Bioactive Compounds in Foods

Description

Inherent toxicants and processing contaminants are both non-essential, bioactive substances whose levels in foods can be difficult to control. This volume covers both types of compound for the first time, examining their beneficial as well as their undesirable effects in the human diet. Chapters have been written as individually comprehensive reviews, and topics have been selected to illustrate recent scientific advances in understanding of the occurrence and mechanism of formation, exposure/risk assessment and developments in the underpinning analytical methodology. A wide range of contaminants are examined in detail, including pyrrolizidine alkaloids, glucosinolates, phycotoxins, and mycotoxins. Several process contaminants (eg acrylamide and furan), which are relatively new but which have a rapidly growing literature, are also covered. The book provides a practical reference for a wide range of experts: specialist toxicologists (chemists and food chemists), hygienists, government officials and anyone who needs to be aware of the main issues concerning toxicants and process contaminants in food. It will also be a valuable introduction to the subject for post-graduate students. Contents Contributors PART ONE: NATURAL TOXICANTS 1 Introduction 1.1 Different perceptions of chemicals in food 1.2 Residues and contaminants in foods 1.3 Natural toxicants in foods 1.4 Developments in analytical methodology 1.5 Emerging risks 1.6 Bioactive compounds in foods 2 Pyrrolizidine Alkaloids Summary 2.1 Introduction 2.2 The pyrrolizidine alkaloids 2.3 Occurrence 2.3.1 Formation and function 2.4 Exposure 2.4.1 Contamination of foods 2.4.2 Pyrrolizidines in herbal preparations 2.5 Regulations 2.6 Toxicity and metabolism 2.6.1 General toxicity 2.6.2 Metabolism 2.6.3 Carcinogenicity and mutagenicity 2.7 Analytical methods 2.7.1 Extraction 2.7.2 Gas chromatography 2.7.3 High performance liquid chromatography 2.7.4 Other methods Conclusions References 3 Glucosinolates Summary 3.1 Introduction 3.2 Nature and occurrence 3.3 Biosynthesis 3.3.1 Amino acid modification 3.3.2 Conversion of amino acids 3.3.3 Secondary transformations 3.4 Hydrolysis 3.4.1 Myrosinase 3.4.2 Hydrolysis products 3.5 Analytical methods 3.5.1 Total glucosinolates 3.5.2 Individual glucosinolates 3.5.3 Breakdown products 3.6 Biological effects 3.6.1 Anticarcinogenicity 3.6.2 Toxicity 3.7 Taste versus health 3.8 Responses to stress factors 3.9 Effects of processing Conclusions References 4 Phycotoxins in Seafood Summary 4.1 Introduction 4.2 Causative and vector organisms 4.3 Classification of phycotoxins 4.4 The saxitoxin (STX) group (PSP) 4.4.1 The toxins causing PSP: the saxitoxin family 4.4.2 Toxic effects 4.5 The okadaic acid (OA) group (DSP) 4.5.1 The toxins causing DSP: okadaic acid and the dinophysistoxins 4.5.2 Toxic effects 4.6 The domoic acid (DA) group (ASP) 4.6.1 The toxins causing ASP (DAP): domoic acid and its isomers 4.6.2 Toxic effects 4.7 The azaspiracid (AZA) group (AZP) 4.7.1 The toxins causing AZP: the azaspiracids 4.7.2 Toxic effects 4.8 The brevetoxin (BTX) group (NSP) 4.8.1 The toxins causing NSP: the brevetoxins 4.8.2 Toxic effects 4.9 The ciguatera toxin (CTX) group (CFP) 4.9.1 The toxins causing CFP 4.9.2 Toxic effects of CTXs 4.10 Other phycotoxins 4.10.1 The pectenotoxin group 4.10.2 The yessotoxin group 4.10.3 The cyclic imine group 4.10.4 The