J Sci Food Ayric 1996,72,511-512

Book Review

Advanced dairy chemistry-Vol2: Lipids P F Fox Chapman and Hall, London, 1995 f110.00, xiv + 443pp ISBN 0 412 60620 8

The companion volume to this book, Advanced dairy chemistry-Vol 1 : Proteins was reviewed in this journal (68 397-398). The reviewer pointed out that these books are advanced texts and can be regarded as the second edition of ‘Developments in dairy chemistry’. Both are intended as a reference for senior undergraduate and graduate students, researchers and teachers in higher education.

Sixteen contributors have contributed to the 10 chap- ters, which cover the topic of lipids from composition through the influence of nutritional factors, origin of milk globules and the physical chemistry, crys- tallisation, technology aspects of the subject matter. There are two chapters dealing with lipolytic enzymes and lipid oxidation and the final two chapters discuss the nutritional significance of lipids and the role of fat in consumer acceptance of dairy products. The authors are truly international, two from the USA, two from Australia, two from New Zealand, three from the Netherlands, three from Eire the remaining four from Britain.

The fatty acid composition of milk lipids is treated in a very broad sense. Not only bovine but human, rabbit and other non-ruminant herbivores are covered. A goodly number of tables list the acids as well as the distributions of the triacyl glycerol isomers. Future research trends are also discussed. The biosynthesis of milk lipids is well covered and the functions of the various enzymes involved are well discussed; other milk lipids apart from triacyl glycerol derivatives are included. Dietary influence is not neglected and the influence of the season of the weather adequately dis- cussed. It is pointed out, and the reasons indicated, why Canadian milk fat is particularly low in triacyl glycerol derivatives whilst both Australia and New Zealand are relatively low compared with other milks.

The extracellular origin, growth and cytoplasmic transit and secretion of milk lipid globules are thor- oughly treated in the form of an overview. The liter- ature is almost all within the last 25 years. Some clearly reproduced electron micrographs are of considerable help to the reader. The composition of the milk globule

membrane is well covered and the enzymes present dis- cussed. The problem of the organisation of the mem- brane is included in the discussion. In future work, the information on the biological roles of the individual globule membrane commitments will become clearer.

The physical and colloidal aspects of the milk fat globule in cow’s milk are well treated. Foaming and whipping are strongly affected by their properties and they also play an important role in emulsions. The problems of instability are not omitted and interaction energy and cold agglutination are discussed. A consider- able portion of this chapter deals with fat globules in aerated products including ice cream and in water-in-oil emulsions such as butter.

Crystallisation and rheological properties of milk fat are discussed fully, dealing in polymorphism, compound crystals and recrystallisation. Crystal networks and the factors which affect consistency are covered. The pro- cessing of fat spreads is an important topic for butter and margarine makers. A study of the fundamental aspects of emulsions is essential and the effects of ingre- dients in emulsions. In recent years low-fat spreads have increased and there are now a number of studies on ingredient interactions. Emulsion rheology cannot be neglected. An extensive further reading list is given here, in addition to the usual references.

Lipolytic enzymes and hydrolytic rancidity in milk and milk products are discussed initially from the view- point of the individual enzymes and psychrotropic bac- terial lipases are included. The causes of hydrolytic rancidity are dealt with under induced lipolysis, sponta- neous lipolysis and microbial lipolysis. Both beneficial effects of lipolysis and analytical methods are discussed. A table is given on methods for determining lipase activity and how to prevent the problems occurring. Lipid oxidation is a most basic chemical reaction occurring in food and generally results in a deterio- ration in quality. The mechanism, products and factors which affect oxidation of lipids in milk are clearly treated. The function of metals and the use of anti- oxidants are covered. An interesting section on choles- terol oxidation and measurement of lipid oxidation concludes the treatment.

The nutritional significance of lipids is treated in a separate chapter. This covers the lipids in the human body and their functions. This is not restricted to dairy lipids and would in fact be more at home in a general nutritional monograph. The roles of food lipids and the

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roles of vitamins, as well as the importance of coronary heart disease, are discussed. Cancer prevention is also included. So much still requires to be known before the importance of lifestyle and diet can be fully integrated in unequivocal recommendations. The key to good diet is still variety.

In the final chapter, the role of fat in products is dis- cussed and how the consumer views various types of products. Texture and flavour are both important and attitudes often overrule both. The relationship of beliefs and attitudes to food choice is discussed and the meth- odological approaches necessary to explain the product consumer behaviour are listed. It is an interesting and provocative chapter.

Book review

Each chapter has an extensive list of up-to-date refer- ences and there is an enormous amount of information present in a form which can only help in teaching and understanding dairy lipids. The editor, Prof P F Fox, is to be congratulated on gathering such a distinguished collection of authors and in obtaining their contribu- tions from them. The volume concludes with 11 pages of index, although the section headings within each chapter are very helpful.

I Morton