The poor growth of young rats fed fully supplemented diets containing raw soyabean appeared to be due to interference with local (intestinal) metabolism, resulting in apparently poor digestion and absorption of dietary nitrogen, coupled with changes in systemic intermediary metabolism, leaning to low overall retention of absorbed nitrogen and slightly incresed catabolism of body lipid. Low serum insulin concentrations and pancreas and small intestine enlargement were also evident. These changes were due to a number of anti-nutritional factors in soyabean: 1. Trypsin inhibitors (Kunitz + Bowman-Birk) depressed growth rate by reducing digestion and absorption of dietary nitrogen and interfering with retention of absorbed nitrogen. They also induced considerable enlargement of the pancreas. 2. The lectin inhibited growth primarily as a result of interference with retention of absorbed nitrogen. It also caused enlargement of the pancreas and of the small intestine. 3. Anti-nutritional factor/s, devoid of haemagglutinating or trypsin inhibitory activity, caused a loss of muscle and also possibly increased production and secretion of mucus in the small intestine. The poor growth of young soyabean-fed animals was thus due to the combined effects of these anti-nutritional factors. As the rats matured, the inhibitory effects of soyabean upon growth diminished and, after 16-24 weeks on the diet, were negligible. On the other hand, pancreas enlargement persisted upon long-term (up to 96 weeks) feeding with raw soyabean. Enlargement of the whole gastrointestinal tract was also evident upon prolonged soyabean feeding. With rats kept for more than 1 year on soyabean diet, there was apparently an increased incidence (approximately 15%) of pre-cancerous or cancerous changes in the pancreas. This amy have been due, in part, to a synergism between the lectin and trypsin inhibitors and unsaturated lipids. Aqueous heat-treatment greatly reduced but did not eliminate the anti-nutritional effects of soyabean. Pre-treatment of meal with hot aqueous ethanol was more effective.

Single chain Fv (scFv) and Fv antibody fragments derived from a monoclonal antibody recognising flagellae of Listeria species were cloned, expressed and purified from Escherichia coli. ScFv and Fv were purified by affinity chromatography on anti-flagellar and anti-hydrophil 2 affinity columns respectively. These fragments successfully compete with the parent monoclonal antibody for antigen binding but do not complete with a second monoclonal antibody which recognises a different epitope on the flagellae. The amount of antibody fragments expressed has been estimated as 0.1 mg 1-1 for scFc and 0.22 mg 1-1 for Fv. The relative affinities of the scFv, Fv and parental monoclonal antibody for binding to antigen were compared. Characterisation of ScFv by antigen binding profile showed it to have a sensitivity of the same order of magnitude as the parent monoclonal. Fv had a sensitivity one order of magnitude below that of the parent monoclonal and the scFv. ScFv was purified as a dimer and analysed by HPLC size exclusion chromatography. The variable heavy region (VH) sequence has been determined for a second anti-flagellar monoclonal antibody and this has been cloned into an E. coli expression vector. An IgM monoclonal antibody with broad range specificity to bacteria has been generated and the VH sequence determined.

Sensory analysis, that is the description of food or beverages by a panel of judges, has become increasingly important in the development of commercial foodstuffs. In general terms, sensory analysis involves scoring, for intensity, the adjectives of a vocabulary which adequately describes every nuance of sensory property found in the sample. The data from a sensory analysis of a set of samples are matrices of scores, one for each judge, with rows corresponding to adjectives, and columns to samples. This can be interpreted as a set of configurations, one for each judge, where points correspond to samples, and dimensions to adjectives. The question of how to combine the scores by each judge to summarise the information on the samples, is of particular interest. This thesis concentrates on combining judge scores by generalized Procrustes analysis, the method of simultaneously matching a set of configurations by translation, rotation/reflection and scaling. This analysis has intrinsic appeal as it allows each judge to have his own interpretation of the adjectives. The only constraint is that the judges must place samples in the same relative positions within their own private scoring schemes. The asymptotic distribution of the residual sum of squares after a generalized Procrustes analysis is discussed, and the sum of squares before transformation is shown to partition into sums of squares for translation, rotation/reflection scaling and a residual. Therefore, the effects of the Procrustes transformations can be presented in an ANOVA format. The use of complementary pair-wise Procrustes rotation is shown to be made redundant by a modification to the generalized Procrustes analysis, which gives a Euclidean representation of the judges. A worked example illustrates the advantage, over the panel mean, of a generalized Procrustes analysis, and a summary of the sample information by the consensus configuration.

