Book review The Chemistry of Heterocyclic Flavouring and Aroma Compounds. G. Vernin (Ed.) Ellis Horwood Ltd, Chichester, England, 1982. 375 pp, C32.50

The first chapter in this book is concerned with the precursors of heterocyclic aroma compounds but also includes many reaction schemes for aliphatic compounds. Two kinds of precursors are considered: those which occur naturally in foods and others which are produced during processing. Since the author has given examples for a wide range of foods and beverages, including nuts, fruit, vegetables, bread, dairy products and alcoholic and non-alcoholic beverages, it is inevitable that none of these topics is covered in any great depth, but the field is well reviewed and the author includes over 200 references.

The occurrence and organoleptic properties of heterocyclic aroma compounds are covered in Chapter 2, which includes a number of tables, listing the occurrence and odour descriptions of many compounds. The text is roughly divided into three sections, five membered heterocyclics, six or more membered heterocyclics and fused ring systems. The chapter also contains a considerable amount of data and a comprehensive list of references.

Maillard reactions occur in all processed foods, and the mechanism of these reactions together with pyrolysis reactions are the subject of Chapter 3. In addition to many reaction schemes, this chapter also includes a number of tables listing the occurrence of heterocyclic compounds in both foods and model systems.

The next two chapters are devoted to the synthesis of heterocyclic aroma compounds, but with different approaches. Chapter 4 reviews a number of named reactions and provides references to many standard organic textbooks. Chapter 5 describes a novel approach to organic synthesis using a computer to predict the products of Maillard reactions and

model system reactions. This approach, although it can utilize only mechanisms for which the computer is programmed, does ensure that synthetic routes d o not escape the attention of the chemist.

The next two chapters deal with recent techniques for the analysis of heterocyclic compounds in foods. Chapter 6 is essentially concerned with isolation techniques but also includes sensory data for a number of compounds. Identification techniques reviewed include infra-red, ultra-violet and nuclear magnetic resonance, spectroscopy as well as capillary chromatography and GC-MS and LC-MS. Two topics which have not been adequately covered in the text are infra-red spectroscopy and headspace techniques. References might have been given to libraries of infra-spectra and to some standard texts. Headspace techniques are mentioned only briefly, again without adequate references.

Chapter 7 is devoted entirely to mass spectral fragmentation of heterocyclic flavour compounds. This is a vast subject, and it would be impossible to cover such a wide range of compounds and ionization techniques in any detail within one chapter, but sufficient information is given to provide the flavour chemist with a useful introduction into the use of mass spectrometry for the identification of flavour compounds.

The final chapter deals with legislation of flavour, particularly in relation to the use of heterocyclic compounds as flavouring materials. Valuable information is provided in the form of tables of permitted usage and toxicity levels of numerous compounds.

This book succeeds in reviewing a very wide field, covering most aspects of heterocyclic chemistry in relation to food flavour. Inevitably some aspects are not treated in any great depth, but this is well compensated for by the inclusion ofa large number of references. By virtue ofthe number oftopics included in a single volume, this book will be invaluable to the flavour chemist in both industry and research. It will also provide a valuable reference book for students of food science.

D.J.M.

1 Erratum Sillett, C . S. Energy aspects ofcleaning-in-place. Vol. 35, No. 3.

Ju ly 1982. pp. 87-91.

Throughout this paper the unit mJ = millijoule = 0.001 joule should be replaced by MJ = megajoule = 10°joule

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