The aim of this PhD study was to investigate the utility of membrane bioreactors (MBR) for intensifying maturation processes within alcoholic beverages, particularly cider. This has been achieved by investigations into four main areas of research: 1) Selection and optimisation of the biocatalyst; 2) Selection and construction of a suitable membrane and membrane bioreactor; 3) Optimisation of the reactor configuration and operation; 4) Rapid production of two quality cider products. Two cider products were successfully produced. The first as blended to the Scrumpy Jack recipe and was made from an all bittersweet concentration fermentation. This product was very full flavoured and was believed to be an example of a flavour concentrate which could be blended with unmatured cider either in the UK or overseas to give a product with a perceived traditional English bittersweet cider flavour. The second cider was blended to the Strongbow recipe and was a general base cider taken from the full scale plant at the end of the alcoholic fermentation and matured in the membrane bioreactor, 1 hour contact time. This product was indistinguishable from the full scale factory product which is matured for an average of 30 days. These studies provide a basis for developing strategies for rapid maturation of cider using MBR. Future work for further optimisation of the MBR operation with real cider are discussed. MBR maturation remains to be compared with other rapid maturation systems for economic viability.

The objective of this work is to remove ethanol from an alcoholic drink by using the adaptable biochemistry of yeast in a Membrane Bioreactor. Two yeast types (small and normal sized <i>Saccharomyces cerevisiae</i>) stored with different carbon sources of ethanol and glucose were used to carry out aerobic batch culture stirred tank fermenter experiments, using ethanol as the sole carbon substrate, to obtain Monod kinetic parameter values for use in theoretical mathematical models, derived in this work for an ideal Membrane Bioreactor. Aerobic batch culture experiments on ethanol as the sole carbon substrate revealed that two growth phases and two or three substrate uptake phases were present within the time course of a single batch culture experiment. The formation, extrusion and re-uptake of ethyl acetate was seen to occur during the time course of the aerobic batch culture of yeast on ethanol as the sole carbon substrate. Mass transfer experiments on the Membrane Bioreactor were carried out to obtain the overall mass transfer coefficient for ethanol across the dialysis membrane from the beer stream into the yeast stream, for use in the design of an ideal Membrane Bioreactor, and the testing of an experimental bioreactor. Membrane Bioreactor experiments were carried out in order to investigate the removal of ethanol from an alcoholic liquor. These experiments revealed that the Membrane Bioreactor was initially rate controlled by the bioreaction of the yeast in the system, which then switched to mass transfer rate control about half way through the experiment. Comparison of the experimental data with the ideal theoretical model showed that a change in yeast kinetic values, during the time course of the experiment, caused the experimental data to deviate away from the theoretical model which used constant kinetic values for the entire analysis of the experimental run. Recommendations for future development work have been made.

The analysis presented in this thesis is an application of the finite element method to the determination of the temperature, moisture content and pressure distributions within a capillary porous body. Luikovs system of partial differential equations, which are based upon the thermodynamics of irreversible processes, are used to describe the heat and mass transfer phenomena. Earlier research into this field assumed that the sole method of moisture transfer was by diffusion and that the pressure gradient within the capillary porous body was negligible and did not affect the solution. In this thesis, it is demonstrated that the presence of a pressure gradient arising within the body, which causes a filtration transfer of moisture to occur, can have a significant effect upon the transient temperature and moisture content solutions. Three numerical models were developed, firstly, a fully non linear model, where all material properties are permitted to vary, and secondly, partially non linear models for homogeneous and non homogeneous problems, where some material properties are held constant and the concept of moisture potential is introduced. The computational model was applied to the specific problem of freeze drying of coffee and the numerical solutions were compared with experimental results to validate the model.

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