Physiological studies of type cultures of Neurospora crassa, N. sitophila, and N. intermedia in terms of growth on bread, effects of heat flashes, water activity, food additives and viability of stored conidia revealed no differences in either environmental or substrate preferences among the species on which a classification could be based. 345 putative wild isolates of Neurospora were collected from a wide variety of sources - silage, Indonesian ontjom, wheat grains, flour, bread, crumpets, bakery air and bakery dust. These all grew more vigorously than the type cultures. They were compared with respect to morphological traits such as conidial colour and size, and degree of protoperitheciality, but these features again proved inadequate to distinguish between species. The wild isolates were crossed with tester strains which were derived or synthesized from isolates in the collection and authenticated with reference strains from the Fungal Genetics Stock Center and the Commonwealth Mycological Institute. The times required in these crosses for perithecium formation and ascospore ejection, and the perithecial pattern and percentage of dark-coloured ascospores produced were investigated. The latter proved to be an unambiguous and highly reproducible diagnostic character for species delineation. Neurospora crassa accounted for the bulk of the collection, conflicting with the popular view that N. sitophila is the principal Neurospora contaminant of bread. Only heterothallic strains of both mating types of N. crassa, N. sitophila, and N. intermedia were represented. Based on six characteristics (conidial colour, mating-type, protoperitheciality and percentage dark-coloured ascospores with the three species testers), the isolates of bakery origin were grouped into 112 individual strains. Such variability indicated that there was continual infection in these bakeries from a large population of strains estimated from analysis based upon the Poisson distribution to be about 170. Based on this finding, a model of the probable infection cycle of Neurospora in bakeries is described.

Seven hundred and seventeen yeasts isolated from samples of sulphited and unsulphited sausage, skinless sausage, minced beef, and ingredients intended for sausage manufacture, as well as air and equipment in a sausage factory were characterised in detail. Debaryomyces hansenii was the most commonly occurring yeast in the majority of samples of sausage and minced beef, followed by Candida zeylainoides and Pichia membranaefaciens. The presence of sulphite did not appear to influence the overall numbers or range of yeasts in sausage but did affect their relative proportions such that the incidence of D. hansenii was higher and that of certain Cryptoccoccus and Rhodotorula spp. was lower in samples containing the preservative. The heat treatment of skinless sausages during processing appeared to reduce the incidence of D. hansenii. The factory survey showed that the meat intended for sausage manufacture and also other ingredients as well as equipment harboured the same range of yeasts as were found in the finished product. A yeast flora dominated by Trichosporon cutaneum was isolated from pig carcasses immediately following slaughter. This flora was found to be confined largely to the equipment and air of the slaughter area and lairage. In general, the yeast flora of sausage was non-fermentative but could assimilate a wide range of carbohydrates. Selected strains of C. curvata, C. lipolytica var. lipolytica, C. zeylanoides, Cr. albidus, D. hansenii, P. membranaefaciens and Torulopsis candia were shown to synthesise either extra cellular lipases and/or amylases but not proteases in broth culture. Sulphite binding compounds, principally acetaldehyde, were produced in lab lemco broth (pH 7.0) containing sulphite (500 mug g-1) during the exponential phase of growth of representative strains of D. hansenii, C. zeylanoides, P. membranaefaciens and T. candida but not Cr. albidus var. albidus and Rh. rubra. The extent of sulphite binding in minced pork- belly supplemented with sulphite (500 mug g-1) was appreciably greater in samples inoculated with D. hansenii than in those inoculated with representatives of the other members of the microbial association, Brochothrix thermosphacta, Lactobacillus sp. and a pseudomonad. The content of sulphite binding agents in minced pork was found to be positively related (r = 0.98, 0.92 at 1 and 15°C respectively) to the size of the yeast population. The concentration of acetaldehyde in stored sausages obtained from a factory and also those obtained from retail outlets was correlated with the concentration of bound sulphite (r = 0.89). The rate and extent of sulphite binding and acetaldehyde production was fastest during the exponential phase of yeast growth in sausages.

