Revision of a part of the author's thesis with title: Uttara Bhāratīya vastra. / Includes bibliographical references (p. [59]-62).

Thèse--Univ. de Paris. / "Documents annexes": p. 163-166. "Bibliographie": p. [7]-10.

Thèse--Universit́e de Nancy. / "Bibliographie": p. 167-168.

Proefschrift--Rotterdam, 1938. / Includes bibliographical references.

Dark chocolate as the main subject matter in this study was investigated for physical changes when formulated with two different lipids based ingredients impacting on the chocolate flow properties. The first ingredient was limonene, known to reduce viscosity when substituting a small fraction of the cocoa butter and to affect cocoa butter crystal morphology, but without knowledge of the impact on bloom formation. The second lipid ingredient was a polar lipid extract from green leaf tissue hypothesised to show functionality as a flow aid, potentially enabling the replacement of currently applied commercial surfactants in chocolate. The driver for this part of the PhD study was to uncover alternatives for the commercial surfactant polyglycerol polyricinoleate (PGPR) which has a negative consumer image. This study was also carried out to devise an opportunity for functionalisation of green tissue waste, although in this first investigation, fresh spinach was used as the raw tissue material. As DGDG was claimed to be the polar lipid compound that caused the low viscosity reduction of dark chocolate by oat lipids, DGDG as well as MGDG are also available abundantly in spinach. The limonene work was using the techniques of whiteness index (WI) to detect bloom, X-ray diffraction (XRD) for crystal identification and differential scanning calorimetry (DSC) for the melting behaviour. Limonene significantly influenced the cocoa butter crystal transformation rate in chocolate which further promoted the development of clearly visible bloom. Nevertheless, limonene may still commercially can be applied in chocolate filling or white chocolate bars where bloom formation is not visible. Polar green leaf tissue lipids were extracted from both spinach leaf and spinach chloroplast due to their difference in composition. Based on compositional analysis of the lipids and their fatty acids by thin layer chromatography (TLC) and gas chromatography (GC), respectively, it was confirmed that leaf contained higher proportion of phospholipids compared to chloroplast, which was highly concentrated with glycolipids. The surface active nature of both lipid extracts was confirmed by interfacial tension measurements at the oil/water interface. Leaf and chloroplast lipid showed a comparable surface activity and demonstrated to be more surface active than lecithin and PGPR. Before applying as flow aid into a complex chocolate formulation, sugar/oil suspensions with added surfactant were rheologically analysed. The performance of the two green tissue extracts was compared to the commercially applied lecithin and PGPR in a concentration range of 0.1 % to 0.7 % based on total suspension containing between 40 and 50 % sugar by weight. Both spinach leaf and chloroplast lipids showed a comparable result in influencing the rheological properties of chocolate model. Therefore, due to the higher lipid recovery from leaf compared to chloroplast as the basic of parent leaf, application in chocolate to verify the results obtained for the model system was executed only for leaf lipid extract. Based on the model suspension results addition at 0.3 and 0.6% on chocolate by weight was considered. Spinach leaf lipid decreased the viscosity of chocolate to value lower than lecithin and PGPR added at the both levels. Yield value measured at 5 s-1 was also reduced; at both levels of addition providing an advantage over lecithin which was shown and is known to increase yield stress at higher level of addition. On the other hand, the yield (5 s-1) lowering capacity was less pronounced than PGPR whereas it was found to be effective based on the model chocolate system. The present results show promise for green leaf tissue lipid to be applied as surfactant in chocolate or fat based food suspension although further research is required to develop the full potential of this natural surfactant system.

