Apostolos Spyros is an Assistant Professor of Analytical Chemistry at the University of Crete. He has more than 20 years of hands-on experience in modern magnetic resonance techniques, including high resolution 1D, 2D and heteronuclear NMR, solid state NMR and MRI, and teaches analytical chemistry, spectroscopy and food analysis. During the last 10 years his research has focused on the development of novel analytical NMR methodologies for the characterization of organics, biomolecules, and lipids in complex matrices. He has published original papers and reviews dealing with analytical NMR applications in foods, natural products, biopolymers and organic materials in cultural heritage. Photis Dais is a Professor of Physical Chemistry and director of the NMR laboratory at the University of Crete with over 30 years of experience in NMR spectroscopy with a wide range of applications. During the last decade, he has published 21 research and 7 review articles and book chapters on food analysis and characterization by employing NMR spectroscopy. During the same time period, he has supervised 20 undergraduate diploma theses, 10 MSc theses, and 5 PhD theses, all on food science. He is the reviewer of 22 international journals and member of the editorial board of three journals.

NMR Spectroscopy in Food Analysis

By Apostolos Spyros, Photis Dais

The Royal Society of Chemistry

Copyright © 2013 Apostolos Spyros and Photis Dais
All rights reserved.
ISBN: 978-1-84973-175-1

Contents

Chapter 1 Introduction,
Chapter 2 Theoretical Aspects,
Chapter 3 Instrumentation,
Chapter 4 Sample Preparation,
Chapter 5 Experimental Conditions and Processing,
Chapter 6 Chemometrics in Food Analysis,
Chapter 7 Fats and Oils,
Chapter 8 Wine and Beverages,
Chapter 9 Fruits and Vegetables,
Chapter 10 Milk and Dairy Products,
Chapter 11 Meat,
Subject Index,

CHAPTER 1

Introduction

Nuclear magnetic resonance (NMR) spectroscopy is an effective analytical technique, which has been used systematically in food analysis and authentication in recent years. Its origin is traced back to 1946 when two groups of scientists at Harvard University (Purcell, Torrey and Pound) and at Standford University (Bloch, Hansen, and Packard), working independently, observed proton resonance signals from paraffin wax and water, respectively. For their discovery, Purcell and Bloch were jointly awarded the Nobel Prize in Physics in 1952.

The first application of NMR in food science dates back to 1957 when low-resolution NMR measured moisture in foods. Consistent and widespread application of NMR in food science started in the 1980’s mainly due to deficiencies in instrumentation and the complexity of food matrices. Since then, an explosive publication of research and review articles dealing with NMR applications in food science has appeared in scientific journals and several books. Figure 1.1 shows diagrammatically the explosion of publications in food science after 1988.

Also, numerous oral and written communications have been presented in domestic and international conferences. In particular, an International Conference on Application of Magnetic Resonance in Food Science is held in Europe every two years. This conference started in 1992 and gave the opportunity for scientists worldwide to present new applications of NMR in food science and technology. It is worth mentioning that NMR methods have been approved as official methods by the European Union (e.g. detection of wine fraud). There are several reasons for this development: (a) the increasing sophistication and the user-friendly NMR instrumentation; (b) the increasing need of the food industry to understand innovate its products and processes; and (c) the necessity for the development of new and more effective analytical techniques for the quality control and authentication of foods and thereby the reinforcement of pertinent legislation.

Foods are very complex and highly heterogeneous systems comprising a large number of chemical compounds, the composition of which varies considerably under certain circumstances (e.g. agronomical or slaughter practices, industrial processes, storage, maturation, etc.). To this direction, one-dimensional (1D) liquid or solid-state high-resolution NMR spectroscopy can provide in a single experiment a wealth of structural and quantitative information in the form of the NMR parameters, namely chemical shifts, coupling constants and signal intensities. For the same sample the researcher can choose different nuclei, such as 1H,13C,31P,19F — to mention the most popular nuclei — that allow the study of food samples under different perspectives and to extract the maximum information about its natural or industrial condition. These experiments need no separation of the various food components and no serious sample pre-treatme