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The relative organoleptic stability of the British fresh pork sausage among meat products has been shown in this study to be due more to a biochemical effect of SO2 than to its antimicrobial activity (except for an inhibition of coliforms). Sulphiting doubled the storage life of film-wrapped sausages to four days at 20-22°C, prevented the formation of a strong cheese-like aroma, reduced the degree of colour change observed, prevented the accumulation of valeric acid, reduced the amounts of lactic acid, and a second unidentified acid, formed by ca. 50%, caused the accumulation, by preventing the metabolism, of C12-C20 free fatty acids (but did not prevent the hydrolysis of glycerides), and limited the concomitant change in pH to 0.5 units. The microbial association which developed under these conditions did not differ significantly in composition or size from that detected in unsulphited sausages, a finding which agreed with the results of Abbiss (1978) and Brown (1977). Organoleptic change in the sulphited product, from acceptable to unacceptable, occurred when the microbial association at its surface exceeded 108 c.f.u./g. The climax at ca. 108.5 c.f.u./g. quickly followed, and the subsequent wave of post climax cell lysis was thought to contribute significantly to the quality changes perceived. It was found that both the growth of the flora, and the pH change, were affected by glucose when SO2 was present. A supply of glucose was envisaged as necessary to sustain the flora and maintain organoleptic stability, but a limitation to its availability was necessary to prevent too rapid microbial growth, an earlier climax, and, as a result, a shorter shelf-life. Of the sources of glucose studied, sausage rusk was found best to satisfy these requirements cheaply. In addition it contributed a "baked cereal" component to the aroma of the sausage, and this was regarded as a characteristic and desirable feature.

The concentrations of several organic acids have been estimated quantitatively in commercial and experimental worts and beers. All of the worts contained acetate, pyruvate, lactate, pyroglutamate, malate and citrate. During fermentations, yeast excreted pyruvate, lactate, succinate, usually 2-oxoglutarate and malate, and sometimes 2-hydroxyglutarate and citrate. The concentration of pyroglutamate in wort was unaffected during fermentations with brewing strains of yeast, and acetate concentrations oscillated during fermentation. Pyruvate was re-assimilated by yeast towards the end of some fermentations. The total concentration of organic acids in beer was higher than that in the wort from which it was fermented. The strain of yeast, wort compositioa, wort pH value and availability of oxygen to the yeast and wort prior to fermentation all affected the organic acid concentrations in beers, and the reasons for these effects are discussed. Pyruvate, 2-oxoglutarate and 2-ydroxyglutarate concentrations were found to be dependent on the extent of yeast growth, whereas malate, lactate and succinate were dependent on the degree of sugar utilisation during fermentation; acetate excretion demonstrated a negative correlation with yeast growth. It is concluded that organic acids may be excreted by yeast during fermentation (a), to control the intracellular pH value, (b) as a means of removing from the cell excess carbon resulting from amino acid metabolism, and (c), to control the intracellular balance. Exeretion of organic acids into the fermenting wort, and assimilation of basic amino acids from it were found to be significant in causing the pH value to decrease during fermentations, and solution of carbon dioxide and absorption of primary phosphates contributed to a small extent. The initial buffering capacity of wort was important in determining the pH value of beer, although the buffering capacity measured in the relevant range (pH 4 to 5) changed little during fermentations, and therefore did not contribute to the observed pH fall during fermentation. It is concluded that small peptides and, to a lesser extent, citrate, are responsible for buffering worts and beers within the pH range 4 to 5, these compounds neither being assimilated nor excreted to any great extent by yeast during fermentation.

