CURRENT TOPICS IN FLAVOURS AND FRAGRANCES

Current Topics in Flavours and Fragrances

Towards a New Millennium of Discovery

Edited by

Karl A.D. Swift Quest International, Ashford, Kent, U.K.

SPRINGER SCIENCE+BUSINESS MEDIA, B.V.

A CLP. Catalogue record for this book is available from the Library of Congress.

ISBN 978-94-010-5775-2 ISBN 978-94-011-4022-5 (eBook) DOI 10.1007/978-94-011-4022-5

Printed on acid-free paper

The cover illustration displays the solid-state conformation of a-cycloaltrin (a-CA) in different forms: the molecule adopts a conformation of 3-fold rotational symmetry with a unique alternating sequence of 4 C , and ! C 4 altropyranose chair geometries (upper left model, space group P63), resul­ting in banana-shaped disaccharide units, of which one is represented as a space-filling CPK-type model (lower left entry). In the crystal lattice the compact molecules are stacked in transposed lay­ers (upper right, water molecules left off for clarity). Each a-CA molecule is embedded into a matrix of 21 water molecules (lower right, view along the hexagonal c-axis). The space filling models reve­al a-CA to be devoid of a central 'through-going' cavity. The graphics were generated using Brickmann's MOLCAD molecular modeling program; for further information see the web-pages at thttp://caramel.oc.chemie.tudarmstadt.de/immel/molcad/Gallery.htmror 'S. Immel, G.E. Schmitt, and F.W. Lichtenthaler: a-Cycloaltrin: Conformation and Properties in the Solid-State and Aqueous Solution/, pp. 41-48 of this volume.

All Rights Reserved © 1999 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1999 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.

CONTENTS

Preface xiii

Introduction 1 Karl A. D. Swift, Quest International

The Total Synthesis of Synthetically Interesting Perfumery Natural Products 5 Karl A. D. Swift, Quest International

1. Introduction 5 2. Vetiver Oil 6

2.1. Introduction 6 2.1.1. Khusimone 6 2.1.2. ~-Vetivone 13

3.cnnsOiI 19 3.1. Irones 19

4. Patchouli Oil 23 4.1. PatchOldi Alcohol 23

5. Osmanthus Oil 27 5.1. Theaspirones 27

6. Abbreviations 31 7. References 31

Advances in the Transition Metal (Rh, Ru)-BINAP-Catalysed Asymmetric Synthesis of Chiral Compounds for Flavours and Fragrances and Their Associated Sensory Properties 33 Takeshi Yamamoto, Takasago International Corporation

1. Introduction 33 2. Asymmetric synthesis of chiral compounds for flavours and fragrances catalysed by (Rh, Ru)-BINAP complex and their associated sensory properties 34

2.1. Rh-BINAP-Catalysed asymmetric isomerisation of allylamine (Synthesis of I-menthol and citronellyl derivatives) 34

2.1.1. I-Menthol 34 2.1.2. I-Citronellol 36 2.1.3. I-LaurinaI™ (l-7-Hydro~:ycitronellal) and Aurantiol 38

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2.1.4. Damascone-related compounds 39 2.1.5. l-cis-Roseoxide, Dihydroroseoxide 40 2.1.6. Citrus-related compounds 41 2.1.7. d-Norlimbanol™ and its homologues 43

2.2. Asymmetric hydrogenation of olefins catalysed by Ru-BINAP complexes 45

2.2.1. (3S)-(-)-(6E)-2,3-dihydrofamesol 45 2.2.2. I-Muscone 46 2.2.3. Alkylcyclo~ntanones and 8-lactones 48 2.2.4. Brahmanol 50 2.2.5. Lilial™-related compounds 51 2.2.6. 2-Methylbutyric acid and its ethyl esters 52

2.3. Asymmetric hydrogenation of ketones catalysed by Ru-BINAP complexes 53

2.3.1. (R)-Styrallyl acetate 53 2.3.2. l-Matsutakeol 54 2.3.3. y-Lactones 55

3. S~ 56 4. Acknowledgements 56 5. References 57

Towards Environmentally Friendly Chemical Processes 59 Roger A. Sheldon, Delft University o/Technology

1. Introduction 59 2. The E-Factor and atom efficiency 59 3. The role of catalysis 60 4. Catalytic reduction 62 5. Catalytic oxidation 63 6. Catalytic C-C bond formation 65 7. Catalysis with solid acids and bases 67 8. Catalytic conversions in non-conventional media 69 9. Biocatalysis 72 10. Asymmetric catalysis 73 11. Concluding remarks 75 12. References 76

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Advances in the Industrial Synthesis of Medium to Large Ring Molecules 79 Simon Ellwood, Tom Haines, Quest International

