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Water and lipid-soluble meat flavour precursors are gradually formed post-mortem via biochemical reactions. Storage time and temperature can affect final flavour precursor concentrations which in turn will affect the sensory quality of cooked meat. Selected key flavour precursors were monitored in Bison bison longissimus dorsi muscles from six animals stored at 2, 4, 8, 15 and 21 days at 4°C, in order to evaluate the effect of post-mortem conditioning on the formation of flavour precursors. Results were correlated with sensory data obtained using quantitative descriptive analysis with 8 trained panelists. While lipid-soluble flavour precursors remained mostly unchanged, significant increases (P<0.05) in concentrations of water-soluble flavour precursors including reducing sugars (eg. ribose, xylose), free amino acids (eg. valine, leucine) and adenosine-5’-triphosphate (ATP) degradation products (eg. inosine and hypoxanthine) were obtained with chilled storage conditioning post-mortem. The overall balance and correlations of water-soluble flavour precursors with storage day 15 and 21 were reported and can potentially impact the eating quality of cooked bison meat.

A novel type of white light emitting semiconductor quantum dot was characterized at the ensemble and single-molecule level. This kind of semiconductor nanocrystal can be made into white light emitting diodes, which have the potential to replace conventional lighting sources. The quantum dots used in this thesis consisted of a cadmium selenide (CdSe) core, capped with ZnS, and have a surface polymer coating of poly(acrylic acid) (PAA). We have characterized the quantum dot size distribution by using dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-Vis spectroscopy. Based on these measurements, it is clear that the white quantum dots are polydisperse, with a core size of 2.4 ± 0.5 nm, though the polymer coating swells considerably in aqueous solution. In order to explore the optical properties, the absorption and emission spectra of the ensemble quantum dots solution were measured and compared to “standard” commercial quantum dots. The emission spectrum of the white quantum dots showed two peaks, a strong blue emission peak and a weaker red emission peak. The fluorescence quantum yield of the white quantum dots was found to be less than that of commercial quantum dots. To explore the behavior of individual quantum dots, spatially-resolved single-molecule images were obtained by a dual-view single molecule fluorescence microscopy with a beam splitter which can separate the emission into red and blue components. It was found that individual white CdSe nanocrystals have a broad emission spectrum and the samples did not consist of a mixed population of red emitters and blue emitters. These results suggest that these white light emitting quantum dots can be used for pure white light LEDs and are a good candidate for the replacement for conventional lighting sources.

Background During the first stages of development human infants are either fed human milk or human milk substitutes (infant formulas). The composition of infant formulas and human milk differ drastically, including a difference in protein constituents and bacterial load. Due to the high global frequency of infant formula use, the humanization of infant formulas to better reflect the complex nature of human milk is warranted. To better understand the role of human milk components, the fate and function of a key bacterial sensor in human milk, soluble CD14, was determined. Additionally, the microbiome of human milk was analyzed from a metagenomic standpoint in an attempt to determine which types of bacteria are present in human milk and what their potential biological function might be. Results In rodent models, ingested sCD14 persisted in the gastrointestinal tract and was transferred intact into the blood stream. Once transferred to the blood, ingested sCD14 retained its ability to recognize lipopolysaccharide and initiate an immune response in pups. This transfer of sCD14 across the epithelial barrier was also observed in human cells in vitro, where it appears to be dependent on Toll-like receptor 4. Using Illumina sequencing and the MG-RAST pipeline, the human milk metagenome of ten mothers was sequenced. DNA from human milk aligned to over 360 prokaryotic genera, and contained 30,128 open reading frames assigned to various functional categories. The DNA from human milk was also found to harbor immune-modulatory DNA motifs that may play a significant role in immune development of the infant. Conclusions Given the complex nature of human milk in comparison to its bovine or plant based substitutes, the results presented in this thesis warrant future modification of infant formulas to include non-nutritive bioactive components. Current human milk components not yet present in infant formulas include the diverse microbiome of human milk, the immune-modulatory DNAs which those microbes harbor, and bioactive human proteins such as sCD14.