The high potential of health beneficial polyphenols and antioxidants in cocoa beans has been a major topic for research in recent years. The large-scale application of cocoa beans for health beneficial compounds is relatively unexplored and it needs to be widely utilized by pharmaceutical and nutraceutical industries. Processing methods such as fermentation and drying are major deterrents for recovering high polyphenols in cocoa beans. Hence, it was the intention of this work to introduce the application of hot water blanching pre-treatment and various drying methods for producing polyphenols rich cocoa beans by using unfermented beans. The studies incorporated the application of various drying methods such as oven, adsorption, vacuum, freeze and sun drying methods on cocoa beans. The studies compared the ability of these drying methods to preserve the bioactive capacities namely, total polyphenolic contents and antioxidants activity after hot water blanching. The potential of adsorption, vacuum and freeze drying methods for recovering high polyphenols content are useful in comparing it with the conventional cocoa drying methods such as oven and sun drying methods. For the studies on oven drying of cocoa beans, the drying parameters (T= 60°C, 70°C and 80°C) used were similar to the conventional hot air drying parameters used in industries. The total polyphenolic contents of fermented cocoa beans dried at 70°C was found to be the highest. The polyphenols degradation kinetics for oven drying method of cocoa beans was determined using first-order reaction kinetics model based on various drying temperatures and durations of drying. The studies on drying kinetics of fresh cocoa beans dried using oven, vacuum, adsorption and sun drying methods were successfully analysed. It was found that adsorption drying and vacuum drying methods dried cocoa beans faster than oven and sun drying methods. Two respective falling rate periods were recorded by adsorption and vacuum drying. The effective diffusivities were determined and were found to be in accordance to that of published literatures. Hot water blanching pre-treatment were performed for fresh and fermented cocoa beans (whole beans and half cut). Blanching pre-treatment method was found to show significantly higher total polyphenolic contents when compared with unblanched cocoa samples. The optimal blanching parameter (90°C for 5 min) obtained for fresh beans were subsequently used for experiments involving fresh cocoa beans. The total polyphenolic contents and antioxidant activity of blanched and unblanched cocoa beans were analysed. Results showed that both adsorption and vacuum drying methods showed high recovery of polyphenolic compounds and antioxidants on comparison with freeze dried cocoa samples, which was used as a benchmark in quality analysis of food products. High polyphenols contents were achieved after the blanching and drying treatments and were noted to be significantly higher on comparison with published literatures. Sensory analysis of both blanched and unblanched cocoa beans were analysed after drying using various drying methods. The results for unfermented cocoa beans showed high astringency flavour attributes which further confirmed the high contents of polyphenols in cocoa beans. The cocoa and acidic flavour attributes were recorded to be less owing to the unfermented nature of cocoa beans. The results obtained provides a gateway towards the use of advanced drying technology in cocoa industry. The potential of blanching pre-treatment to mediate high recovery of cocoa polyphenols after drying has been proven through this work. The processing methods used in the current study can be implemented in on-farm cocoa processing, making it a more sustainable farming option.

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The electrical properties of sulfonated polyaniline (SPAN) and polyaniline (PANI) grown on both conventional (100) and high Miller index GaAs surfaces are investigated. These devices were electrically characterized using Current-Voltage (I-V), Capacitance-Voltage (C-V), Capacitance-Frequency (C-F), Capacitance-Conductance-Frequency (C-G-F), Deep Level Transient Spectroscopy (DLTS), and Laplace DLTS measurements in the temperature range 20 – 440 K. Electrically active defects are generated at/near the interface and away from the interface with energy levels deep in the bandgap of the materials. These defects considerably affect the electrical and optical properties of the devices. This thesis reports the effect of n-type GaAs substrate orientation, namely (100), (311)A and (311)B, on the electrical properties of sulfonated polyaniline (SPAN)/GaAs heterojunction devices. It was found that the interface state density (Dit) of SPAN/(311)B GaAs samples is lower than that of (100) and (311)A GaAs devices. This behaviour is attributed to the effect of crystallographic orientation of the substrates, and was confirmed by DLTS results as well. In addition, the inhomogeneity of the interface between various GaAs substrates and SPAN is investigated in terms of barrier height and ideality factor by performing I–V measurements at different temperatures (20–420 K). The I–V results indicate that the value of the rectification ratio (IF/IR) at 0.5 V is higher for SPAN/(311)B GaAs samples than for SPAN/(100) GaAs and SPAN/(311)A GaAs samples. Moreover, the barrier height decreases and the ideality factor increases with decreasing temperature for all three heterostructure devices. This thesis also reports an extensive study of the electrical properties of PANI/GaAs (organic-inorganic) hybrid heterojunctions. Polyaniline (PANI) thin films were deposited by a very simple technique on (100), (311)A and (311)B ntype Gallium Arsenide (GaAs) substrates to fabricate hybrid devices with excellent electrical properties. The DLTS and Laplace DLTS measurements illustrated that the number of defects at/very close to the interface region in PANI/(311)A GaAs samples is lower than those of PANI/(100) GaAs and PANI/(311)B GaAs samples. Moreover, the analysis of I–V characteristics based on the thermionic emission mechanism has shown a decrease of the barrier height and an increase of the ideality factor at lower temperatures for all the three hybrid devices. The interface states were analysed by series resistance obtained using the C–G–V methods. The interface state density (Dit) of PANI/(100) GaAs devices is approximately one and two order of magnitude higher than that of PANI/(311)B GaAs and PANI/(311)A GaAs devices, respectively. Additionally, the devices show excellent air stability, with rectification ratio values almost unaltered after two years of storage under ambient conditions, making the polyaniline an interesting conductor polymer for future devices applications.

