Thesis (doctoral)--Universidad Autónoma de Barcelona, 1973.

Thesis (M. Sc.)(Geology)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

The nutty and cereal aromas of new make malt whisky are important sensory characteristics of certain distillery malts of commercial value for blending; however there is a lack of understanding regarding the volatile congeners which contribute to these complex sensory characters. The work described in this thesis aimed to improve knowledge of the chemical origins of nutty and cereal aromas in immature spirit in order to aid process control of these characters during manufacturing. Two aroma extraction methods were compared; liquid-liquid extraction (LLE) using dichloromethane and solid-phase extraction (SPE) with LiChrolut EN sorbent. New make spirit samples from industry (n=S) were evaluated by a trained whisky sensory panel using Quantitative Descriptive Analysis (QDA). Four were noted for their nutty/cereal character, the other served as a non-nutty control. Gas Chromatography-Olfactometry/ Mass Spectrometry (GC-O/MS) was used to try and identify compounds in chromatogram regions coincident with nutty/cereal descriptors. Using LLE extracts, 14 such regions were identified. LiChrolut EN SPE proved to be more selective (19 nutty/cereal odour active regions). 2,S-dimethylpyrazine (known to impart a nutty/cereal character in other food systems) was one noted congener, which was only detected using the more selective SPE method. The gross volatile compositions of the 5 spirit samples were remarkably similar, suggesting that congeners present at low concentration but with low odour thresholds are likely responsible for nutty/ cereal characters. One analytical difference of note was that the nuttier samples contained higher concentrations of long-chain esters. Thus, ethanolic Atmospheric Pressure Chemical Ionisation Mass Spectrometry (APCI-MS) was used to analyse the headspace concentrations of a test set of 14 whisky aroma volatiles above a series of aqueous ethanolic solutions differing in concentrations of alcohol (5 -40% ABV) and ethyl hexadecanoate (O-SOO mg/L). Ethanol had a significant solubilising effect (p < 0.0001) on headspace volatile concentrations of all the aroma compounds, whilst the ethyl hexadecanoate concentration had a selective effect of reducing headspace concentrations of the more hydrophobic aroma compounds (Log P > 2.S). We propose that nutty and cereal characters are imparted by relatively polar aroma compounds, whose characters are emphasised by the selective incorporation of hydrophobic aroma compounds into the interior of micelle-like structures formed by long chain esters (typified here by ethyl hexadecanoate). Some distillers have reported that manipulation of the lipid concentrations in wash offers a method of controlling the nutty/oily character of new make spirit. A batch of fermented wash sourced from industry was spiked with varying concentrations of oleic (18:1) and linoleic (18:2) acids and (laboratory) distilled at two different temperatures, using a D-optimal experimental design to evaluate the impacts of each factor. Nutty (p = 0.0203) and oily (p = 0.0034) aroma characteristics were scored as significantly stronger in distillates of wash spiked with 100 Ilg/mL each of oleic and linoleic acids, as compared to the control. GC-O/MS of distillate extracts once again determined several odour active regions relevant to the nutty/cereal characters and concentrations of some compounds could be correlated with nutty/cereal QDA scores. New make spirit samples from 35 individual malt whisky distilleries were extracted using the LiChrolut SPE method and analysed by GC-MS. Analytical concentrations of 'candidate' nutty-cereal compounds (n = 20) were used to model sensory QDA data for the 35 spirit samples (nutty, oily, cereal and feinty characters) using Principal Components Analysis (PCA). Significant positive correlations with nutty were seen for 7 compounds (using ANOVA). These included the Maillard products 2-furanmethanol (p < 0.0001), 2-methylpyrazine (p < 0.0013) and 2,5-dimethylpyrazine (p < 0.0004). The PCA overlay bi -plot showed clustering of certain higher alcohols near to the nutty aroma descriptor (methionol, pentan-1-0I, 2-phenyethyl alcohol). Nutty and cereal characters of whisky are of complex origin and likely originate from multiple congeners in a synergistic mixture. This work has shown that processes of particular importance to the expression of this character in new make spirit are lipid oxidation and Maillard chemistry. The conditions for these reactions are to be found during malt kilning and distillation. Whilst these processes are where nutty/cereal compounds are likely to be formed, other distillery parameters such as the mashing protocol, length of fermentation (both determine the supply of key precursors such as fatty and amino acids) and the spirit cut of the distillation govern the chemical composition of the final spirit.