cyanobacterial toxins 4.10.5 Miscellaneous phycotoxins 4.11 Detection of phycotoxins in seafood and algae 4.11.1 Assays and analyses 4.11.2 Mammalian bioassays 4.11.3 Instrumental (physico-chemical) analysis 4.11.4 In vitro assays 4.12 Depuration of phycotoxins 4.12.1 Natural depuration 4.12.2 Studies on cooking as a method of depuration 4.12.3 The effects of freezing and chilling 4.13 Monitoring and regulation 4.13.1 Phytoplankton monitoring 4.13.2 Monitoring of shellfish tissues for toxicity 4.13.3 Risk analysis 4.14 Future prospects 4.15 A note on the IOC harmful algal bloom programme Acknowledgements References 5 Mushroom Toxins Summary 5.1 Introduction 5.2 Poisonous mushrooms 5.2.1 Amatoxins, phallotoxins and virotoxins 5.2.2 Orellanine 5.2.3 Muscarine 5.2.4 Ibotenic acid and muscimol 5.2.5 Psilocybin, psilocin 5.2.6 Coprine 5.3 Edible mushrooms 5.3.1 Gyromitrin 5.3.2 Agaritine and other phenylhydrazines References 6 Mycotoxins Summary 6.1 Introduction 6.1.1 Mycotoxins and their study 6.1.2 Mycotoxins and fungi 6.1.3 Sampling and detection 6.1.4 Significance and control 6.2 Aflatoxins 6.2.1 Chemical properties 6.2.2 Analytical methods 6.2.3 Occurrence in raw materials and processed foods 6.2.4 Toxicology 6.2.5 Regulation and control 6.3 Ochratoxin A 6.3.1 Chemical properties 6.3.2 Analytical methods 6.3.3 Occurrence in raw materials and processed foods 6.3.4 Toxicology 6.3.5 Regulation and control 6.4 Deoxynivalenol and the trichothecenes 6.4.1 Chemical properties 6.4.2 Analytical methods 6.4.3 Occurrence in raw materials and processed foods 6.4.4 Toxicology 6.4.5 Regulation and control 6.5 Zearalenone 6.5.1 Chemical properties 6.5.2 Analytical methods 6.5.3 Occurrence in raw materials and processed foods 6.5.4 Toxicology 6.5.5 Regulation and control 6.6 Fumonisins 6.6.1 Chemical properties 6.6.2 Analytical methods 6.6.3 Occurrence in raw materials and processed foods 6.6.4 Toxicology 6.6.5 Regulation and control 6.7 Patulin 6.7.1 Chemical properties 6.7.2 Analytical methods 6.7.3 Occurrence in raw materials and processed foods 6.7.4 Toxicology 6.7.5 Regulation and control 6.8 Other mycotoxins 6.8.1 Citrinin 6.8.2 Sterigmatocystin 6.8.3 Cyclopiazonic acid 6.8.4 Moniliformin 6.8.5 Alternaria toxins References 7 Phytoestrogens Summary 7.1 Introduction 7.2 The structure of phytoestrogens 7.3 Occurrence and levels in plant materials 7.3.1 Defining phytoestrogens by class and structure 7.3.2 Compositional databases 7.3.3 Factors affecting isoflavone content in soya 7.3.4 Other possible phytoestrogens 7.4 Measurement of individual phytoestrogens 7.4.1 Traditional approaches 7.4.2 Mass spectrometry 7.4.3 Immunoassays 7.4.4 Online bioactivity assays 7.5 Measurement of oestrogenicity 7.6 Oestrogen receptors 7.6.1 Introduction 7.6.2 Receptors – ERα and ERβ 7.6.3 Oestrogen receptor-binding assays Conclusions References 8 Carboline Alkaloids Summary 8.1 Introduction 8.2 Chemistry, synthesis, and formation of β-carboline alkaloids 8.3 Analysis of carboline alkaloids 8.3.1 Sample preparation 8.3.2 Chromatographic analysis and detection 8.4 Occurrence of β-carboline alkaloids in foods and exposure 8.4.1 THβCs in foods 8.4.2 βCs in foods 8.5 Factors influencing the presence of carbolines in foods 8.6 Biological activity and toxicology of β-carbolines Conclusions and future directions Acknowledgments References PART TWO: MAN-MADE COMPONENTS 9 Naturally Occurring Nitrates and