Campylobacter jejuni is the leading cause of bacterial foodborne poisoning in the developed world. The impact of infection is mainly economic, however the disease can lead to severe post infection complications, such as Guillain–Barré syndrome. Despite the fastidious nature of C. jejuni, it is able to survive food chain transit. One survival mechanism proposed to aid in C. jejuni food chain survival is its formation of, or incorporation into, biofilms. Biofilms are defined as a surface attached microbial population, surrounded by a self-produced extracellular matrix. Previous work has shown that biofilm formation by C. jejuni is increased in food chain relevant conditions, but C. jejuni biofilms have received little attention compared to other foodborne pathogens. The work presented here investigated how biofilms may enable C. jejuni survival within the food chain. In order to achieve this aim, investigation was carried out into three complementary areas. Initial investigations showed that supplementation of medium with chicken juice increased C. jejuni biofilm formation, due to the chicken juice conditioning the surface and allowing easier attachment of C. jejuni. In order to distinguish between the biofilm population and surface attached particulates, a novel method of staining C. jejuni biofilms, using a metabolic formazan dye, was developed and optimised. As biofilm formation by C. jejuni is relatively poorly understood, a broad investigation was performed to increase understanding of C. jejuni biofilm formation and structure. Finally, the role of extracellular DNA within the extracellular matrix was investigated. The results presented here suggest that C. jejuni is able to utilise biofilm formation as a food chain survival mechanism. However biofilm persistence can be limited by enzymatic treatment of the biofilm and thorough cleaning of surfaces, limiting the potential for surface contamination.

The tiger nut tuber of the Cyperus esculentus L. plant is an unusual storage system with similar amounts of starch and lipid. The extraction of its oil employing both mechanical pressing and aqueous enzymatic extraction (AEE) methods was investigated and an examination of the resulting products was carried out. The effects of particle size and moisture content of the tuber on the yield of tiger nut oil with pressing were initially studied. Smaller particles were found to enhance oil yields while a range of moisture content was observed to favour higher oil yields. When samples were first subjected to high pressures up to 700 MPa before pressing at 38 MPa there was no increase in the oil yields. Ground samples incubated with a mixture of α- Amylase, Alcalase, and Viscozyme (a mixture of cell wall degrading enzyme) as a pre-treatment, increased oil yield by pressing and 90% of oil was recovered as a result. When aqueous enzymatic extraction was carried out on ground samples, the use of α- Amylase, Alcalase, and Celluclast independently improved extraction oil yields compared to oil extraction without enzymes by 34.5, 23.4 and 14.7% respectively. A mixture of the three enzymes further augmented the oil yield and different operational factors were individually studied for their effects on the process. These include time, total mixed enzyme concentration, linear agitation speed, and solid-liquid ratio. The largest oil yields were obtained with a solid-liquid ratio of 1:6, mixed enzyme concentration of 1% (w/w) and 6 h incubation time although the longer time allowed for the formation of an emulsion. Using stationary samples during incubation surprisingly gave the highest oil yields, and this was observed to be as a result of gravity separation occurring during agitation. Furthermore, the use of high pressure processing up to 300 MPa as a pre-treatment enhanced oil yields but additional pressure increments had a detrimental effect. The quality of oils recovered from both mechanical and aqueous enzymatic extraction based on the percentage free fatty acid (% FFA) and peroxide values (PV) all reflected the good stabilities of the oils with the highest % FFA of 1.8 and PV of 1.7. The fatty acid profiles of all oils also remained unchanged. The level of tocopherols in oils were enhanced with both enzyme aided pressing (EAP) and high pressure processing before AEE. Analysis on the residual meals revealed DP 3 and DP 4 oligosaccharides present in EAP samples but these would require further assessment on their identity and quality.

