There is an increasing demand from the pharmaceutical and food industries for new probiotic products. Some yeast strains offer probiotic benefits, but it has not been possible to formulate them successfully into a tablet dosage form. Direct compression is regarded as the best technique for producing tablets containing dried yeast, however, the main challenge of tabletting a powder mixture containing yeast granules is the mechanical sensitivity of the cells. The objective of this work was to develop a rigid yeast tablet containing adequate numbers of viable yeast cells by optimizing the formulation to allow a relatively low compaction force to be used. In addition the mechanical properties of primary particles and granules were determined as an attempt to predict the compaction behaviour during tabletting. A tablet formulation was developed which exhibited tablets of an acceptable tensile strength. These tablets were further tested for friability, dissolution and storage stability to ensure it is fit for consumer use.

This work presents a novel method of Sn-infiltration on SOFC anodes for SOFC operation in biogas dry reforming. Using commercially available NiYSZ-based anode supported half cells with hand-painted LSM/YSZ cathode layers, Sn-infiltrated NiYSZ SOFCs containing different amounts of Sn were manufactured. These SOFCs were tested for their electrochemical performance and quantity of deposited carbon during operation on simulated biogas of 1:2 volume ratio of CO2:CH4 without humidification but with 25% Helium added to the feed stream to enable measurements of the fuel cell outlet gas composition using a quadrupole mass spectrometer. Most of the SOFCs were tested in biogas for 1 day (22 hours), but several cells were tested for 6 days (150 hours) to evaluate performance degradation. The electrochemical performance tests at 750 oC showed that with H2 as fuel the non-infiltrated NiYSZ SOFCs were able to reliably generate a moderate level of current of 350 mA cm-2 at 0.7 V; however when simulated biogas was introduced, current dropped significantly to 90-200 mA cm-2. Contrary to non-infiltrated cells, a series of Sn-infiltrated cells under the same operating conditions performed equally well both on H2 and biogas producing 310 to 420 mA cm-2 at 0.7 V. Several cells showed stable electrochemical performance over 150 hours of operation both on H2 and biogas. Using Temperature Programmed Oxidation (TPO), both Sn-infiltrated and non-infiltrated SOFCs showed low quantities of carbon formed during 22 hours operation on biogas. Visual observation and SEM images of the anode surface after 150 hours operation on biogas showed no sign of deposited carbon. The conclusion is that Sn-infiltrated NiYSZ-based SOFC can be operated on simulated biogas with significantly higher electrochemical performance and low carbon deposition, given the anode is adequately modified.

This thesis took a unique multidisciplinary approach, combining understanding of food engineering, sensory science, nutrition and psychology, to investigate how emulsion-based food products can be made more satiating whilst maintaining or improving the products sensory and hedonic qualities. To achieve this, model oil-in-water emulsion systems were designed. Oil droplet size (0.1 µm – 50µm) was the main microstructural variable investigated. The influence of oil droplet size upon viscosity, friction, sensory perception, hedonics and expected and actual food intake behaviour was investigated. The main finding of the work highlighted oil droplet size significantly affects hedonics, expected and actual food intake behaviour and the perception of numerous sensory attributes. It was shown Creaminess was a strong hedonic indicator, but interestingly it also showed to significantly induce greater expectations of satiety and satiation. Structurally, Creaminess significantly increased with decreasing oil droplet size. Through a preload study, expectations were shown to be reflected in actual food intake behaviour, with smaller droplets resulting in a significant 12% reduction of food intake. Sensory results, indicated that the mechanism in which oil droplet size modified Creaminess was through altered texture and mouthfeel. Instrumental characterisation of the emulsions highlighted that this was a result of a combined influence of viscosity and droplet behaviour during oral processing, the sensory interpretation of these two physical variables being Thickness and Smoothness, reflecting Kokini’s Creaminess predication equation. Throughout this thesis the potential of emulsion structure on synergistically increasing both the satiety and hedonics of emulsion based foods was realised.