1. Introduction 79 2. Synthesis and macrocyclisation of bifunctional chains 81

2.1. Synthesis of bifunctional chains 81 2.2. Macrocyclisation ofbifiutctional chains 85

3. Macrocycles via ring expansion 88 4. Macrocycles via cyclooligomerisation 91 5. S~ 93 6. References 94

Analysis Technology 97 Alain Chaintreau, Nestle Research Center, Nestec Ltd

1. Introduction 97 2. Sample preparation 97

2.1. Methods based on volatility 98 2.1.1. Distillation 98 2.1.2. Headspace 98

2.2. Extraction methods 100 2.2.1. With a fluid 101 2.2.2. Solid phase extraction (SPE) 101

2.3. Membranes 102 2.3.1. Pervaporation 102 2.3.2. Pertraction and extraction across a membrane 102 2.3.3. Ultrafiltration and nanofiltration 102

2.4. Combined methods 103 2.4.1. Simultaneous distillation-extraction (SDE) 103 2.4.2. Steam distillation-solid phase extraction 103

2.5. Representativeness 103 3. Qua1itative analysis 106

3.1. Separation of volatile constituents 106 3.1.1. Multidimensional gas chromatography (MDGC) 106 3.1.2. Chiral GC columns 106 3.1.3. Preparative capillary GC 107 3.1.4. Profile recognition 107 3.1.5. Derivatisation 107

3.2. Identification of sensory-relevant constituents 107 3.2.1. Mass spectrometry 108

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3.2.2. Isotopic ratio-mass spectrometry 109 3.2.3. Fourier transformed infrared spectroscopy (FTIR) 109 3.2.4. Atomic emission detector (AED) 109 3.2.5. Nuclear magnetic resonance (NMR) 109 3.2.6. GC-olfactometry (GC-O, also called GC-sniffing) 110

3.3. Sensor arrays 111 4. Quantitative analyses 111

4.1. Sample preparation 111 4.1.1. Extraction 112 4.1.2. Headspace 112 4.1.3. Combined methods 113

4.2. Separation and Quantification 114 4.2.1. GC 114 4.2.2. HPLC 114 4.2.3. MS 114 4.2.4. GC-FTIR 114 4.2.5. GC-O 114

5. Data banks 115 5.1. GC 115 5.2. MS 115 5.3. FTIR 115 5.4. NMR. 115 5.5. GC-O 115 5.6. Miscellaneous 116

6. Conclusions 116 7. Bibliography 116

Flavour Matrix Interactions 123 A.J. Taylor, Samworth Flavour Laboratory, University of Nottingham

1. Introduction 123 2. Interactions of volatile flavours with aqueous solutions 126

2.1. Simplest case - equilibrium above aqueous solutions 126 2.2. Non-equilibrium conditions 128

3. Interactions with starch 130 3.1. Starch at low moisture concentration 131 3.2. Other food biopolymers 132

4. Oil-water partition 133 5. Interactions of volatile flavours with proteins 133 6. Encapsulation 134

6.1. Cyclodextrin binding 135

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6.2. 'Glassy matrices' 135 7. Conclusion 135 8. Acknowledgements 135 9. Bibliography 135

Biotransformations in the Flavour Industry 139 RalfG. Berger, Jan A. M de Bont, Gerrit Eggink, M Manuela da Fonseca, Maik Gehrke, Jean-Bernard Gras, Frederik van Keulen, Ulrich Krings, Christian Larroche, David J. Leak, Mariet J. van der Werf. See the chapter for addresses.

1. Summary 139 2. Introduction 140 3. Problems encountered in flavour biotransformation studies 141 4. Advantages of biotransformation 142

4.l. Production of natural flavours 142 4.2. Production of uniform products at a constant productivity 142 4.3. Regio- and stereoselectivity 143 4.4. Environmentally friendly production methods 143 4.5. Production of natural flavours which are not found in appreciable amounts in nature 143

5. Toxicity / solvent tolerance 143 5.1. Compounds in microbial membranes 144 5.2. Solvent-tolerant bacteria 145 5.3. Mechanisms of solvent tolerance 145

6. Genetic engineering: success and perspectives 146 6.l. Present status 146 6.2. Perspective applications of genetic engineering 148

6.2.1. Process improvements by genetic modification of biocatalysts 148 6.2.2. Genetic engineering of natural product catabolic pathways 149 6.2.3. Pathway manipulation 150

7. Process development 150 7.1. Downstreaming options 150

7 .l.1. Pervaporation 151 7.1.2. Supercritical fluid extraction 151 7.1.3. Other options 152

7.2. Equilibrium properties: vapour phase, water solubility, activity coefficient 152

7.2.1. Experimental determination ofVLE data 152

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7.2.1.1. Basis for methods 152 7.2.1.2. Principle of measurement techniques 153 7.2.1.3. Application to terpenes and terpenoids in water 154

7.2.2. Data correlation 154 7.2.2.1. Vapour pressure 154 7.2.2.2. Solubility, activity coefficient 154

7.3. The use of solvents in process development 156 7.3.1. Improved stability 157 7.3.2. Microbial growth in the presence of an inhibitory epoxide 157 7.3.3. Conditions for the maintenance of cell viability 158 7.3.4. Use of the solvent as reservoir 159