BACKGROUD: The industrial cereal brans produced as by-products of milling have been confirmed to be rich sources of arabinoxylans (AXs). The immunomodulatory properties of the extracted AXs from cereals have been reported, which potentially lead to corresponding health benefit in immune enhancement. However, this requires a clearer understanding of the relationship between the molecular structures of AXs and their immune-modulating activities (the structure-activity relationship). It is also considered essential to gain an understanding of the mechanisms of the immune-modulating properties of AXs. AIMS & DESIGN: The aims of this study were to develop and improve the AXs extraction process from pentosan fraction of wheat flour and corn bran and to examine the molecular structures of extracted and modified AXs and investigate the molecular structure-immunomodulatory activity relationship in vitro for AXs. The effects of the different enzymatic extraction conditions (endoxylanase dosage, extraction temperature and time) on AXs extraction yield from the pentosan fraction of wheat flour were investigated by using a Box-Behnken experimental design and response surface methodology. For the AXs extraction process from corn bran, various extraction methods (alkaline, aqueous and enzyme extraction methods) were studied and compared. In addition, the treatments of three varieties of endoxylanases for AX molecular structure modification were studied. Furthermore, the extracted and modified AXs with different molecular structures were investigated with respect to their ability to modulate nitric oxide (NO) production and inducible NO synthase (iNOS) expression in vitro as an indication of their immunomodulatory potential. RESULTS: From the pentosan fraction, the maximum recovery rate of AXs reached 86% of total pentosan AXs (dry matter basis) under the optimum extraction conditions. In contrast to the AXs obtained by aqueous extraction, the molecular weight (Mw) distribution of enzymatically extracted AXs was significantly different being more concentrated in the low Mw range (1KDa to 10KDa). The degree of branching (A/X ratio) increased from 0.48 to 0.83 as the concentration of enzyme increased. From the corn bran, using alkaline treatment, the recovery rate of AX was up to 80% (dry matter basis) of total corn bran AX and the Mw distribution of extracted AXs was in the high Mw range (100KDa to 794KDa). Following enzymatic modification, more than 30% of AXs extracted were reduced to the lower Mw range (0.1KDa to 10KDa). In vitro studies showed that the extracted and modified AXs from these two cereal sources significantly elevated the level of NO synthesis and iNOS expression by U937 cells (p<0.05), but modified AXs with higher portion of low Mw showed stronger activity than extracted AXs with higher portion of high Mw (p<0.05). It was also observed that the stimulatory effect of AXs on NO production by U937 cells was associated with their concentrations and sources. In addition, the investigation on the immune-modulatory activity of AXs extracted from 10 cereal sources showed that the stimulatory effect of AXs on NO production by U937 cells seems to be associated with average molecular weight. More interestingly, it was noted that extracted and modified AXs had a significantly different effect on iNOS expression in U937 cells (p<0.05), suggesting that NO synthesis stimulated by AXs in vitro is closely mirrored by iNOS expression. CONCLUSIONS: As results of this study, the extraction process of AXs from corn bran and pentosan fraction of wheat flour was optimised. The conditions for modifying the molecular features of AXs were standardised. The experimental conditions for controlling the Mw distributions produced during the extraction and modification in order to enhance the immune-modulating activities of the AXs. The results of in vitro assessments should be useful in further understanding the mechanisms of the structure-activity relationship of AXs.

The possible role of volatile sulphur compounds in beer flavour has been investigated using simple analytical methods. These methods were studied and developed particularly for routine quality control use. Application of the procedures to the analysis of beer volatiles has indicated that, contrary to expectation, sulphur compounds play litt1e part in the flavour/aroma of beers designated as "sulphury". However the results obtained from this study suggests that a more important aspect of beer sulphur compounds may be in the role of flavour stability. Additionally the presence of dimethy1 sulphide in ale has shown it to be at a lower concentration than lager. Since the latter is produced by a different yeast and fermentation the presence of dimethyl sulphide may highlight fundamental differences in the raw materials and process. Finally suggestions are made for further work on beer flavour stability since this aspect could have fundamental repercussions on production economics and brewing procedures.

Tomato is widely grown popular vegetable across the globe and recognised as a versatile vegetable with high nutritive and functional properties. The majority of the tomato production processed into different types of products and thermal processing is extensively used. Several drawbacks have been identified in thermal processing including organoleptic and nutritional degradation. The study was conducted to investigate the impact of non-thermal processing technologies on total quality and health attributes of tomato juice in comparison to thermal processing. The physico-chemical properties of two tomato varieties Pitenza and Arvento were evalutaed and variety Pitenza showed a favorable processing properties including colour, texture and total soluble solids contents. Tomato juices with natural (4.3) and altered (3.9) pH levels were processed using high pressure processing (600 MPa/1 min) after blanching (90 oC/2 min) and superior product could be developed comparison to thermal processing (95 oC/20 min). However, maintenance of attributed quality over the extended period at high ambient temperature conditions (20 & 28 oC) still remains challenging. A mathematical model was developed to predict the redness and colour change of tomato juice after blanching in response to tomato cultivar, juice pH, blanching temperature and time. The validation results revealed that the model can be successfully used within the experimental limits. The influence of moderate intensity pulsed electric field processing (MIPEF) on enhancement of lycopene bioaccessibility of whole tomato fruits and the combined effect of thermal blanching, ultrasonication (US) and high intensity pused electric field processing (HIPEF) on further enhancement of lycopene bioaccessibility was investigated. The MIPEF treatment was effective to enhance the lycopene bioaccessibility of whole tomato fruits up to 9.6% comparison to 8.1% in untreated fresh tomato. Thermal processing and blanching showed significant reduction in lycopene bioaccessibility of tomato juice while combined treatment of MIPEF, blanching and HIPEF was successful in enhancing the lycopene bioaccessibility of tomato juice up to 15.6%.

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