In recent decades, scientific research giving more attention to the development of bio-based polymer composites due to the extensive usage of petroleum based fillers as well as polymer matrices for the generation of polymer composites. It is a well-known fact that the petroleum derived polymer composites raise inevitable issues such as environmental pollution, waste management and depletion of petroleum resources etc. So it is important to develop fully or partially biodegradable polymer composites without compromising the mechanical, physical and thermal properties which are required for the end use applications. In this investigation, two different types of filler materials such as sisal fibres and halloysite nanotubes were used to prepare PLA polymer composites and their morphology, physical, mechanical, dynamic mechanical, thermal, water absorption and biodegradable properties were studied. This work also involves the preparation and properties of polypropylene composites reinforced with sisal fibres and halloysite nanotubes to compare the mechanical and thermal properties with PLA composites. First, surface treatment was performed for sisal fibres in order to remove the amorphous materials such as hemicellulose, lignin and pectin from the surface of the fibres which enhances the fibre-matrix interfacial strength and mechanical properties of the fibres and their polymer composites. Sisal fibres were subjected to different surface treatments such as alkali, high intensity ultrasound (HIU), and the combination of alkali and HIU and their effects on the morphology, fibre diameter, moisture absorption, mechanical and thermal properties of untreated and surface treated sisal fibres were studied. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM) results confirmed the removal of amorphous materials after the combined treatments of alkali and ultrasound. Moisture absorption and diameter of the sisal fibres were significantly reduced by 40 and 200% respectively after the combination of alkali and HIU treatment as compared to untreated sisal fibres. TGA results revealed that the thermal stability of sisal fibres obtained with the combination of alkali and HIU treatment significantly increased by 38.5 oC as compared to the untreated fibres. Tensile properties of single fibre showed a reduction in the tensile strength and modulus by 25% and 26% respectively as compared to the untreated sisal fibre owing to surface treatments. A reduction in the tensile properties is mainly due to the removal of amorphous materials from the surface of sisal fibres which act as binding materials for cellulose. Second, the effect of different surface treatments on the morphology, mechanical, thermal, water absorption and biodegradable properties of sisal fibres reinforced PLA (SF/PLA) composites has been investigated. For this, different ratio of untreated and surface treated sisal fibres was mixed with PLA polymer matrix by using an internal mixer. Compounded materials from the internal mixer were subjected to compression moulding to prepare the test specimens. FE-SEM analysis confirmed the good dispersion of different surface treated SF in the PLA composites. The tensile strength and modulus increased by 10 and 75.4% for 15 wt% and 30 wt% of fibre loading respectively with the combined treatment of alkali and HIU PLA composites as compared to the untreated fibre reinforced PLA composites. Young’s modulus of the composites has also been predicted by using the theoretical models which fit well to the obtained experimental values. Dynamic-mechanical analysis (DMA) revealed that the combination of alkali and HIU treated SF/PLA composites showed an increase in the storage modulus by 15% and 30% as compared to the untreated fibre composites and pure PLA respectively. TGA and DSC analysis revealed that the thermal stability and crystallinity increased significantly for the PLA composites reinforced with sisal fibres of combined treatment of alkali and HIU. Water absorption study showed a considerable reduction in the water absorption and coefficient of diffusion by 136% and 130% respectively for the combination of alkali and HIU treated SF/PLA composites as compared to untreated SF/PLA composites. The degradation of SF/PLA composites was studied by composting the samples into the soil. A significant weight loss of 17.87% could be observed for the addition of 30 wt% of untreated SF/PLA composites after soil composting for 120 days. Apart from sisal fibres, halloysite (Hal) nanotubes were also used as reinforcement fillers to study their effectiveness in improving the mechanical and thermal properties of PLA nanocomposites. Hal nanotubes were surface modified with 3-aminopropyltriethoxysilane (APTES) to enhance the surface interaction of Hal nanotubes with PLA and to achieve good dispersion of Hal nanotubes across the PLA matrix. Nitrogen adsorption-desorption, FTIR and TGA analysis results were confirmed the successful modification of Hal nanotubes surface with APTES. The different wt% of unmodified and APTES modified Hal-PLA nanocomposites were prepared by using internal mixer and compression moulding machine. The resultant Hal-PLA nanocomposites were characterized for their morphology, thermal, mechanical and dynamic-mechanical properties. Tensile strength increased to 62.6 MPa with the addition of 4 wt% of APTES modified Hal-PLA nanocomposites which is 26.5% higher than pure PLA and 15% higher than unmodified (4 wt%) Hal-PLA nanocomposites. Impact strength of 4 wt% APTES modified Hal-PLA nanocomposites increased by 20% and 40% as compared to unmodified Hal-PLA nanocomposites and the pure PLA respectively. TGA analysis revealed that the thermal stability increased significantly by 17 oC with the addition of 4 wt % of APTES modified Hal nanotubes onto PLA. Storage modulus increased by more than 10% with the addition of 4 wt% of APTES modified Hal nanotubes as compared to pure PLA. To compare the PLA composites with conventional polymer matrix composites, composites of polypropylene (PP) were prepared by reinforcing with sisal fibres and Hal nanotubes and the effect of surface treatment of sisal fibres and surface modification of Hal nanotubes on the mechanical and thermal properties of SF/PP and Hal-PP nanocomposites were studied. Tensile properties were increased for the combined treated SF/PP composites as compared to the untreated and pure PP. Tensile modulus and strength increased by more than 50% and 10% respectively as compared to the untreated SF/PP composites. TGA and DSC results revealed that the combination of alkali and HIU treatments increased the thermal stability and crystallinity by 8 oC and 8% respectively as compared to untreated SF/PP composites. DMA analysis confirmed the significant enhancement of storage modulus for the combined treated SF/PP composites by 50% as compared to pure PP. Mechanical and thermal properties were studied for unmodified and APTES modified Hal nanotubes reinforced PP nanocomposites. The investigations suggest that the mechanical properties of APTES modified Hal-PP nanocomposites were found to be superior to the unmodified Hal-PP nanocomposites. The tensile strength and modulus increased by 31 and 72% with the addition of 6 wt% of APTES modified Hal-PP nanocomposites as compared to pure PP. Impact strength also increased by 44% than pure PP with 6 wt% loading of APTES modified Hal nanotubes. Thermal analysis revealed that the thermal stability and percentage crystallinity increased by 15 oC and 22% respectively for the Hal-PP nanocomposites with surface modification by APTES. DMA analysis shows the improved storage modulus by 28% as compared to pure PP. Based on the present work, it can be said that the sisal fibres and Hal nanotubes have potential as reinforcing materials in the generation of fully bio-based polymer composites. / However, surface treatments and/or modification were playing an important role in order to tune the required mechanical and thermal properties of the polymer composites. This study also proved that in comparison to the conventional polymer matrix materials such as PP, PLA is a strong competitor with respect to its good mechanical properties and improved thermal stability apart from the fact that PLA is one of the best known biodegradable and biocompatible polymer matrices in the current market to use not only in medical application, but also in various commercial applications such as packaging, automotive and home appliances.

