Quality control of agricultural products using magnetic resonance sensors

ABSTRACT Nuclear magnetic resonance (NMR) is a spectroscopy technique widely used by chemists and physicists to determine the chemical structure of molecules that was adapted to generate imaging, known as nuclear magnetic resonance imaging (MRI), which is widely used in medical diagnosis. The importance of NMR in chemistry, physics, medicine, materials, and agriculture has been recognized with several Nobel Prizes in Physics, 1952, Chemistry, 1991 and 2002, and Medicine in 2003. Therefore, NMR can be applied to obtain: i) imaging of the human body, animal and materials; ii) high-resolution spectra to obtain structural and dynamical information of chemicals, materials etc.; and iii) quantitative and qualitative information of chemical composition of products such as food and agricultural products, using low-resolution relaxometry. High-resolution NMR and MRI have been applied in agri-food products, mostly as a research tool as they typically rely on expensive and bulk instruments, which restrict their uses in routine applications. The NMR sensors that have been more frequently used in agri-food products are based on low-resolution or low-field or time-domain NMR (TD-NMR) instruments. These low-cost instruments have been used for qualitative and quantitative analysis of agri-food products such as intact seeds and grains, intact fruits, meat, oils, and processed foods. In this paper, an overview of the NMR techniques and its main instrumentation aspects are presented, and some applications of TD-NMR and MRI in the non-invasive analysis of food, seeds, and others agricultural products are discussed. RESUMO A ressonância magnética nuclear (RMN) é uma técnica de espectroscopia amplamente utilizada pelos químicos e físicos para determinar a estrutura química de moléculas que foi adaptada para gerar imagens, conhecidas como tomografia por imagem de ressonância magnética nuclear (IRM), amplamente utilizada em diagnóstico médico. A importância da RMN na química, física, medicina, materiais e agricultura tem sido reconhecida por vários Prémios Nobel de Física, 1952, Química, 1991 e 2002, e Medicina em 2003. Portanto, a RMN pode ser aplicada para obter: i) imagens do corpo humano, animais e materiais; ii) espectros de alta resolução para obtenção de informações estruturais e dinâmicas de produtos químicos, materiais etc.; e iii) obter informações quantitativas e qualitativas da composição química de alimentos, produtos agrícolas, utilizando relaxometria de baixa resol