Efficacy of subcritical water in the recovery of the polyphenolic compounds from the apple pomace using a batch reactor system at 100-bar over a temperature range of 100-200oC for a residence time of 10–30 minutes was investigated. Organic solvent extractions using acetone and ethanol were carried out to serve as a baseline for comparison with the subcritical water extraction. Subcritical water was efficient in solubilising the apple pomace, and extracting polyphenolics with high antioxidant activity. Maximum solubilisation of the apple pomace was achieved at 145oC for 30 minutes and total phenolic content and antioxidant activity at 200oC. Solubilisation, ORAC activity and total phenolic content of subcritical water extract were 28.20g/100g DW, 99285μmol TE/g DW and 49.86mg/g GAE DW of apple pomace respectively, compared to 19.20g/100g DW, 6260.27 μmol TE/g DW and 21.70mg/g GAE DW of acetone extracts of apple pomace respectively. Protocatechuic aldehyde was identified for the first time only in the subcritical water extract and to date has not been identified in solvent extracts of cider apple pomace. Encapsulation of polyphenolic s of subcritical water extract using spray drying was explored. Particles/powders formed were derived from the naturally occurring carbohydrate polymers co-extracted with polyphenols. Addition of HPβ-Cyclodextrins (SWE+ HPβ-CD) to the directly encapsulated powder (SWE) significantly reduced hygroscopicity and improved antioxidant activity.

This research shows, for the first time, the freeze dried low acyl (LA) gellan gum, high acyl (HA) and HA:LA mixture gel structures and their properties upon rehydration. The water interaction with the gel structure is affected by the presence of acyl groups along the HA gellan gum polymer chain. The rehydration rate was shown to be lower for HA gellan gum and was not dependent on the polymer concentration. In the second instance, the effect of the gel pH on the freeze- and oven-dried structure is studied as well as the water re-absorption extent and rate. In this part, two drying methods, freeze- and oven-drying, were performed. Finally, a comparison of the three drying processes (freeze-, oven- and supercritical-fluid drying) is reported, proposing the effect on the molecular structure by investigation of the disordered chain domains of the gel network. As supercritical-fluid drying requires a pre-treatment in alcohol, its effect on the gellan gum network was investigated. It is shown how alcohols change the gellan gum configuration, leading to a considerable variation in gel texture. A novel supercritical-fluid batch rig is also proposed, characterised by high process flexibility and reduced set-up and energetic costs, particularly suitable for small/laboratory-scale use.

Many biological and non-biological materials in the form of microscopic particles (or microparticles) are used to produce functional products for a wide range of industrial sectors including pharmaceutical and medical, chemical, agrochemical, food and feed, personal and household care. Understanding their mechanical properties is essential for predicting their behaviour in manufacturing and processing, and for maximising their performance in end-use applications. However, it had not been possible to determine the mechanical properties of single microparticles until the author, as the main contributor, developed a novel micromanipulation technique at the University of Birmingham. The technique is capable of determining the mechanical properties of both biological and non-biological particles as small as 400 nm in diameter, and can be used for obtaining force-displacement data of single microparticles at large deformations, including those corresponding to rupture. The technique was enhanced by mathematical modelling and finite element analysis in order to allow intrinsic material properties to be determined, for example, the particle (or particle wall) elastic modulus, viscoelastic and plastic properties, and stress/strain at rupture. For biological materials, applications of this technique include understanding mechanical damage to animal cells in suspension cultures, yeast and bacterial disruption in downstream processing equipment, biomechanics of chondrocytes and chondrons for tissue engineering, and adhesion and cohesion of biofilms and food fouling deposits. For non-biological materials, applications include understanding and controlling particle breakage in processing equipment, and the formulation of microcapsules with optimum mechanical strength to achieve controlled release and targeted delivery of functional active ingredients. The research on micromanipulation has been sponsored by BBSRC, EPSRC, DEFRA, DTI, EU, the Royal Society K C Wong Fellowships and 19 national and international companies, and has resulted in more than one hundred academic publications. The knowledge generated has also assisted these companies to commercialise particulate functional products.

