Applications of NMR to Food Analysis

Relative to most other techniques discussed in this book, NMR has found a limited number of niche applications in food analysis. For example, the determination of oils is seeds (or fat in chocolate ), based upon low resolution, solid phase NMR is well used in quality control laboratories. Actually, most apphcations that found their way in food analysis are methods based upon the differences in relaxation times of various molecules e.g. free water molecules versus bound water molecules). Consequently, for the purpose of this particular chapter, we shall discuss only two specific applications of NMR to food analysis. These examples were chosen solely to demonstrate the broad range of applications that NMR can cover and the reader is advised that the mere fact that they were selected here should not be interpreted as a judgement of their value over other related references. 

Panax spp., especially Panax ginseng, are purported to possess various health benefit qualities. In oriental countries it has been used as a traditional panacea for numerous health disorders for several centuries. Saponins are generally recognised as the main effective components of ginseng. Because of their close similarities in terms of structure they offer a real challenge to the analytical chemist in terms of separation. Furthermore, the relative complexity of their structures makes them perfect candidates for in-depth structural characterisation work by NMR. 

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As per most chapters in this book, we include a short hst (Table 2) of selected applications of NMR to food analysis. It will be obvious to those involved in daily use of NMR that these apphcations are by no means representative of the range of appHcability of NMR to food science, rather they were selected for their practicality and their state of readiness of being implemented into daily food analysis activities. 

Principles and applications of NMR to food analysis Multidimensional detection methods for separations and their 1997 (19)... 

High-resolution applications of NMR in food science have been reviewed.26 Since the appearance of this review in 1984, the use of 2D NMR techniques has become commonplace, greatly increasing the power of NMR as a method for structural analysis of complex natural products, including many minor food components. In this section, however, attention will be given to quantitative rather than structural applications of high-resolution NMR. 

Aman, R. et al.. Application of HPLC coupled with DAD, APcI-MS and NMR to the analysis of lutein and zeaxanthin stereoisomers in thermally processed vegetables. Food Chem., 92 753, 2005. 

NMR is an incredibly versatile tool that can be used for a wide array of applications, including determination of molecular structure, monitoring of molecular dynamics, chemical analysis, and imaging. NMR has found broad application in the food science and food processing areas (Belton et al., 1993, 1995, 1999 Colquhoun and Goodfellow, 1994 Eads, 1999 Gil et al., 1996 Hills, 1998 O Brien, 1992 Schmidt et al., 1996 Webb et al., 1995, 2001). The ability of NMR to quantify food properties and their spatiotemporal variation in a nondestructive, noninvasive manner is especially useful. In turn, these properties can then be related to the safety, stability, and quality of a food (Eads, 1999). Because food materials are transparent to the radio frequency electromagnetic radiation required in an NMR experiment, NMR can be used to probe virtually any type of food sample, from liquids, such as beverages, oils, and broth, to semisolids, such as cheese, mayonnaise, and bread, to solids, such as flour, powdered drink mixes, and potato chips. 

The explosive advancements in NMR technology in recent years have dramatically expanded the avenues and techniques available. NMR techniques for the study of food range from in-line/on-line oil and water analysis, to characterization and authentification of foods and beverages, water relations in foods and biological tissues, mobility of water in food and to probing microstructure of food. The applications of NMR techniques in food research were recently reviewed [2,3]. 

S. Rezzi, C. GuiUou, F. Reniero, V.M. Holland, S. Ghelli (2004) Natural abundance H-NMR spectroscopy. Application to food analysis. In P.A. de Groot (ed.), Handbook of Stable Isotope Analytical Techniques, Vol. I, Elsevier B.V, Amsterdam, pp. 103-121... 

The second part of the book—Chapters 9-12— presents some selected applications of chemometrics to different topics of interest in the field of food authentication and control. Chapter 9 deals with the application of chemometric methods to the analysis of hyperspectral images, that is, of those images where a complete spectrum is recorded at each of the pixels. After a description of the peculiar characteristics of images as data, a detailed discussion on the use of exploratory data analytical tools, calibration and classification methods is presented. The aim of Chapter 10 is to present an overview of the role of chemometrics in food traceability, starting from the characterisation of soils up to the classification and authentication of the final product. The discussion is accompanied by examples taken from the different ambits where chemometrics can be used for tracing and authenticating foodstuffs. Chapter 11 introduces NMR-based metabolomics as a potentially useful tool for food quality control. After a description of the bases of the metabolomics approach, examples of its application for authentication, identification of adulterations, control of the safety of use, and processing are presented and discussed. Finally, Chapter 12 introduces the concept of interval methods in chemometrics, both for data pretreatment and data analysis. The topics... 

In this chapter, we report the NMR-based metabolomic approach in food analysis and display its more instructive applications in quality control in order to illustrate the set of problems related to peculiar data source, the potentiality, and the development features of main interest for chemometricians in this field. Therefore, to overview the different MS-based strategies applied to food analysis, we address the reader to the most recent comprehensive reviews [5,7]. 

NMR spectroscopy is one of the most widely used analytical tools for the study of molecular structure and dynamics. Spin relaxation and diffusion have been used to characterize protein dynamics [1, 2], polymer systems[3, 4], porous media [5-8], and heterogeneous fluids such as crude oils [9-12]. There has been a growing body of work to extend NMR to other areas of applications, such as material science [13] and the petroleum industry [11, 14—16]. NMR and MRI have been used extensively for research in food science and in production quality control [17-20]. For example, NMR is used to determine moisture content and solid fat fraction [20]. Multi-component analysis techniques, such as chemometrics as used by Brown et al. [21], are often employed to distinguish the components, e.g., oil and water. 

There are many examples in the literature for applications of LC-NMR in the pharmaceutical industry. In the area of natural products, LC-NMR has been applied to screen plant constituents from crude extracts [54,57,67,68] and to analyze plant and marine alkaloids [69-72], flavonoids [73], sesquiterpene lactones [74,75], saponins [58,76], vitamin E homologues [77], and antifungal and bacterial constituents [56,78,79] as examples. In the field of drug metabolism, LC-NMR has been extensively applied for the identihcation of metabolites [42, 80-88] and even polar [89] or unstable metabolites [43]. And hnally, LC-NMR has been used for areas such degradation products [90-93], drug impurities [94-102], drug discovery [103,104], and food analysis [105-107]. 

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