Nitrites in Foods Summary 9.1 Introduction 9.2 Methods of analysis 9.2.1 Sampling and storage 9.2.2 Extraction 9.2.3 Spectrophotometric methods 9.2.4 Chromatographic methods 9.2.5 Other methods 9.3 Incidence and levels of occurrence 9.3.1 Vegetables 9.3.2 Fruits 9.3.3 Milk and dairy products 9.3.4 Cereals and bread 9.3.5 Fresh meat 9.3.6 Drinking water 9.4 Toxicity of nitrate and nitrite 9.5 Dietary exposure 9.6 Regulations Conclusions References 10 Acrylamide in Heated Foods Summary 10.1 Introduction 10.2 Mechanism of formation in foods 10.2.1 Mechanistic pathways 10.2.2 Formation in foods during thermal processing 10.2.3 Kinetic modelling 10.3 Methods of analysis 10.3.1 Sample preparation 10.3.2 Chromatographic separation 10.3.3 Detection 10.3.4 Colour spectrophotometer 10.3.5 Computer vision-based image analysis 10.3.6 Near-infrared spectrophotometer 10.4 Occurrence in foods and exposure assessments 10.5 Biological effects 10.6 Methods to reduce formation in foods 10.6.1 Potato products 10.6.2 Bakery products References 11 Furan in Processed Foods Summary 11.1 Introduction 11.2 Formation and mechanisms 11.2.1 Model studies 11.2.2 Formation mechanisms 11.2.3 Food products 11.2.4 Mitigation concepts 11.3 Levels of occurrence and exposure 11.3.1 Data collection 11.3.2 Coffee 11.3.3 Baby food and other dietary sources 11.3.4 Domestic cooking 11.3.5 Dietary exposure 11.4 Methods of analysis 11.4.1 Sample preparation 11.4.2 Sampling methods 11.4.3 GC-MS analysis 11.4.4 Method validation 11.4.5 On-line monitoring Concluding remarks References 12 Chloropropanols and their Fatty Acid Esters Summary 12.1 Introduction 12.1.1 Historical perspective: 1979—2000 12.1.2 Scope of chapter 12.2 Toxicology 12.2.1 3-MCPD 12.2.2 Dichloropropanols 12.2.3 Chloroesters 12.3 Analytical methods 12.3.1 Chloropropanols 12.3.2 Chloroesters 12.4 Occurrence 12.4.1 Chloropropanols 12.4.2 Chloroesters 12.5 Mechanisms and precursors 12.5.1 From hydrochloric acid and glycerol/acylglycerols 12.5.2 From hypochlorous acid and allyl alcohol 12.5.3 Formation in thermally processed foods and ingredients 12.5.4 Mechanisms involving enzymes 12.5.5 Other mechanisms of interest 12.6 Reactions of Chloropropanols 12.6.1 Stability of MCPDs 12.6.2 Reactions of 3-MCPD 12.7 Mitigation 12.8 Exposure 12.8.1 3-MCPD 12.9 Regulatory status Conclusions and future prospects References 13 Heterocyclic Amines Summary 13.1 Introduction 13.2 Formation of heterocyclic amines 13.2.1 Model systems 13.2.2 Conditions for formation in meats 13.2.3 Food sample analysis 13.3 Sample extraction 13.3.1 Chromatography and detection 13.3.2 Mass spectrometry 13.3.3 GC/MS 13.3.4 LC/MS 13.3.5 High pressure LC-MS/MS 13.3.6 Capillary electrophoresis 13.4 Incidence and occurrence 13.4.1 Pan residues and food flavors 13.4.2 Modifying cooking practices to reduce the formation of heterocyclic amines 13.5 Exposure assessement 13.6 Risk 13.7 Regulations Conclusion Acknowledgments References 14 Polycyclic Aromatic Hydrocarbons Summary 14.1 Occurrence and mechanism of formation 14.1.1 Definition 14.1.2 Sources of PAHs 14.1.3 Sources of PAHs in foods 14.1.4 Environmental fate and degradation 14.2 Methods of analysis 14.2.1 Current status 14.2.2 Analytical methods – forward look 14.3 PAHs in food, exposure assessment and health effects 14.3.1 PAHs in food and dietary intake 14.3.2 Health effects and risk assessments 14.4 Regulations References Index