It has been demonstrated that in fresh sausage different microbial populations, dominated by either M. thermosphactum, yeasts or lactobacilli, may develop on storage in response to the storage history of the meat used in manufacture and other factors such as the level(s) of HSO3- or SO32- contained. In sausages with a typical microbial content sulphite does not affect significantly the growth of the most numerous contaminants, except during chilled storage when the growth of the Gram negative mesophiles is significantly reduced by sulphite. Experimental data suggests that sulphite reduces the growth rate, but not necessarily the growth yield of microbes. Evidence both statistical, from routine sampling, and from model experiments using sausage components, suggests that microbes principally grow in association with the meat particles, their growth rates and ability to produce metabolites capable of binding sulphite being enhanced by their proximity to meat particles. Considerable amounts of sulphite are lost irreversibly from the sausage during storage (probably by a first-order oxidative reaction). Chilled storage does not reduce the rate of sulphite loss, but it does reduce the rate of sulphite binding. Bound sulphite can be recovered experimentally, as free SO2, by an alkalisation procedure. The existence of oxygen tension gradients within a pack of sausages axe shown by the presence of oxymyoglobin at the periphery and metmyoglobin at the core. The depth of the oxygenated layer decreased during storage, although chilled storage slowed the rate of decrease. The atmospheric oxidation of sulphite which is catalysed by meat pigments (pro- or anti-oxidative) may be affected by the availability of oxygen at the various sampling sites. Sulphite may also be oxidised by the hydroperoxides produced during the similarly catalysed oxidation of unsaturated fats. Such reactions, exhibiting first order kinetics, were demonstrated in model systems by measurement of both free sulphite loss and oxygen uptake rates. In commercially produced sausages the extent of sulphite binding increases during storage. The ability of microbes isolated from sausages, to bind sulphite with their metabolic products was demonstrated using a Schiff's base reaction. Sulphite binding by the solids in sausage (separated by chilled centrifugation) could not be demonstrated consistently. Good correlation, but not equivalence, could be demonstrated between the two methods, steam distillation and electrometric assay, used for the determination of free and bound sulphite levels. The reliability of the estimate of the bound sulphite levels determined was dependent on the procedure used to alkalise the sample. A reduction in the dry weight component of the buoyant layer (obtained from sausage by chilled centrifugation) during storage was noted; its proportional composition (fibrous material v material extracted with propan-2-ol) also altered. Compositional changes, detected using t.l.c., suggested that lipolysis of triglycerides occurred during storage. The rate and extent of such changes was dependent on sampling site, the presence or absence of sulphite and storage temperature. Changes in the level of glycerol in the sausage suggested that large quantities are metabolized during storage.

Honey bees are pollinators, accounting for around 90% of commercial pollination of animal-pollinated plants and approximately 35% of global food production. Global populations of honey bees have declined significantly recently with heavy losses attributed to Colony Collapse Disorder, pesticides, parasites and pathogens. One of the factors that may be contributing to an increase in susceptibility to these stresses is the quality of food available in a hive. This thesis focuses on the interactions between honey bee nutrition, microbial communities and fitness. In Chapter 2 the nutritional composition of bee bread (pollen stored inside hives) was studied. The composition in terms of protein and reducing sugar was found to vary both spatially and temporally; lipid and starch content was found to vary temporally through the season. The spatial trends in protein content were found to be associated with changes in landscape composition, as estimated by the Countryside Survey database. The implications for these findings are that certain landscape types may produce higher quality diets for honey bees. In Chapter 3, the link between nutritional composition of bee bread and the species of plant that comprise it was investigated. Previous research indicates that pollens vary in their nutritional content and using molecular tools, we investigated the impact of complex plant communities in this system. The number of plant species in bee bread was positively correlated with increasing protein levels, and specifically certain individual plant species were found to be driving this pattern. These results indicate that a more diverse diet of plants will benefit honey bees by increasing their dietary protein intake. The conversion of pollen to bee bread requires the activity of certain microorganisms. In chapter 4, we again used molecular tools to study the microbial community found associated with bee bread. We found a community that was not significantly different between hives located in different areas, but which varied significantly in is composition through the beekeeping season. This suggests that the environment does not determine the bacterial communities in honey bee hives; rather it is being determined by seasonal changes. Finally, in chapter 5 the relationship between the nutritional composition of bee bread and the immunocompetence of larval and adult honey bees was examined. The results showed that dietary protein and carbohydrate is significantly correlated with the overall fitness of a hive in terms of expression a constituent immune response. The link between landscape composition and nutrition established in chapter 2 was used to predict honey bee nutrition across the UK, and then was used to predict immune response for all UK bees. These predictions were comparable to honey bee disease records maintained by UK government. This thesis provides a detailed examination of the effects of landscape composition on honey bee nutrition and immunity. The results presented here have implications for understanding spatial patterns in bee fitness and bee disease epidemiology.