Significant growth is predicted for the bi-axially oriented polyethylene terephthalate films market, in part due to increased number of applications. Besides reduced manufacturing costs and improved material properties Direct Extrusion Addition technology offers faster new product development. Critical to success in retrofitting the technology onto existing film lines is achieving the differing dispersion requirements of flame retardant, opaque and handleable films within the constraints of the film line operating window and conventional equipment. The optimum conditions for process parameters, the role of material properties and screw design required in delivering the desired level of dispersion were identified experimentally. Fundamental understanding of average shear rate/stress coupled with characterisation of mixing via film surface analysis and/or cross-sectional analysis of pellets (shown to adequately describe the filler dispersion in films) yielded promising relationships between the total strain and the degree of dispersion achieved. The results highlighted the importance of screw speed and the minimal impact of the screw configuration. A compromise between mechanically induced chain scission led viscosity reduction and high shear required for mixing was identified. Through the development/understanding of the fundamental principles and processing requirements for good dispersion, the basis for a design guide has been developed for the technology.

Vapour – liquid equilibria were measured for the acetic acid + water and the propanoic acid + water systems, in the temperature range of 412.6 to 483.2 K and pressures of 1.87 to 19.38 bar, over the entire range of concentrations. An experimental apparatus based on the static-analytical method with sampling of both phases was used with quantitative analysis by GC. A new experimental technique comprising positron emission particle tracking (PEPT) was developed and applied for the determination phase compositions and molar volumes for the acetic acid + water system at 412.6 K. The Peng-Robinson (PR), the Cubic Plus Association (CPA), the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) and the PC-polar-SAFT (PCP-SAFT) equations modelled the data. The 1A and 2B association schemes for propanoic acid and the 2B, 3B and 4C for water, were evaluated. In CPA, the ECR and CR1 combining rules were also tested. A single binary interaction parameter was used in all models. PCP-SAFT presented higher predictive and correlative capabilities when the organic acid was modelled as 1A and water as 2B. The best association combination among CPA and PC-SAFT was 2B and 4C for the acid and water, respectively. CR1 accounted for lower errors in predictive mode while ECR in correlative mode. CPA performance was intermediate between the PC-SAFT and PCP-SAFT models and the PR equation. PR predictions were rather poor but correlations were better than those of CPA, at the expense of a larger binary interaction parameter.

Thermal treatment is the most common method used by industry to ensure food is safe for consumption and to increase storage life. To ensure safety, food is often over processed, which can significantly affect its nutritional value as well as taste and flavour attributes. In this study a candidate sterilisation time-temperature integrator (TTI) from the hyperthermophilic Pyrococcus furiosus α-amylase is investigated. Reliability and accuracy of the TTIs was determined by exposure to various isothermal and non-isothermal industrially relevant temperature profiles. The integrated temperature history obtained by the TTIs correlated generally well with the data obtained from thermocouples installed, although the error increased with hold time of heat treatment. The work showed that the TTIs can be used reliably over a range (3-25 minutes at 121°C) which is relevant for conditions of thermal sterilisation. This was measured by developing a new assay technique for assaying the activity of hyperthermophilic α-amylase within the food industry. The assay was calibrated against more laboratory relevant assays and computational models. The kinetics and mechanism of thermal denaturation of Pyrococcus furiosus α-amylase was determined through FT-IR, DSC and CD techniques. It was found that through thermal denaturation after the melting temperature (Tm), the enzyme unfolded by first order kinetics from a α-helical structure, through α-sheet structure to aggregation of the enzyme.

Vertically stirred media mills represent an important tool for the comminution of a range of industrial minerals. In this work, calcium carbonate is ground to size ranges below 2 μm in an Imerys stirred media mill. The role of grinding media on the efficiency is considered, and with the use of a novel, rod shaped grinding media, significant energy savings in ultrafine wet grinding are seen. This is proven to be an effect attributable to the shape of the grinding media, rather than the density of the grinding media. After a comprehensive efficiency analysis of the performance of a range of spherical and rod shaped media, further investigations are made through analysis of flow patterns within the mill using Positron Emission Particle Tracking (PEPT). Data collected from PEPT has given new insights into the distribution of material and kinetic energy within the mill, as well as an understanding of the effect of media density and motor speed in relation to the efficiency of the grinding. Furthermore, investigations are made into dry grinding of talc using the stirred media mill, which is subsequently soaked in water to give a low energy route to high surface area of the mineral.