Water and lipid-soluble meat flavour precursors are gradually formed post-mortem via biochemical reactions. Storage time and temperature can affect final flavour precursor concentrations which in turn will affect the sensory quality of cooked meat. Selected key flavour precursors were monitored in Bison bison longissimus dorsi muscles from six animals stored at 2, 4, 8, 15 and 21 days at 4°C, in order to evaluate the effect of post-mortem conditioning on the formation of flavour precursors. Results were correlated with sensory data obtained using quantitative descriptive analysis with 8 trained panelists. While lipid-soluble flavour precursors remained mostly unchanged, significant increases (P<0.05) in concentrations of water-soluble flavour precursors including reducing sugars (eg. ribose, xylose), free amino acids (eg. valine, leucine) and adenosine-5’-triphosphate (ATP) degradation products (eg. inosine and hypoxanthine) were obtained with chilled storage conditioning post-mortem. The overall balance and correlations of water-soluble flavour precursors with storage day 15 and 21 were reported and can potentially impact the eating quality of cooked bison meat.

The generation of macrophages requires the coordinated responses to stimulatory and inhibitory signals that cell receive from their environment. While the up-regulation of macrophage production and survival is essential to fortify the immune system, their down-regulation is also vital to prevent macrophage related diseases and malignancy. Previous studies in goldfish showed that primary kidney macrophages release endogenous growth inducing factors into proliferative phase supernatant, which up-regulate their proliferation and survival. In this thesis, the effect of senescence phase supernatant (collected from goldfish primary kidney macrophage cultures) on goldfish primary kidney macrophages proliferation, survival and its impact on the ability of macrophages to tolerate H2O2 was analyzed. The results showed that the senescence phase supernatant down-regulated the proliferation and survival, and decreased the chemical tolerance of the cells. This indicated that the goldfish primary kidney macrophages promote targeted control of their proliferation and survival by secreting endogenous growth inhibitory factors in the senescence phase supernatant. / Physiology, Cell and Development Biology

The thermal processing of milk changes the composition and surface properties of the colloidal particles present and alters the physical properties of the milk. Whilst some changes such as those used to improve the texture of products such as yoghurt and are desirable, others such as gel formation during the manufacture of Ultra-High Temperature milk are highly undesirable. This work aims to characterize the effects of milk composition and pH on the chemical and physical changes that occur when milk is heated in order to understand and control the effect of thermal processing on the functional properties of the milk. Particularly important are: (i) the changes to the integrity of the casein micelles and the extent to which they are reversible on cooling of the heated milk, (ii) the changes to the speciation of the components of the serum as they re-equilibrate in response to the changed environment during heating and on cooling, (iii) the heat-induced denaturation of the whey proteins, (iv) the interaction between the components of the micelles and those in the milk serum, particularly those interactions that lead to aggregation or other changes that affect the functional properties of the milk on heating. This project includes thermal treatment (90&deg;C/10 min) of control skim milk solutions (9% Milk Solids Non Fat) with or without addition of calcium chelating agents (orthophosphate (Pin) & Ethylenediaminetetraacetic acid (EDTA)) and concentrated skim milk solutions (up to 21% MSNF). The pH range chosen was 6.2 to 7.2. Almost all of the studies on heat stability to date have been carried out by heating the milk and determining the changes that have occurred after the milk is cooled. This project is focussed on the direct measurements in real time of the changes that occur at the exact temperature. The experimental techniques included pH, calcium activity and 31P NMR measurements at high temperatures to investigate the consequences to the change in mineral speciation, Size Exclusion Chromatography in combination with SDS-PAGE analysis for protein speciation during heating and Diffusing Wave Spectroscopy and viscosity measurements to determine the heat stability of milk systems. pH and calcium activity decreased with increase in temperature for all the milk systems studied. These changes were largely reversible as enough time was given for equilibration. pH and calcium activity changes during heating are a function of milk composition. The quantity, size and the composition of the protein aggregates present in the serum phase after mild centrifugation (~33,000g) of heated (90&deg;C/10min) milk solutions were found to be a function of pH and milk composition (including the consequent differences in speciation of the components of milk). DWS and the viscosity measurements showed that pH at the temperature of heating is one of the primary determinants in influencing the aggregation of the proteins, which led to thermal stability of milk systems. Hence, changing the milk composition resulted in differences in pH at the temperature of heating, which led to different behaviours of heat stability of milk systems. Careful control of the composition of milk and thereby the pH at the temperature of heating allows a greater control of thermal stability of milk systems.

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 150-159). Also available on the Internet.

Thesis (Ph. D.)--University of Oregon, 2000. / Title from title screen. Paging within document: xvii, 167 p. : ill. Includes vita and abstract. Includes bibliographical references (p. 149-167).