The aim of this work was to analyse the effect of bacterial cellulose fibrils (BCF) on the gelatinization profile and pasting properties of starches from different sources (wheat, maize and waxy maize) and amylose contents. Blends of 8% starch with different BCF levels (0, 0.5, 2, 6 and 10% based on the dry weight of starch) were prepared and tested by Rapid Visco-Analysis (RVA), Differential Scanning Calorimetry (DSC) and both Optical and Polarized Light Microscopy.Results showed that BCF produce a significant modification of pasting properties.The pasting temperature was reduced but viscosities (peak, final, trough, breakdown and final) increased. The reduction in pasting temperature at the highest BCF addition was 20 0 C higher for maize and wheat starches but only 2 0 C higher for waxy maize starch. In contrast to the pasting temperature, the gelatinisation temperature by DSC for all three starches slightly varied upon BCF addition, but the gelatinisation enthalpy was reduced to a greater extent than values reported for the addition of other hydrocolloids to starch blends. Optical and polarized light microscopy showed the presence of domains rich in starch and highly aggregated BCF in all three starches evaluated. The increase in viscosity and decrease in pasting temperature are discussed in terms of changes in starch concentrations in the starch rich domain. These results open interesting perspectives in the use of bacterial cellulose and plant cell walls to design novel bio-composites to structure foods.
Some effects of NaOH treatment at concentrations of up to 8 M on (1) the porous structure, (2) the degree of swelling, (3) carboxyl content using methylene blue sorption and 9H-fluoren-2-yl-diazomethane (FDAM) methods, (4) dyeing, (5) the molecular weight distribution measured by gel permeation chromatography (GPC), (6) crystallinity determined by wide angle X-ray diffraction (WAXD) and (7) the tensile properties of lyocell fibers were investigated. The porous structure of fibers was visualised using fluorescence microscopy and transmission electron microscopy (TEM) on fiber cross-sections and was also studied by inversion size exclusion chromatography (ISEC). Mean pore diameter and pore area of fibers were not changed by NaOH treatments. The pore volume increased above 2.5 M NaOH. NaOH-treated samples showed higher dye uptake, higher swelling, but lower carboxyl and moisture content and increased crystallinity. As the NaOH concentration increased, the depth of colour following dyeing with C.I. Direct Red 81 also increased due to deep penetration of alkali into the fiber. In general, fiber properties were distinctly different in the ranges 0 to approximately 3 and 3-8 M NaOH.
a b s t r a c tHeavy oil and bitumen are a potential alternative energy source to conventional light crude. However, recovery of these resources can have substantial environmental impact. Downhole upgrading offers the prospect of both improving recovery, and decreasing environmental impact. However, use of catalysts to enhance downhole upgrading is limited by the need for one that can survive the extreme coking conditions arising from the cracking of heavy oil. In this work the potential of hydrogen donors to improve upgrading and enhance catalyst lifetime was considered. In order to extract detailed information on the catalyst structural evolution during reaction a novel parallel adsorption and thermoporometry characterization method was used. This technique allows detailed information to be obtained on the spatial juxtaposition of different pores, and their relative connectivity, as well as on size distributions. For catalyst operated at the conditions studied, it has been found that coking arises in smaller pores branching off the larger pores providing access to the catalyst interior. It has been found that while coking following use of different types of hydrogen donor leads to similar primary patterns of evolution in the pore-scale descriptors of the remaining accessible void-space, differences do arise in the overall accessible volume. Hence, it seems the hydrogen donor affects the location rather than general nature of the pore structure changes. However, at a secondary level of scrutiny, some differences in porescale evolution are also identified for different hydrogen donors. These differences identified helped the understanding of variations in the performance of different hydrogen donor and catalyst combinations.
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