Gelation of hydrocolloids under shear conditions results in a weak gel which is capable of sustaining elastic mechanical deformation at small strains but which flows if subjected to higher deformations (fluid gels). I have investigated the formation, production and lubrication properties of fluid gels from the gelation of agarose and -carrageenan. The formation of fluid gels in a rheometer, using well-defined, flow patterns and cooling rates have been described. Under these conditions narrow particle size distributions were achieved by inducing spinodal decomposition. The increase in viscosity due to particles formation was found to be inversely proportional to the shear rate. The power law exponents describing this relationship are provided for several hydrocolloid concentrations. The studies on the formation of fluid gels from -carrageenan, showed that it was possible to form homogeneous particle size fluid gels with mean diameter smaller than 5 μm. The fluid gels produced showed strong and highly recoverable particle bridging. A model is presented for the kinetics of aggregation of these particles, providing information on the mechanisms involved. The use of the pin stirrer heat exchanger was previously reported as the large-scale method for the production of agar fluid gels. However little work has been done in describing fluid dynamics, and specifically the shear rates. Positron Emission Particle Tracking (PEPT) was used to characterise flow phenomena occurring in a pin stirrer heat exchanger for a 1 Pa s glycerol solution and a 2% agar fluid gel. Internal recirculation paths and axial-occupancy show a compartmental behaviour, with the tracer selectively occupying specific areas. Analysis of particle paths revealed that for a rotational speed of 900 rpm the average shear rate experienced by a particle was approximately 200 s-1. Areas of poor mixing in dead-zones were also identified. These findings can contribute to a rational design of equipment and processes for industrial scale fluid gel production. Bulk rheological properties of fluid gels are similar to emulsions used in a large number of applications in everyday food products and cosmetics (Brown, Cuttler et al., 1990; Bialek, Jones et al., 2000), in order to replace emulsions their lubrication behaviour should also be fully understood. In the proposed lubrication mechanism the agarose fluid gel micro particles under specific conditions of entrainment velocity U, normal load W and elasticity E, interact with the lubricating surfaces, resulting in a localised increase in friction. A wide range of agarose concentration was studied (1% to 4%) resulting in fluid gel particles having different values of elasticity E, ranging from 5 kPa to 140 kPa, which were shown to alter their tribological behaviour, modifying the critical velocity required to induce entrainment of the particles, Uentr. For an identical particle’s elasticity, the critical velocity was found to decrease by 50% when the normal load was increased by 30%, while the opposite trend was observed when the normal load maintained constant. Fluid gel systems of the same elasticity E but of different particles sizes were also investigated. The maximum friction measured upon entrainment of the particles decreased from 0.3 to 0.2 when the average Sauter mean diameter of the particles passed from 102 m to 83 m.

In this study, three different methods have been used to investigate the bacterial interaction with the substratum, i.e. atomic force microscopy (AFM), spinning disc and micromanipulation. Pseudomonas fluorescens NCIMB 9046 was chosen as a model microorganism to study the cell-substrate adhesion. By having three different colloidal particles: stainless steel (Grade 304), glass and cellulose, the force measurements were performed in growth medium and ambient air using AFM. The results demonstrated that the adhesive forces were influenced by the surface hydrophobicity, electrostatic, van der Waals and steric interactions. In ambient air, the capillary force played an important role. The effect of shear forces on the bacterial adhesion was further examined. By using an apparatus of spinning disc, the cell removal was strongly influenced by the spinning time, angular velocity and surface hydrophobicity. Finally, the adhesive and cohesive strengths of biofilms were examined via a micromanipulation technique. Results indicate that with pH7 and low initial glucose concentration (0.25% (w/v)) the biofilm adhesion was the greatest among the conditions investigated. The cohesive strength of biofilm was found to depend on on the distance between the force probe and the substrate surface.

This thesis describes the research and development into a range of time-temperature integrators (TTIs) for the measurement of process values for food heat treatments. The TTIs are based on the first order thermal degradation of bacterial \(\alpha\)-amylases. Two new TTIs are described, one for mild pasteurisation treatments of a few minutes at 70°C and one for full sterilisation of >3 minutes at 121.1°C. Examples are given of how these TTIs are applied to a variety of industrial thermal processes. These include traditional methods such as canning, but also more complex systems such as tubular heat exchangers and batch vessels, together with novel systems such as ohmic heating. Some of the industrial experiments dealt with processes in which the thermal effects had not been previously quantified. For sterilisation, a highly innovative solution is required. A candidate TTI material is identified based on an amylase secreted by the hyperthermophilic microorganism Pyrococcus furiosus. This microorganism exists in extreme conditions where it metabolises in boiling volcanic pools; with elemental sulphur readily available, in water of high salinity, and in a reducing atmosphere. The amylase it secretes is naturally thermostable and withstands a full thermal sterilisation process.