The aim of this research is to determine if products made via the two cooking processes named are producing materials with similar properties thus resulting in a similar consumer perception or whether two fundamentally different products are being obtained. The presented work investigates the correlations between mechanical behaviour, fracture response, microstructure, acoustic emissions and sensory evaluation of a wide range of products made via the extrusion and baking processes. The internal microstructure of the products was examined with a Scanning electron Microscope (SEM). A notable difference between the distributions of the cells was observed between the two products; the wafer comprised of separate skin and core regions with variable pore sizes whereas a more uniform distribution of the pores was present in the extruded products. The mechanical behaviour of both, the extruded and baked, products was characteristic of brittle foam. The extruded products were all found to be stiffer materials in compression when compared to the baked wafers and the extruded products were found to be less anisotropic when compared to baked wafers. Analytical models were used to determine the actual mechanical properties of baked wafer and it was concluded that taking the geometry of the baked wafer into account was essential in finding accurate properties. Sensory, acoustic and mechanical testing results were successfully compared to draw links between the structure-property-texture of the different food products. X-ray Micro tomography (XRT) was used to attain a stack of image slices of the extruded tube architecture which was used to create Finite Element (FE) model of the product volume. Representative Volume Element study was conducted and the ‘crushable foam’ material model was implemented on the FE model to study the microstructure behaviour under compressive loading. The model of the complex architecture was able to predict the deformation behaviour of the extruded product. For future study, the FE models can be used to modify the microstructure to perform parametric studies to quantify the effect of individual geometric variables i.e. pore diameter, on the global response.

Initial work presented in this dissertation on extrusion supports the findings of others with regard to standard die extrusion. In addition, comparisons between ram and screw extrusion results were made and are briefly discussed. In relation to wide sheet extrusion, unusual flow instabilities in the form of central line splitting of the extrudates were observed for the first time, indicating that the chocolate was weak in tension. Solutions for eliminating for flow defects are also presented and mathematical modelling provided insight into the flow mechanism. Post extrusion mechanical characterisation of the extruded chocolate was carried out by means of bending and indentation tests and the effect of processing conditions on the flexibility and hardness of chocolate extrudate was examined. The results showed the presence of a two-stage, post extrusion rehardening process, which was consistent with earlier findings. In terms of stamping, the process itself and the effect of processing variables on the shape formability and surface gloss formation in the chocolate product were established for the first time. Optimal conditions that contributed to the formation of well-defined products with high gloss finish were identified. Product demoulding was also found to be facilitated with the use of a Teflon die. Both the wide sheet extrusion and the stamping process were simulated by numerical models using the finite element codes Forge 3® and 2® respectively. In general, good agreement was achieved between the experimental and numerical results. Moreover, a preliminary, semi-analytical model was proposed to describe the mechanism of surface gloss formation during stamping.

Globally there have been many challenges in establishing effective food safety control systems. Of particular interest to the Sultanate of Oman is the control of the safety and quality of seafood for its importance to the national economy, food security and trade. The research focused on the particular issue of food safety management systems (including the application of the Hazard Analysis Critical Control Point (HACCP)) system within the Omani seafood processors. To understand the whole context, a wider review was initially conducted which looked into the whole structure of food control in Oman including the legal documents and the administrative structures. The evidence indicates that there is no unified national food safety agency and that current laws and regulations are shared across various governmental authorities. By investigating the various challenges, weaknesses and strengths of the existing system it is noted that there are still deficiencies in comparison to international guidance. Subsequently the structure of the seafood supply chain was analysed and a survey was conducted to assess the issues pertinent to HACCP implementation in the seafood industry and the role of the regulatory authorities in governing the safety of seafood products. The survey identified more precisely the benefits and barriers of implementing the HACCP system for the HACCP processors and the non-HACCP processors, which are usually small industry. In conclusion, the research has shown the importance of adopting strategies to enhance safety and quality requirements from farm to fork covering all aspects of seafood harvesting, processing and distribution regardless of the target markets. A legal requirement to adopt HACCP systems and the application of related food safety management systems (FSMSs) and their pre-requisites programmes is recommended. It should be imposed on all seafood processors regardless of their markets to ensure conformity with national and international requirements.

The aim of the work was the optimisation of conditions for the extraction of juice from surplus bananas using pectolytic enzymes. Juice extracted in this way could be 'used to make other products, e.g. beverages, wine, vinegar. Bananas were supplied by Geest Industries Ltd., and were of known history and variety (Cavendish). The sample~ w'ere allowed to ripen under controlled conditions of temperature and relative humidity, and were enzyme-treated at the same degree of ripeness as determined by sugar content (18.0 + 0.3% w/w).