the resulting morphology was found to be fibrillar and the polymer displayed the δ crystal form. If instead, the liquid—liquid phase boundary were crossed first by reducing pressure at a fixed temperature, the polymer-rich phase leads to a stacked-lamellar morphology with the β crystal form while the polymer-lean phase leads to a mixed morphology with lamellar layers connected by fibrils with the polymer displaying δ + β crystal forms. In solutions in acetophenone + carbon dioxide, when the gelation boundary is crossed first, the resulting structure is the δ form as in the toluene + CO₂ case. At comparable CO₂ levels, when the L-L phase boundary is crossed first, in the acetophenone system, polymer-rich phase was found to generate a mixture of δ + β forms while only the δ form was found in the polymer-lean phase, in contrast to the observations in the toluene + CO₂ systems. Based on crystallographic, spectral and microscopic data, a thermodynamic framework was developed which provides a mechanistic account for the formation of the different polymorphs. / Ph. D.