The microbial associations that developed in commercially produced sulphited and unsulphited sausages during storage for up to 8 days at a variety of temperatures were identified. Such associations were comprised of domiinant, e.g. Brochothrix thermosphacta, yeasts and lactic acid bacteria, or minor, e.g. Pseudomonadaceae and Enterobacteriaiceae, groups. A detailed analysis of numerous isolates of the previously-ignored Gramnegative microflora using computer-assisted numerical techniques revealed that sulphite concentratioin influenced the composition of the Enterobacteriaceae but not the pseudomonads. A method was developed for the assay of free and bound sulphur IV oxospecies in culture media or meat-based samples. It was superior to existing techniques and demonstrated limited irretrievable - by oxidation - and extensive reversible - by binding - loss of sulphite preservative from freshly manufactured and stored sausage. Selected micro-organisms isolated from sausage were tested for their tolerance of free and bound sulphur IV oxospecies in batch and "turbidometer" culture under various conditions. In general this technique reflected the elective/selective role of sulphite in sausage and allowed the microbial association to be defined more clearly in terms of tolerance of the active preservative. The incidence and level of contamination of sausage and its ingredients with Salmonella was established using a 'most-probable number' method. Despite a high incidence of contamination of most of the meat ingredients and finished product with these organisms, the level of infection - with the exception of mechanically recovered meat - was low. Thus the role of sulphur IV oxospecies in determining the fate of these food poisoning organisms in sausage or culture media was assessed by deliberate infection with rifampicinresistant Salmonella mutants. With a view to extending the shelf life of fresh sausage, a limited survey of adjuncts or alternative "preservatives" to sulphite using pilot-scale batches of sausage meat was done.

No description available.

The practical work described in this thesis falls into four distinct subject areas: HPLC, tea liquor fractionation, mass spectrometry, and NMR and IR. The practical work, is therefore written in four chapters, each chapter having its own introduction, results and discussion, and experimental sections. The work is concerned with the analysis of black tea liquor, its aim being to provide an analytical input into a larger project, being carried at NRI (Natural Resources Institute), on the statistical evaluation of tea quality.

The synthesis and use of monoacylglycerols in food systems havc been reviewed. The use of monoacylglycerols alone or in combination with free fatty acids as food preservatives has been discussed. Model systems have been devised to produce monoacylglycerols (MAGs) from butter and Shea oils with two strains of Penicillium roquefortii, FRR 2456 (isolated from a spoilt melon) and Wisbey PJ (a commercial dairy strain) A semi-micro method was developed using Preparative Thin Layer Chromatography (PTLC) and Gas Chromatography - Mass Spectrometry (GC-MS) of the MAG trimethylsilyl ether derivatives to determine the identification, fatty acid composition and structural isomers of the individual MAG. The main monoacylglycerols produced by spores and emerging mycelium were 1(3)-monoacylsn-lycerols (in suspension culture). Monopalmitin was the major MAG from butter and Shea oils. Monoacylglycerols produced by fungal mycelium (in solid-state culture) were mainly the 1 (3 )-monoacyl-sn-glycerols although approximately 30% were present as 2-monoacyl-snglycerols. Again the main MAG was monopalmitin. It suggested that P. roquefortii produced two lipases, one during germination with specificity to the sn-2 position in the original triacylglycerols (TAGs) and one L3-specific during growth of the fungal mycelium. In addition, flavour compounds, methyl ketones and y-lactones, were found in solid-state culture. The composition of the MAGs formed by lipolysis using a commercial lipase (E.C.3.1.1.3) with 1,3- specificity gave the expected 2-isomers when butter oil was the substrate but gave 1 (3)monostearin rather than the expected 2-monoolein when Shea oil was the substrate. It suggested that acyl migration occurred due to the reactive nature of the original oleate group at the sn-2 position in the Shea oil TAGs. There were no significant differences with fungal strain or temperature of incubation (10 °C and 25°C) on the composition of the MAGs. The mechanism of formation of MAGs from butter and Shea oils has been discussed. It has been suggested that l(3)-MAGs together with free fatty acids may be part of a natural antimicrobial system in high pH foods such as blue mould-ripened cheese where growth of foodborne pathogens such as Listeria monoGytogcnes can be a problem from time to time

No description available.