Arsenic (As) exposure through water and As contaminated food in rural areas around the world is well documented. While there are accurate, precise, and even robust screening methods for on-site water analysis, the determination of toxic inorganic As (iAs, a class I carcinogen) in foodstuff has been made possible through methods based on mass spectrometry. No screening or field method for iAs in food has been established and, there is also a lack of screening and monitoring methods for human exposure to iAs. The objectives of this thesis were to develop and apply a robust, reliable and well established screening method which is field deployable for the measurement of iAs in rice and seaweed in addition to the total As metabolites in human urine resulting from exposure to inorganic As. Reported in this work is the development and application of optimised field deployable methods based on the Gutzeit reaction with the aid of a field test kit (FTK) for the determination of iAs in rice, rice-based products, edible seaweeds and seaweeds cultivated from their natural habitat. The methods involve simple sample extraction by boiling in nitric acid before analysis with the FTK. Results were obtained in under an hour with the FTK and further validated with speciation analysis by HPLC-ICP-MS (High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry). Analysis of 30 store-bought rice samples with the field method gave good reproducibility (± 12 %) for samples with variable As concentrations. The results were comparable to those obtained by HPLC-ICP-MS with no contribution from organoarsenicals. Screening analysis with the field method based on recent regulations for inorganic arsenic in rice also gave low false positive and false negative rates ( < 10 %) for violations against these regulations, an indication that the method can accurately identify samples that are above or below the recommended maximum contaminant limits for iAs in rice. Similarly, results from the seaweed analysis with the field method were also comparable to those from speciation analysis by HPLC-ICP-MS with limited bias between the set of data from both vii methods. Optimisation of extraction methods using a subset of samples gave 80-95% iAs recovery with no contribution from the organoarsenicals present in the samples. The determination of total As metabolites in urine from the exposure to iAs could not be done directly using the FTK. In this case, the method involved the use of UV photolysis with persulphate and titanium dioxide as oxidizing agents for the conversion of methylated As species (DMA) to the inorganic form before analysis with the FTK. A partial determination of DMA with the FTK in urine matrix was demonstrated but this needs to be studied further for the development of a robust field method for monitoring human exposure to iAs.

No description available.

No abstract available. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004