The titanium alloy Ti-6Al-4V has been favoured by the aerospace industry for the past several decades due to its good combination of specific mechanical properties, alongside corrosion and fatigue resistance. Titanium alloys are naturally suited to the near net shape processing technique of Additive Manufacture (AM) due to both the inherent high cost of the raw materials, and the difficulties associated with machining the alloys. Unfortunately, the combination of Ti-6Al-4V with AM has been found to lead to undesirable microstructures with respect to large columnar prior β grains being found to grow potentially across the entire height of builds. This microstructure has been shown to lead to property anisotropy and poor fatigue resistance. However, it has recently been found that the integration of an additional process step that lightly deforms the deposited material between added layers leads to the refinement of this undesirable microstructure. This work characterises the effect that two different deformation processing techniques have on two different additive manufacturing processes; the effect of peening on a laser-powder AM technique, and the effect of rolling on an electric arc-wire AM technique. In both cases far more randomly textured prior β grains were found with an average grain size of > 100 µm rather than mm long columnar grains with a common growth direction formed in the non-deformed builds. The refined β microstructure was found to lead to a reduction in texture of the room temperature alpha phase. The low stains involved (>10%) indicated that the refined grain structures did not form by traditional recrystallisation mechanisms. In-situ EBSD measurements at temperatures spanning the alpha → β phase transformation have been used to observe the growth of new β orientations from crystallographic twins in the deformed microstructure that may explain the origin of the refined grains. New β orientations were observed to grow from twinned alpha colonies and from between alpha laths, where the new β is found to grow sharing a twinning relationship with the residual β. Simulation of both of the individual processing steps under laboratory conditions has been found to successfully replicate the refinement observed in process. Orientation analysis suggests that twinning of the residual β could lead to the texture observed in the refined grains. It is therefore suggested that the refined grains are formed from β twinned regions in the deformed material growing under the alpha → β phase transformation, as the material is heated by the next added layer during AM.