Non-food lignocellulosic biomass is the most abundantly available raw material. Utilising it for biorefinery purposes not only circumnavigates the food vs fuel debate, but is also important for a complete move to a fossil fuel free society. Some of the major challenges in using lignocellulosic feedstock includes its recalcitrance, potential shortage for year-round mono feedstock supply and economic viability with current technology. The first part of this thesis explores the potential of overcoming recalcitrance of wheat straw by exploiting new wheat back cross (BC1) plants, which were developed at Nottingham, using introgression of genes from wild relatives, with the aim to improve wheat genetic variation. The straw from a subset of 128 BC1 were screened for sugar content and saccharification efficiency. Plants showed wide compositional and structural differences, reflecting a high degree of genetic diversity. The digestibility of the stem tissue was assessed following acid hydrothermal pre-treatment and a significant variation was detected. This demonstrated that this approach to wheat breeding was successful in introducing a wide range of phenotypic, compositional and structural changes and digestibility into the wheat straw. The second part of the thesis aimed to address the potential bottle neck in mono-feedstock availability in a biorefinery, as most lignocellulosic feedstocks are likely to be seasonal. One way to overcome this may be by utilising a mixed feedstock to maintain a year-round supply. This study reports the impact of mixing three of the UK’s most important feedstocks- wheat straw, willow and Miscanthus on two major performance indicators - sugar yield and fermentation inhibitor production. A hot water pre-treatment regime of 200°C for 5 minutes was applied to each feedstock individually and to 1:1 (w/w) mixes and the predicted sugar yield in the mixes was compared to the observed values. All the mixes resulted in improved sugar yields with willow + Miscanthus and wheat + willow showing a statistically significant improvement over predicted values. Inhibitor production during the pre-treatment and its impact on yeast metabolism and growth were also compared and no adverse impacts of mixing observed. The use of mixed feedstocks in a hot water based commercial production of biofuels is unlikely to have any adverse effects on productivity and may indeed prove beneficial. The final part of the thesis, explores the potential of combining extraction of a high value product (anthocyanin) from black rice - Chakhao poireiton straw, followed by use of the residual straw for saccharification for an economical biorefinery.
The anthocyanin content of black rice straw, as determined by standard methanol extraction, was 62.8±4.2 mg/100g. Aqueous microwave treatment at 90°C for 5 minutes extracted 85.8% of this anthocyanin and importantly the extract then displayed higher antioxidant capacity compared to methanol extracts. Extracts showed negligible cytotoxicity, or induction of apoptosis, on Jurkat cell lines even at high concentrations (200-800μg/ml). The straw residue after anthocyanin extraction showed a glucose digestibility of 49.67±1.4% after a subsequent pre-treatment at 200 °C for 5 minutes.
This study demonstrates the potential to develop a combined biorefinery process for anthocyanin and second-generation sugars using black rice straw as the feedstock.

This thesis presents two models for optimizing and guiding the micro injection moulding process. The models are generated by the use of a mathematical procedure, an understanding of the process, and empirical data obtained from several sets of experiments. Micro injection moulding is a well-known process that is heavily used in the mass production of micro polymer parts. It is a very reliable process and apart from the initial investment required for manufacturing a mould, the process is very low cost. Furthermore, polymer developments have led to the process being suitable for the production of micro parts in equipment used in several industries such as medical, automotive, aerospace and sensing. Due to these important industrial applications, several quality criteria have been the subject of research in recent years. One of the main challenges in micro moulding is the modelling of the process in terms of polymer flow and accuracy. This is because current available models use PVT data (pressure, volume, temperature) that is used for modelling of conventional injection moulding. Furthermore, these models ignore several factors in micro moulding such as the high shear rates and 3D flow of the polymer melt. Moreover, modelling of the mechanical properties of the micro parts based on mathematical systems used for macro parts leads to large errors. This study proposes a new method for modelling the effect of process parameters on the dimensional accuracy and UTS (Ultimate tensile strength) of micro walls. This results in reduction of risk and cost, and optimization of the process. The “accuracy model” relates the dimensional error to four process parameters (polymer melt and mould temperature, and injection velocity and pressure), polymer characteristics (density, specific heat capacity and thermal conductivity) and a characteristic of the machine (plunger diameter). The “mechanical model” relates the part’s UTS to the same parameters as in the accuracy model. In order to develop the “accuracy model” an understanding of the effect of process parameters on dimensional accuracy and the polymers needs to be obtained. Several sets of experiments were conducted to investigate and establish this effect. Two polymers, Polyoxymethylene (POM) and Polypropylene (PP), were used to conduct the study. The results showed that the polymer melt temperature had the highest effect, followed by injection pressure, injection velocity and mould temperature. Amongst these, injection velocity had an adverse effect on dimensional accuracy. Further analysis was done to investigate whether the effect was consistent for several sets of the parameters. Results of the experiments showed that while the effect was not linear, the trends obtained earlier were correct. The same procedure was applied to investigate the effect of process parameters on the UTS of the micro walls. Polymer melt temperature had the highest level of influence, followed by injection velocity, injection pressure and mould temperature. Increase in all parameters resulted in reduction of the UTS, except for the mould temperature. Next, the two models were developed through a method called dimensional analysis. Several dimensionless expressions were developed to form a general relationship between the parameters and the quality criteria. Then, the obtained results and data were used to find the constants and the specific form of the functions. The overall models were validated by a fresh set of selected experiments using an original brass insert. The achieved trends and models were validated experimentally, using a different mould insert with a micro channel with a different dimension. While the values for the dimensional error and UTS were different, the trends obtained before were correct for the new insert. The same trend was observed with the models. Again, predictions for PP parts had better agreement with experimental data compared to those of POM. In addition, the amount of error for the steel insert was higher, due to different thermal conductivity of the insert material and surface roughness of the micro channels.