7.4. Solid phase adsorption - selective properties in aqueous and organic solution 160

7.4.1. Derivatisation of adsorbant material 160 7.4.1.1. General methods 160 7.4.1.2. Derivatisation procedure 161

7.4.2. Experimental determination of adsorption preference 162 7.4.2.1. Adsorption from the aqueous phase 162 7.4.2.2. Salting-out effect 163 7.4.2.3. Kinetic studies 164 7.4.2.4. Adsorption from organic phase 164

8. Economic considerations 165 9. Acknowledgements 167 10. References 167

Lipid Derived Flavours 171 Wolfgang Fitz, JosefKerler, and Hugo Weenen, Quest International

1. Introduction 171 2. Non-enzymatic lipid oxidation 172

2.1. Autoxidation 172 2.2. Photooxidation 174 2.3. Breakdown of hydroperoxides 175

2.3.1. Acid-catalysed breakdown of hydro peroxides 175 2.3.2. Thermal breakdown of hydro peroxides 176

2.4. Applications 179 2.4.1. Margarine's and spreads 179 2.4.2. Savoury 180 2.4.3. Tobacco 180

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3. Enzymatic lipid oxidation 181 3.1. Lipoxygenase 181

3.1.1. Soybean lipoxygenase 185 3.1.2. C-9 specific lipoxygenase 185

3.2. Hydroperoxide lyase 186 3.3. Applications 186

3.3.1. C6-aldehydes and alcohols 186 3.3.2. Mushroom flavours 187 3.3.3. Various 187

4. Lipids as a source of positive and negative flavours in food 187 4.l. Lipids as precursors of desirable flavours 188

4.1.l. Aldehydes 189 4.l.2. Ketones 193 4.l.3. Alcohols 197 4.1.4. Acids and esters 197 4.l. 5. Lactones 197

4.2. Lipids as precursors of undesirable flavours 203 4.3. Odour thresholds of lipid derived aroma compounds 206

5. References 208

Safety and Legislation of Flavourings 215 Dr. F. Grundschober, I. o.F.I / I.F.R.A.

l. Introduction 215 2. System of regulation 216 3. Definitions 217 4. Labelling 218

4.l. Declaration on the label of flavourings 218 4.2. Declaration on food labels 219

5. Suitable flavouring substances 220 5.1. The GRAS system 220 5.2. The mixed system 221 5.3. The positive list system 223

6. Safety evaluation of flavouring substances 223 6.1. FEXPAN 223 6.2. Council of Europe flavour experts 224 6.3. Joint F AOIWHO expert committee on food additive-JECF A 224

7. Future developments 227 8. References 227

Index 231

PREFACE

This book is designed to give the reader up to date infonnation on some of the more exciting developments that have taken place at the leading edge of fragrance and flavour research.

Chapter one gives the reader a rnpid excursion through the chronological landmarks of fragrance and flavour materials and sets the scene for the remaining nine chapters which cover topics that are at the forefront of modem research. Chapter two looks at the total synthesis of synthetically interesting perfumery naturnl materials. This chapter aims to highlight the creative and elegant chemistry that has been performed by some of the worlds greatest chemists in their quest to synthesise one of the five naturnl products reviewed in the chapter. The chapter fits in with the forward looking theme of the book as it will hopefully inspire other chemists that are interested in synthesising natural products to produce elegant new, or industrially applicable routes to these and other perfumery materials. Chapter three looks at the growing area of interest in asymmetric fragrance materials. The chapter focuses on the use of the metal-BINAP catalytic system for the preparation of fragrance and flavour ingredients. Environmental considerations are now an integrnl and vital part of planning any new industrial chemical process. Chapter four aims to give the reader an insight into the wide-ranging and often readily applicable chemistry that is currently available for the installation of environmentally friendly chemical processes. Our final chapter (chapter five) in the frngrance area concerns the area of chemistry relating to the manufacture and synthesis of macrocyclic molecules. The chapter aims to look at and review the progress of the most recent advances in the industrial synthesis of medium to large ring molecules.

The analysis of flavour and fragrance molecules has always been a hard task due to their often-complex composition in high dilution in a no less complex non-volatile matrix. Chapter six, the first of our flavour orientated chapters looks at the newer methods and at the recent advances in known methods for the analysis of volatiles in the flavour area. Chapter seven looks at the area of flavour matrix interactions, whilst chapter eight concerns itself with biotransformations in relation to the flavour industry. Biotransformations are becoming more frequently a commercially viable option for the preparation of some materials of interest to the flavour and fragrance industry. Chapter nine looks at lipid derived flavours. The chapter brings all of the current literature together and looks not only at the processes involved in producing lipid-derived flavours, but also at the applications of these flavours, whilst our final chapter (ten) looks at the current safety and legislation issues surrounding the flavour area.

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Finally, I must thank Lucy Swift and Kim Yarwood who both helped with the proofreading of some of the chapters. I must also thank all of the authors, firstly, for their excellent manuscripts and secondly, for their patience considering the turmoil that the transition from Thomson Science to Kluwer Academic publishers caused. Finally I would like to thank the publisher, Kluwer Academic for publishing the book.