The analysis of innovation contained in this thesis differs considerably in both scope and aims from most analyses of innovation. It is important to discuss why the approach taken has been adopted, and to justify its usefulness. There is no absence of analyses of innovation and associated invention. Individual inventions have been examined, notedly by Jewkes and his co-authors (1); analyses have been made of innovation in selected industries, and this has been related to international trade in these industries (2); the detailed antecedents of individual technological innovations have been traced back in time, both for weapon systems and for civilian products (3); the spread of important new techniques, normally associated with large-scale capital investment, has been analysed (4). Much of this work has been done, either directly or indirectly, to answer specific questions of science policy, and these works have been influential factors in the formulation of science policy. The questions which may be answered by such approaches are important. Is money aimed at producing inventions (and, by implication at least, innovation) best invested in establishing large research centres, or in encouraging with suitable fiscal measures individual inventors (5)? What is the relationship between the concentration of an industry and its propensity to innovate? Should government finance be concentrated in closely targetted contracts, or in university research? What should the government attitude be towards industries, such as the pharmaceuticals industry, in which successful products enjoy what may appear super-normal profits while overall heavy research expenditure is incurred (6)?

This work reports a fundamental study of the science and economics of microwave and RF drying of foods, addressing current knowledge gaps and introducing new techniques to aid the development of new microwave and RF drying processes. The present study has discovered that a correlation exists between the points of inflection of the moisture dependant dielectric properties and the moisture dependant water activity. Hence the moisture dependant dielectric properties are governed by the state of the water as defined by the sorption isotherms. Water activity equations were mathematically modified in this study to successfully describe moisture dependant dielectric properties. This is a valuable contribution to science as there are currently no recognised standard equations for describing the moisture dependence of dielectric properties. These new proposed equations are of great value as they can be used in microwave drying models. This will enable engineers to optimise microwave and RF processes, leading to a reduction in the trial and error approach that currently prevails in industry. Improved optimisation may ultimately lead to more successful microwave and RF applications. It is extremely important to be able to monitor key parameters such as porosity, oil and water content, when introducing a new food processing technique. To this end, a new and novel technique for quantifying the porosity of thin irregularly shaped food has been established. This can be used as a diagnostic tool to assess and optimise processing changes such as the introduction of new microwave or RF drying processes. A good understanding of how RF/MW processes affects porosity can be used to optimise the drying process, leading to a greater probability of success. Sorption isotherm measurements carried out in this study showed that the gelatinisation of starch in potato has a negligible effect on the isosteric heat of sorption. This is important for drying applications, as the isosteric heat of sorption is very significant compared to the latent heat at low moisture contents. Dielectric properties were measured for potato crisps, biscuits, and pasta particulate at 915MHz, and were used to gain new insights into moisture levelling behaviour through analytical analysis. Contrary to common belief, it was found that moisture levelling can be more effective below the critical moisture content, at lower moisture contents. Although moisture levelling limits the variability of the final moisture content, it was found that fine control of the final moisture content can only be achieved by minimising variation in electric field exposure. Feasibility studies of microwave applications showed that finish drying microwave applications were far more practical and cost effective compared to applications that have to remove large quantities of water. Dry food is generally quite thin so that it is eatable, or for rehydration purposes. As a consequence conventional food drying processes tend to be sufficiently energy efficient so that even microwave and RF finish drying processes are comparatively expensive with respect to energy usage. Hence, microwave and RF food drying must be justified by improvements in quality.

