Application of NMR to Resolve Food Structure, Composition and Quality

Food is a complex system formed by several chemical compounds and physical structures at different organization levels. For food analysis and characterization, it is not only important the study of the chemical composition, which will define the nutrient content, but also the physical distribution of the different compartments and structures that will define the physical properties of food products. Physical properties of food will define the palatability and texture of the food product and thus, the acceptance by the consumers. When talking about Nuclear Magnetic Resonance (NMR) spectroscopy we refer to several techniques that study the interaction of electromagnetic radiation with matter. Nuclear magnetic spectroscopy is the use of the NMR phenomenon to study physical, chemical and biological properties of matter, from the microscopic to the macroscopic. NMR spectroscopy is a very successful and multipurpose technique which is very suitable combined with chemometrics, for the analysis of food products [1]. In this chapter, we will review several NMR techniques that are related to both chemical and physical characterization. Such techniques are 1H High-Resolution Magic Angle Spin (1H HR-MAS), which provides a high resolution chemical spectrum without component extraction [2], relaxometry, which gives information about the water compartmentation, structure and integrity [3], magnetic resonance imaging (MRI) and chemical shift imaging (CSI), which is an efficient tool for the physiological analysis of fruit and vegetables [4]. The following chapter will address, first of all, what needs to be measured on food, as well as several NMR techniques that have been used for the analysis of food products. These techniques are 1H High Resolution Magic Angle Spin (1H HR-MAS), MRI, 1D and 2D relaxometry, relaxometry mapping and chemical shift imaging. We further focus on the explanation of multicomponent analysis and finally offer some remarks about prospects in the field.

Keywords: Chemical properties, Chemometrics, Food structure, Macrostructure, Microstructure, Physical properties, Structure, Texture.