NMR applications in food research

Editorial The realization about 50 years ago that nuclei within molecules could be used to report non-destructively on their environment has led to many possible applications in different disciplines. The discovery that signals from many nuclei in molecules (up to the size of small proteins using modem instruments) could be resolved into spectra gave birth to modem nuclear magnetic resonance (NMR) spectroscopy and related techniques such as NMR imaging. The pace of developments in NMR has been accelerating since the early 1970s, both at the basic research level and in the field of applications; the significance of some such developments was acknowledged last year in the award of a Nobel Prize to Dr Richard Ernst for his work in developing Fourier transform NMR techniques. Before the work of Ernst and co-workers, NMR experiments were limited by the continuous-wave instrumentation available at the time, which involved slowly scanning either the magnetic field at constant frequency or, more usually, scanning the frequency at constant magnetic field. The introduction of Fourier transform NMR instruments made possible more rapid signal accumulation times and has facilitated the development of computerized signal processing techniques. The field of high-resolution NMR has also benefited from the introduction of superconducting magnets and more homogeneous magnetic fields. Nevertheless, despite the introduction of Fourier transform techniques and the growing complexity of instrumentation, NMR spectroscopy is a low-sensitivity technique compared with other forms of spectroscopy and many biochemical techniques. This limits the usefulness of NMR as an analytical tool unless the analyte is present in relatively high concentrations. However, NMR makes up for this deficiency in other ways. The specificity of the technique is such that a wealth of information can be obtained from a single NMR experiment; for example, structural data on a complex molecule or information on the mobility of water in a food system. In addition, NMR techniques are non-destructive and non-invasive. A more recently exploited advantage of NMR is the ability to produce spatially resolved spectra and the use of selective saturation techniques coupled with pulsed-field gradients to produce two- and threedimensional images of biological samples. Not surprisingly, the applicability of NMR methods to food research varies with the application in mind. Low-resolution pulsed NMR instruments, such as the Bruker 'Minispec', have been used in the food industry for many years for fat analysis and, in a few applications, for determining moisture content. However, new applications of both low- and high-resolution NMR techniques have been the subject of intense study by food scientists over the past few years. It is possible that some of the new applications may eventually be adapted for in-line/on-line food analysis. Already, trials of such techniques have been conducted in food processing environments. This special double issue of Trends in Food Science & Technology examines a selection of NMR applications in food and nutrition research.

Trends in Food Science & Technology August/September 1992 [Vol. 3J

NMR applications in food research The issue is loosely divided into a number of sections that explore the theory and applications of nuclear magnetic resonance. Two introductory articles are included to introduce the non-specialist to the general principles of NMR ('Introduction to NMR', by Marcus A. Hemminga) and NMR imaging ('Introduction to NMR imaging', by A. Haase). Following the general introduction, two articles examine the applications of low-resolution pulsed NMR in the analysis of fats and oil seeds ('Determination of solid/liquid ratios of fats and oils by low-resolution pulsed NMR', by M.e.M. Gribnau, and 'Applications of low-resolution pulsed NMR to the determination of oil and moisture in oilseeds', by Prem N. Gambhir). High-resolution NMR techniques receive attention in several articles throughout the issue ('Applications of NMR to the characterization and authentication of foods and beverages', by Claude Guillou, Gerald Remaud and Gerard G. Martin; 'Rationale for using NMR to study water relations in foods and biological tissues', by Herman J.e. Berendsen; 'Perspective on the applications of NMR in nutrition', by Alan J. Fischman and Ronald G. Tompkins; 'High-resolution solid-state NMR of food materials', by Michael J. Gidley; 'Applications of 31p NMR in the study of microbial metabolism', by Klaas Nicolay; 'Applications of NMR in sensory science', by Terri Robertson, Shelly Schmidt and Barbara Klein; and 'Applications of NMR spectroscopy in meat research', by Christian Beauvallet and Jean-Pierre Renou). Three articles specifically examine applications of the technique of NMR imaging in food research ('Measurements of moisture diffusion in foods using pulsed field gradient NMR', by Hisahiko Watanabe and Mika Fukuoka; 'Measurement of fat crystallization using NMR imaging and spectroscopy', by e. Simoneau, MJ. McCarthy, D.S. Reid and J.B. German; and 'Application of NMR imaging to the study of velocity profiles during extrusion processing', by Kathryn L. McCarthy, Robert J. Kauten and Cynthia K. Agemura). The issue concludes with an overview article that summarizes the major NMR applications in food research (,Overview of NMR applications in food science', by Steve Ablett). Finally, a glossary is provided at the end of the review section to assist readers who may be unfamiliar with some of the terminology used in the issue. Clearly, there is insufficient scope in a journal such as this to enable coverage of every possible application of NMR techniques in food science and nutrition. Nevertheless, I hope the issue has succeeded in its objective of providing a flavour of what might be possible using NMR techniques. The field of structural analysis using NMR has been omitted since information on this subject is readily accessible in the chemical literature. Similarly, an examination of the purely analytical applications of NMR (e.g. determination of organic acids in wine) has been omitted because such applications are,