Whilst there is a tradition of indigenous opaque sorghum beer production in Africa, the manufacture of Western-style clarified lager beers from sorghum is a relatively recent development, originating in late 1980’s Nigeria. There remains substantial scope to optimise the process by tailoring the equipment and conditions utilised more specifically to the raw material. This was the context to the main objectives of this PhD project: towards an improved sorghum brewing process. Two principal approaches were employed: 1. The reduction of primary energy usage by developing novel modifications to the mashing and wort boiling unit operations and 2. Characterisation of the material properties of a substantial co-product of sorghum brewing, sorghum spent grains (SSG) as a pre-requisite to assessing its suitability for the production of value-added products and/or biofuel. The gross chemical composition of five SSG samples sourced from commercial breweries in Africa were determined, with the sum of individual components accounting for 97.8 % material on a dry weight basis (d.b.; average value). The SSG samples contained relatively high amounts of protein (>38.0 %) as compared to values quoted for brewers’ spent grains. SSG samples were found to contain considerable amounts of residual starch (>4.55 %; d.b.), which suggested that the practice for milling and mashing with unmalted sorghum, in the breweries from which samples were sourced, could be further optimised. By boiling at reduced temperature, required energy input is reduced as the latent heat of evaporation is not provided. In Chapter 3, the impact of reduced temperature boiling on the formation and stripping of key wort volatile compounds was evaluated at both industrial scale and pilot scales (10 hL). As compared to control boiling (3.5 % evaporation), the stripping efficiency of simmer boiling (0 % evaporation) was reduced for some volatiles, including: hexanal, linalool, and β-myrcene. One key lager flavour volatile, dimethyl sulphide (DMS), displayed similar patterns of stripping when comparing simmer and control boils. In Chapter 4, we report the evaluation of a novel wort boiling technology in production-scale trials at a brewery in Ghana. The ‘PDX’ wort boiler utilises direct steam injection into wort and claims improved efficiency of heat transfer and volatile stripping. The present work demonstrated that steam injection technology could provide an approximate 50 % reduction in energy input during the boil, without significant deleterious effects on final product quality. Finished beverages produced using steam injection technology were determined to be within brand specifications by a trained sensory panel. Chapters 5 and 6 report investigations aimed at reducing the energy input when mashing with unmalted sorghum and developing knowledge of how the structure and composition of different sorghum cultivars interacts with the mashing conditions employed. Designed experimentation was used to investigate the impact of mash conditions on a novel low-temperature mashing system and a high-temperature enzyme mashing system. The reduced energy, low-temperature system was comparable to the high-temperature system in terms of extract and FAN yield, when mashing with unmalted Sorghum bicolor cv. Fara Fara. Furthermore, both enzyme systems were able to produce acceptable wort using agricultural sorghum varieties, providing that the starch properties were similar to brewing cultivars in terms of their pasting characteristics and grain hardness. Poor mashing properties were associated with cultivars displaying increased physical interaction of endosperm protein with starch, resulting in reduced starch swelling during mashing.

No description available.

Membranes are a robust, reliable and economical technology. However, polymeric membranes are manufactured from polymeric and organic solvent sources derived from petrochemical sources. The high volatile organic compounds (VOC) emissions of the organic solvents and the non-recyclability of the polymers often question the membrane manufacture sustainability. The main goal of this dissertation is the preparation of polymeric membranes for liquid separation through more sustainable processes. We report here the green preparations of hollow fibers, thin-film composite and integrally skinned asymmetric membranes. An important part of the work is represented by the development of cellulose hollow fibers from ionic liquid solutions, avoiding strong alkali or harsh solvents. By tuning the manufacturing process, we prove that the membranes can be used for different applications such as oil-water separation, protein separation via ion-exchange chromatography and solvent purification via organic solvent nanofiltration. The main advantages of using cellulose to prepare hollow fiber membranes are the biodegradability of the polymer and the intrinsic chemical stability. Another significant milestone of this work is replacing volatile solvents such as hexane during the thin-film composite membrane manufacture. As green alternative solvents, we decided to use naturally extracted oleic acid and decanoic acid. Due to their low costs and volatility, they represent a valid alternative for industrial membrane preparation through the interfacial polymerization process. The membranes prepared with this process were used for solvent resistant nanofiltration. Finally, by using ionic liquids as solvents, we improved the manufacturing sustainability polytriazole asymmetric membranes synthesized in the lab.