Three dimensional scaffolds were created from a biodegradable polymer (polylactide) and the mineral silica utilising supercritical fluid (SCF) gas foaming. The effect of silica on the scaffold pore architecture was investigated through X-ray computed microtomography (microCT); the scaffolds were shown to be up to 60% porous with pore diameters in the range of 0.088-0.924 mm (0% silica) to 0.044 – 0.342 mm (33.3% silica), demonstrating that silica controlled both pore size and overall scaffold porosity; Silica was found to enhance connectivity of the pores and pore wall thickness and pore connectivity were found have an inverse relationship. Differential scanning calorimetry (DSC) was used to investigate the effect of silica on the Tm, Tg and crystallinity of the PLA pre and post SCF processing; increases in ΔHf (4J/g) Tg (1oC) and crystallinity (3%) showed that silica had a beneficial effect pre-SCF but post-SCF the PLA reverted to an amorphous state; An isothermal conditioning process was found to restore the previous levels of crystallinity. Mechanical strength testing of the scaffolds showed that silica incorporation increased the load tolerated at yield by up to 60N and the strength by up to 1.5 mPa. The scaffolds were immersed in simulated body fluid (SBF), where the presence of silica was found to enhance mineral deposition by up to 10%; they were also subjected to degradation experiments in physiological saline solution and enzyme buffer solution, where degradation was found to occur most rapidly in the amorphous regions of the polymer (0% and 9.1% silica). The formation of degradation products (lactic acid, isopropanol and lactate) were monitored through HPLC. In conclusion, addition of silica up to a loading of 9.1-16.7% was found to have many beneficial effects on the PLA scaffolds but no observable benefit was found with additions higher than this.

In this research work, the effect caused by electrical processing on mass transfer in food materials was studied by designing and performing experiments that allowed the visualisation of: the effect of moderate electrical fields (MEF \(\leq\)1000V cm\(^{-1}\)) on mass transfer in cellular materials; the effect of MEF on mass transfer of solutes to polymer networks; and the effect of MEF and pulsed electrical fields (PEF) on mechanical properties of polymer networks. MEF treatment was performed with continuous alternating current (50Hz frequency) at electrical fields up to 1400V m\(^{-1}\) using a jacket system processing cell to maintain constant temperatures. PEF treatment was performed with a pulse generator at Lund University, Sweden. Extraction of betanin from beetroot was monitored online and measured by spectrophotometry. Mass transfer of rhodamine6G into gel networks (alginate, albumin and gelatine) was measured by image analysis. Effective diffusion coefficients (D\(_{eff}\)) for mass transfer of betanin and rhodamine6G were estimated, assuming Fickian diffusion was valid. Mechanical properties of alginate and gellan gum treated with MEF and PEF were studied. Compression force of gel samples was measured with texture analysis. Results showed that the application of MEF and thermal treatment had an enhancing effect on the extraction of betanin from beetroot. The orientation of the beetroot slab also appeared to have an enhancing effect on extraction when the slab was placed perpendicular to the electrical field. The application of MEF had a decreasing effect on mass transfer of rhodamine6G to gel networks set with ions. Mass transfer decreased as electrical field increased. This effect was influenced by electrical conductivities of the gel and rhodamine6G solution. No significant effect of MEF was observed on gelatin or albumin. MEF and PEF had an increasing effect on compression force of polymer networks.

The flow pattern and distribution of energy dissipation rate in a batch rotor-stator mixer fitted with disintegrating head have been numerically investigated. Standard k-e turbulence model in conjunction with sliding mesh method was employed and the simulation results were verified by laser Doppler anemometry (LDA) measurements. The agreement between predicted and measured velocity profiles in the bulk and of jet emerging from stator hole was very good. Results showed that the interaction between stator and rotating blades generated periodic fluctuations of jet velocity, flowrate, torque and energy dissipation rate around the holes. The kinetic energy balance based on measured velocity distribution indicated that about 70% of energy supplied by the rotor was dissipated in close proximity to the mixing head, while the simulation predicted that about 60% of energy dissipated in the same control volume. Both simulations and measurements showed that jet velocity and total flowrate through holes were proportional to rotor speed, while the energy dissipation rate scaled with the cube of rotor speed. The effect of stator geometry on the flow pattern and energy dissipation rate was also numerically investigated using standard k-e model and sliding mesh method. The simulations showed that flow patterns in the holes were similar regardless of holes sizes and shapes, i.e. jets emerged in the proximity of the leading edge and they induced circulation flows behind them. The radial velocities of jets emerging from various stators plotted against normalized tangential coordinate were practically the same, however, jets tangential velocities were affected by hole width-to-depth ratio. Jets emerging from holes with large width to-depth ratio had negative tangential velocity component (the same as rotor rotation) while those from holes with small width-to-depth ratio had positive tangential velocity component (against rotor rotation). Jets emerging from stators with small hole spacing tended to merge and move tangentially, while those emerging from stators with large hole spacing tended to move radially as free jets. The power number correlated well with the total flowrate and the total flowrate correlated well with the total hole area. Both power number and flowrate were practically not affected by hole shape, hole spacing and stator thickness. For all stators investigated, high energy dissipation rate occurred in the regions around the leading and trailing edges due to stagnations in those regions. Stators with narrow holes generated more uniform energy dissipation rate profile around the holes than those with wide holes since the regions with high energy dissipation rate around the leading and trailing edges merged. The simulations also predicted that about 50 – 60% of total energy supplied by rotor was dissipated in the rotor swept volume regardless of stator geometries.