©1992, Elsevier Science Publishers Ltd, (UK)

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as yet, relatively few, and considerable development is required. For further information on NMR applications in food science, the reader is referred to a number of recent texts l - 3 • In addition, instrument manufacturers (e.g. Bruker, Hitachi and Oxford Instruments) can usually provide helpful advice on specific applications.

Last issue as Editor Alas, this is my last issue as Editor of Trends in Food Science & Technology. I am returning to University life to resume a research and teaching career in food toxicology. The past 2!1 years have provided me with a wonderful perspective on food science and have served as a reminder that foods and food systems can be the most exciting subjects for scientific study. I have been assisted during my tenure as Editor by a highly professional science publishing team. In particular, lowe a debt of gratitude to Beverley White, Assistant Editor, and Christine Oliver, Editorial Secretary, for their help in launching this journal and contributing to its development. Publications such as Trends in Food Science & Technology are very much

products of effective team work and this journal also owes its existence to publishing professionals such as Judith Bastin, DTP Manager; Nigel Hynes, Graphics Designer; Susan Gatell, Marketing Manager and David Bousfield, Publisher. Finally, the magic ingredients are good science, and the scientists that contribute to such science and who maintain its integrity. I am grateful to our many contributors and especially to the referees and Editorial Board for their guidance and support. The job of monitoring the new trends will, I have no doubt, be continued ably by my colleague, Gillian Griffith, the newly appointed Editor.

John O'Brien References 1 2 3

Finley, J.w., Schmidt, s.J. and serriani, A.5., eds (1990) NMR Applications in Biopolymers, Plenum Press levine, H. and Slade, l., eds (1991) Water Relationships in Foods, Plenum Press Popov, A.1. and Halienga, K., eds (1991) Modern NMR Techniques and their Application in Chemistry, Marcel Dekker

Editorial Policy Trends in Food Science & Technology is a news and reviews journal that enables food scientists to keep abreast of recent developments in all areas of the field. Occupying a niche between primary research journals and comprehensive review journals, it is not a vehicle for the publication of original results or methods. There is a strong emphasis on cross-disciplinary communication and articles are invited to improve understanding of those areas that most need to be highlighted or clarified. In common with other journals in the Trends series, such as Trends in Biochemical Sciences, Trends in Biotechnology and Trends in Pharmacological Sciences, articles for Trends in Food Science & Technology are prepared to strict standards to ensure a high degree of clarity, scientific accuracy and readability. The varied nature of articles, together with the rapid production cycle of the journal, ensures the minimum of delay in the communication of new developments and ideas. Sections of the journal are designed to address specific issues as follows:

Reviews assimilate the recent developments in specific areas of food research. Because of the limited size of articles (usually less than six pages), the scope of such reviews is more restricted than those in comprehensive review journals or books and they focus either on the latest developments (where a comprehensive review would not be justified) or on specific advances in a cognate field. Viewpoints are invited from expert authors, whose.opinions and observations are offered on contentious issues concerning food science, nutrition and food safety. Feature articles are similar in style to Reviews, but are of broader appeal to the food-science community. Current Awareness articles address immediate developments and current issues in food and nutrition research. Such articles are prepared rapidly in response to current information needs. The Book Reviews section provides analytical reviews of recently published books in food science and nutrition. Authors of book reviews are encouraged to consider the contribution of the book in the context of recent developments in the field, and the use of literature references is encouraged.

Trends in Food Science & Technology features regular Conference Reports, which describe the important points addressed by food science conferences worldwide.

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Trends in Food Science & Technology August/September 1992 [Vol. 3]