by Wong Ka Hing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Abstracts in English and Chinese. / Dedication --- p.i / Thesis committee --- p.ii / Acknowledgements --- p.iii / Abstract --- p.iv / Abstract (Chinese version) --- p.vi / Table of contents --- p.viii / List of tables --- p.xv / List of figures --- p.xviii / List of abbreviation --- p.xix / Chapter Chapter one: --- General introduction / Chapter 1.1. --- Definition --- p.1 / Chapter 1.2. --- Classification --- p.2 / Chapter 1.3. --- Potential food use of seaweeds --- p.7 / Chapter 1.4. --- Hong Kong seaweeds --- p.10 / Chapter 1.5. --- Sargassum species --- p.12 / Chapter 1.6. --- Hypnea species --- p.13 / Chapter 1.7. --- Ulva species --- p.14 / Chapter 1.8. --- Design of research project --- p.15 / Chapter Chapter two: --- "Effect of diflerent drying methods on proximate composition, amino acid profile and some physico-chemical properties of brown seaweeds, Sargassum hemiphyllum, Sargassum henslowianum and Sargassum patens" / Chapter 2.1. --- Introduction --- p.20 / Chapter 2.2. --- Materials and methods --- p.23 / Chapter 2.2.1. --- Sample preparation --- p.23 / Chapter 2.2.2. --- Proximate analysis --- p.26 / Chapter 2.2.2.1. --- Crude protein content --- p.26 / Chapter 2.2.2.2. --- Ash content --- p.26 / Chapter 2.2.2.3. --- Total dietary fiber (TDF) content --- p.27 / Chapter 2.2.2.4. --- Crude lipid content --- p.28 / Chapter 2.2.2.5. --- Carbohydrate content --- p.29 / Chapter 2.2.2.6. --- Moisture analysis --- p.29 / Chapter 2.2.3. --- Amino acid analysis --- p.30 / Chapter 2.2.3.1. --- "Amino acids excluding cystine, methionine and tryptophan" --- p.30 / Chapter 2.2.3.2. --- Cystine and methionine --- p.31 / Chapter 2.2.4. --- Physico-chemical properties --- p.32 / Chapter 2.2.4.1 --- Swelling capacity (SWC) --- p.32 / Chapter 2.2.4.2. --- Water holding capacity (WHC) --- p.32 / Chapter 2.2.4.3. --- Oil holding capacity (OHC) --- p.33 / Chapter 2.2.5. --- Statistical analysis --- p.34 / Chapter 2.3. --- Results and discussion --- p.34 / Chapter 2.3.1. --- Proximate composition --- p.34 / Chapter 2.3.2. --- Amino acid composition --- p.39 / Chapter 2.3.3. --- Physico-chemical properties --- p.42 / Chapter 2.3.4. --- Conclusions --- p.46 / Chapter Chapter three: --- "Effect of different methods on protein extarctability, in vitro protein digestibility and amino acid profile of seaweed protein concentrates isolated from brown seaweeds, Sargassum hemiphyllum, Sargassum henslowianum and sargassum patens" / Chapter 3.1. --- Introduction --- p.48 / Chapter 3.2. --- Materials and methods --- p.51 / Chapter 3.2.1. --- Sample preparation --- p.51 / Chapter 3.2.2. --- Extraction of seaweed protein concentrates --- p.51 / Chapter 3.2.3. --- Precipitation of seaweed protein concentrates --- p.52 / Chapter 3.2.4. --- Crude protein content analysis --- p.53 / Chapter 3.2.5. --- Extraction of total phenolic compounds --- p.53 / Chapter 3.2.6. --- Determination of total phenolic compounds --- p.54 / Chapter 3.2.7. --- In vitro protein digestibility --- p.55 / Chapter 3.2.8. --- Amino acid analysis --- p.56 / Chapter 3.2.9. --- Statistical analysis --- p.56 / Chapter 3.3. --- Results and discussion --- p.56 / Chapter 3.3.1. --- Effect of oven- or freeze-drying on protein extractability from seaweeds --- p.57 / Chapter 3.3.1.1. --- Total crude protein and total phenolic content in seaweeds --- p.57 / Chapter 3.3.1.2. --- "%Nitrogen, %protein, sample dry weight, amount of protein extracted and %yield of PCs" --- p.60 / Chapter 3.3.2. --- Effect of oven- and freeze-drying on protein quality of seaweed PCs --- p.62 / Chapter 3.3.2.1. --- Total phenolic content and in vitro protein digestibility of seaweed PCs --- p.62 / Chapter 3.3.2.2. --- Amino acid composition --- p.64 / Chapter 3.3.3. --- Conclusions --- p.67 / Chapter Chapter four: --- "Proximate composition, amino acid profile and some physico- chemical properties of some red (Hypnea charoides and Hypnea japonica) and green seaweeds (Ulva lactuca)" / Chapter 4.1. --- Introduction --- p.68 / Chapter 4.2. --- Materials and methods --- p.71 / Chapter 4.2.1. --- L Sample preparation --- p.71 / Chapter 4.2.2. --- Proximate analysis --- p.71 / Chapter 4.2.3. --- Amino acid profile --- p.73 / Chapter 4.2.4. --- Physico-chemical properties --- p.73 / Chapter 4.2.5. --- Statistical analysis --- p.74 / Chapter 4.3. --- Results and discussion --- p.74 / Chapter 4.3.1. --- Proximate composition --- p.74 / Chapter 4.3.2. --- Amino acid composition --- p.78 / Chapter 4.3.3. --- Physico-chemical properties --- p.81 / Chapter 4.3.4. --- Conclusions --- p.86 / Chapter Chapter five: --- In vitro protein digestibility and amino acid profile of seaweed protein concentrates isolated from some red (Hypnea charoides and Hypnea japonica) and green seaweeds (Ulva lactuca) / Chapter 5.1. --- Introduction --- p.88 / Chapter 5.2. --- Materials and methods --- p.89 / Chapter 5.2.1. --- Sample preparation --- p.89 / Chapter 5.2.2. --- Extraction and precipitation of seaweed PCs --- p.90 / Chapter 5.2.3. --- Crude protein analysis --- p.90 / Chapter 5.2.4. --- Extraction and determination of total phenolic contents --- p.90 / Chapter 5.2.5. --- In vitro protein digestibility --- p.91 / Chapter 5.2.6. --- Amino acid analysis --- p.92 / Chapter 5.2.7. --- Statistical analysis --- p.92 / Chapter 5.3. --- Results and discussion --- p.93 / Chapter 5.3.1. --- Protein extractability --- p.93 / Chapter 5.3.1.1. --- Crude protein and total phenolic contentin seaweeds --- p.93 / Chapter 5.3.1.2. --- "%Nitrogen, %protein, sample dry weight, amount of protein extracted and %yield of PCs" --- p.95 / Chapter 5.3.2. --- Protein quality --- p.97 / Chapter 5.3.2.1. --- Total phenolic content and in vitro protein digestibility of seaweed PCs --- p.97 / Chapter 5.3.2.2. --- Amino acid composition --- p.99 / Chapter 5.3.3. --- Conclusions --- p.103 / Chapter Chapter six: --- Biological evaluation on protein quality of seaweed protein concentrates isolated from Hypnea charoides and Hypnea japonica / Chapter 6.1. --- Introduction --- p.104 / Chapter 6.2. --- Materials and methods --- p.114 / Chapter 6.2.1. --- Sample preparation --- p.114 / Chapter 6.2.2. --- Extraction and precipitation of seaweed protein concentrates --- p.114 / Chapter 6.2.3. --- Diet preparation --- p.115 / Chapter 6.2.4. --- Rat bioassay --- p.117 / Chapter 6.2.5. --- Biological indices --- p.118 / Chapter 6.2.6. --- Statistical analysis --- p.119 / Chapter 6.3. --- Results and discussion --- p.119 / Chapter 6.3.1. --- Protein quality of seaweed PCs --- p.119 / Chapter 6.3.2. --- Weight of major organs --- p.126 / Chapter 6.3.3. --- Conclusions --- p.129 / Chapter Chapter seven: --- Functional properties of protein concentrates isolated from Hypnea charoides and Hypnea japonica / Chapter 7.1. --- Introduction --- p.130 / Chapter 7.2. --- Materials and methods --- p.136 / Chapter 7.2.1. --- Sample preparation --- p.136 / Chapter 7.2.2. --- Preparation of protein concentrates --- p.137 / Chapter 7.2.3. --- Nitrogen solubility --- p.137 / Chapter 7.2.4. --- Water and oil holding capacity --- p.138 / Chapter 7.2.5. --- Viscosity --- p.139 / Chapter 7.2.6. --- Emulsifying activities and emulsion stability --- p.140 / Chapter 7.2.7. --- Foam capacity and foam stability --- p.141 / Chapter 7.2.8. --- Statistical analysis --- p.142 / Chapter 7.3. --- Results and discussion --- p.142 / Chapter 7.3.1. --- Nitrogen solubility --- p.142 / Chapter 7.3.2 --- Wafer and oil holding capacity --- p.145 / Chapter 7.3.3. --- Viscosity --- p.147 / Chapter 7.3.4 --- Emulsifying activities and emulsion stability --- p.149 / Chapter 7.3.5. --- Foam capacity and foam stability --- p.153 / Chapter 7.3.6. --- Conclusions --- p.157 / Chapter Chapter 8: --- Conclusions --- p.158 / References --- p.160 / Appendix --- p.195 / Related publications --- p.202

by Li Yung Yung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 105-121). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.i / ABSTRACT (ENGLISH VERSION) --- p.ii / ABSTRACT (CHINESE VERSION) --- p.iv / TABLE OF CONTENTS --- p.v / LIST OF TABLES --- p.x / LIST OF FIGURES --- p.xi / LIST OF ABBREVIATIONS --- p.xiii / Chapter CHAPTER ONE --- INTRODUCTION / Chapter 1.1 --- Seaweed --- p.1 / Chapter 1.1.1 --- General Introduction --- p.1 / Chapter 1.1.2 --- Classification and Use of Seaweed --- p.1 / Chapter 1.1.3 --- Phycocolloids --- p.2 / Chapter 1.1.4 --- Hong Kong Seaweed --- p.3 / Chapter 1.1.4.1 --- Sargassum Species --- p.3 / Chapter 1.1.4.2 --- Padina Species --- p.5 / Chapter 1.2 --- Source and Production of Alginate --- p.8 / Chapter 1.2.1 --- Function of Alginate in Seaweed --- p.8 / Chapter 1.2.2 --- Chemical Structure of Alginate --- p.8 / Chapter 1.2.3 --- Alginate Production --- p.9 / Chapter 1.2.4 --- Isolation of Alginate --- p.13 / Chapter 1.2.5 --- Commercial Methods --- p.13 / Chapter 1.3 --- Application of Alginate --- p.14 / Chapter 1.3.1 --- Industrial Application --- p.14 / Chapter 1.3.2 --- Pharmaceutical Application --- p.16 / Chapter 1.3.3 --- Food Application --- p.17 / Chapter 1.3.3.1 --- Uses of Alginate in Food --- p.17 / Chapter 1.3.3.2 --- Safety --- p.19 / Chapter 1.4 --- Structure and Function Relationship of Alginate --- p.19 / Chapter 1.4.1 --- Physico-Chemical Properties --- p.21 / Chapter 1.4.1.1 --- M/G ratio --- p.21 / Chapter 1.4.1.2 --- Solution Properties --- p.21 / Chapter 1.4.1.3 --- Viscosity --- p.23 / Chapter 1.4.1.4 --- Molecular Weight --- p.27 / Chapter 1.4.2 --- Functional Properties --- p.27 / Chapter 1.4.2.1 --- Emulsion --- p.27 / Chapter 1.4.2.2 --- Gel Properties --- p.27 / Chapter 1.4.2.3 --- Mechanism of Gelation --- p.29 / Chapter 1.4.2.4 --- Gel Strength and Syneresis --- p.30 / Chapter 1.5 --- Physiological Effects --- p.32 / Chapter 1.5.1 --- Dietary Fibre --- p.32 / Chapter 1.5.2 --- Minerals --- p.32 / Chapter 1.6 --- Significance of the Present Study --- p.33 / Chapter CHAPTER TWO --- MATERIALS AND METHODS / Chapter 2.1 --- Seaweed Collection --- p.36 / Chapter 2.2 --- Sample Preparation --- p.36 / Chapter 2.3 --- Alginate Extraction --- p.38 / Chapter 2.3.1 --- Method A --- p.38 / Chapter 2.3.2 --- Method B --- p.38 / Chapter 2.3.3 --- Commercial Alginate --- p.39 / Chapter 2.4 --- Chemical Composition of Alginate --- p.41 / Chapter 2.4.1 --- Alginate Content --- p.41 / Chapter 2.4.2 --- Moisture Content --- p.41 / Chapter 2.4.3 --- Crude Protein Content --- p.41 / Chapter 2.4.4 --- Ash Content --- p.42 / Chapter 2.4.5 --- Monosaccharide Composition --- p.42 / Chapter 2.4.5.1 --- Acid Deploymerisation --- p.42 / Chapter 2.4.5.2 --- Neutral and Amino Sugar Derivatization --- p.42 / Chapter 2.4.5.3 --- Determination of Neutral Sugars by Gas Chromatography --- p.43 / Chapter 2.4.5.4 --- Uronic Acid Content --- p.44 / Chapter 2.4.6 --- Uronic Acid Block Composition --- p.44 / Chapter 2.4.6.1 --- "MG, MM and GG Block Determination" --- p.44 / Chapter 2.4.6.2 --- M/G Ratio Determination --- p.45 / Chapter 2.4.6.3 --- Phenol-Sulfuric Acid Method --- p.45 / Chapter 2.5 --- Physico-Chemical Properties of Alginate --- p.46 / Chapter 2.5.1 --- Viscosity --- p.46 / Chapter 2.5.1.1 --- Ostwald Viscometer --- p.46 / Chapter 2.5.1.2 --- Brookfield Viscometer --- p.47 / Chapter 2.5.2 --- Molecular Weight --- p.47 / Chapter 2.5.2.1 --- From Intrinsic Viscosity --- p.47 / Chapter 2.5.2.2 --- Gel Permeation Chromatography-Laser Light Scattering (GPC-LLS) --- p.48 / Chapter 2.6 --- Functional Properties of Alginate --- p.49 / Chapter 2.6.1 --- Emulsifying Activity (EA) and Emulsion Stability (ES) --- p.49 / Chapter 2.6.2 --- Gel Formation --- p.49 / Chapter 2.6.3 --- Gel Strength and Syneresis --- p.50 / Chapter 2.6.4 --- Application in Food ´ؤ Fruit Jelly --- p.52 / Chapter 2.7 --- Data Analysis --- p.53 / Chapter CHAPTER THREE --- RESULTS AND DISCUSSION / Chapter 3.1 --- Proximate Composition of Selected Seaweed --- p.54 / Chapter 3.1.1 --- Moisture Content --- p.54 / Chapter 3.1.2 --- Ash Content --- p.56 / Chapter 3.1.3 --- Crude Protein Content --- p.57 / Chapter 3.1.4 --- Carbohydrate Content --- p.58 / Chapter 3.2 --- Chemical Composition of Alginate Extracted from Two Different Methods --- p.58 / Chapter 3.2.1 --- Percentage Yield --- p.59 / Chapter 3.2.2 --- Alginate Content --- p.61 / Chapter 3.2.3 --- Moisture Content --- p.62 / Chapter 3.2.4 --- Ash Content --- p.62 / Chapter 3.2.5 --- Residual Protein Content --- p.63 / Chapter 3.2.6 --- Monosaccharide Composition of Alginate --- p.63 / Chapter 3.2.7 --- M/G Ratio --- p.66 / Chapter 3.2.8 --- Summary --- p.69 / Chapter 3.3 --- Comparative Studies of Physico-Chemical Composition of Alginate from Sargassum and Padina Species --- p.71 / Chapter 3.3.1 --- Block Composition and M/G Ratio --- p.71 / Chapter 3.3.2 --- Viscosity --- p.75 / Chapter 3.3.2.1 --- Intrinsic Viscosity ´ؤ Capillary Viscometer --- p.75 / Chapter 3.3.2.2 --- Solution Viscosity - Brookfield Viscometer --- p.79 / Chapter 3.3.2.2.1 --- Effect of Temperature --- p.79 / Chapter 3.3.2.2.2 --- Effect of Concentration --- p.81 / Chapter 3.3.2.2.3 --- Shear Thinning and Time Independent Effect --- p.82 / Chapter 3.3.3 --- Molecular Weight --- p.88 / Chapter 3.3.3.1 --- From Intrinsic Viscosity --- p.88 / Chapter 3.3.3.2 --- Gel Permeation Chromatograph-Laser Light Scattering (GPC-LLS) --- p.90 / Chapter 3.4 --- Comparative Studies of the Functional Properties of Extracted Alginate with Commercial Alginate --- p.93 / Chapter 3.4.1 --- Emulsifying Activity (EA) and Emulsifying Stability (ES) --- p.93 / Chapter 3.4.2 --- Gelling Properties --- p.95 / Chapter 3.4.2.1 --- Effect of Calcium Concentrations --- p.95 / Chapter 3.4.2.2 --- Gel Strength and Syneresis --- p.97 / Chapter 3.4.3 --- Application in Food --- p.99 / Chapter CHAPTER FOUR --- CONCLUSIONS --- p.103 / REFERENCES --- p.105 / RELATED PUBLICATION --- p.120