This work concentrates on the selection and improvement of differential equation based models of the penicillin G fermentation. Published penicillin fermentation models have been reviewed and compared with regard to their abilities to predict fermentation behaviour, genetic algorithms have been applied to the design of optimal experiments for model parameter estimation, and a new approach to assessing the theoretical identifiability of model structures has been proposed. When applied to the best penicillin fermentation model yet found, this new approach suggests that the model's parameters are uniquely identifiable. The best performing model was shown to be a morphologically structured model for which measurement data related to the various morphologically distinct regions were obtained using image analysis. This model was modified to increase its speed of execution, and extended to describe fermentations where lactose was present in the inoculum. Design criteria from the field of optimal experiment design were combined with genetic algorithms as a technique for searching through the range of possible input combinations, subject to constraints on the fermenter operation, to develop experimental feed profiles. The theoretical identifiability of the fermentation model has been assessed for the first time, using a novel approach to identifiability testing which uses a symbolic mathematics package, along with subsequent post-processing, to determine almost at a glance whether or not a fermentation model should be uniquely identifiable.

In order to mitigate the effects of climate change and reduce dependence on fossil fuels, carbon-neutral methods of electricity generation are required. Solid oxide fuel cells (SOFCs) have the potential to operate at high efficiencies, while liquid hydrocarbon fuels require little or no new infrastructure and can be manufactured sustainably. Using hydrocarbons in SOFCs introduces the problem of carbon deposition, which can be reduced or eliminated by judicious choice of the SOFC materials, the operating conditions or the fuel itself. The aim of this project was to investigate the relationships between fuel composition and SOFC performance, and thus to formulate fuels which would perform well independent of catalyst or operating conditions. Three principal hypotheses were studied. Any SOFC fuel has to be oxidised, and for hydrocarbons both carbon-oxygen and hydrogen-oxygen bonds have to be formed. Oxygenated fuels contain these bonds already (for example, alcohols and carboxylic acids), and so may react more easily. Higher hydrocarbons are known to deposit carbon readily, which may be due to a tendency to decompose through the breaking of a C-C bond. Removing C-C bonds from a molecule (for example, ethers and amides) may reduce this tendency. Fuels are typically diluted with water, which improves reforming but reduces the energy density. If an oxidising agent could also act as a fuel, then overall efficiency would improve. Various fuels, with carbon content ranging from one to four atoms per molecule, were used in microtubular SOFCs. To investigate the effect of oxygenation level, alcohols and and carboxylic acids were compared. The equivalent ethers, esters and amides were also tested to eliminate carbon-carbon bonding. Some fuels were then mixed with methanoic acid to improve energy density. Exhaust gases were analysed with mass spectrometry, electrical performance with a datalogging potentiostat and carbon deposition rates with temperature-programmed oxidation. It was found that oxygenating a fuel improves reforming and reduces the rate of carbon deposition through a favourable route to CO/CO2. Eliminating carbon-carbon bonds from a molecule also reduces carbon deposition. The principal advantage of blending with methanoic acid was the ability to formulate a single phase fuel with molecules previously immiscible with water.

Expanded Bed Adsorption (EBA) is a form of liquid fluidized bed adsorption chromatography employing dense chromatographic media of defined size distribution. EBA's main advantage stems from its ability to perform chromatographic separations with crude feedstocks, thereby combining three separate tasks - clarification, concentration and initial capture/purification - in one single unit operation. Still, understanding of support particle movement (solid phase dispersion) is limited, impairing the process' robustness. In this work, the technique of Positron Emission Particle Tracking (PEPT) was employed extensively to study solid phase motion and dispersion in expanded beds of commercial media. In addition to providing evidence of classification and non-uniform bed expansion in all fluidised beds under study, PEPT was used to determine kinetics of bed stabilisation and identify changes in tracer position and speed along the length of the bed in response to variations in flow rate, degree of column misalignment, and means of fluid distribution. Furthermore, adsorbent particle motion was investigated under 'real process' conditions, i.e. during the application of a porcine serum feedstock.

Chemical and physical processing in the small intestine is an important step for food digestion and absorption. Having reviewed the literature, a relevant model has been developed which enabled investigation into the fluid flow, mixing mechanisms and delivery of nutrients to the wall of the model small intestine. Designing, developing and using the Small Intestinal Model (SIM), a physical model of a section of the small intestine, mimicking the physiological contractions, allowed mass transfer to be measured using different process conditions and ingredients. Experiments were carried out using the SIM to study mass transfer, starch digestion and flow visualisation. While simulating the small intestinal flow profile, experiments have shown that the functional ingredient guar gum reduces the mass transfer coefficient of the model nutrient riboflavin. This together with computational modelling suggests an explanation for the observed functionality of guar gum to reduce the peak increase in blood glucose levels after ingestion of test meals. Industrial implications are to give a scientific and engineered design methodology for novel food formulations by understanding the food product behaviour in the SIM. Optimisation of formulation candidates going to the human trial stage and improvement of speed to market of new product introductions is intended.