Portable NMR in food analysis

Abstract

Low-field 1 H NMR relaxometry is an important tool used to investigate on the most abundant components of intact foodstuffs based on relaxation parameters and amplitude of the NMR signals. In particular, information on water compartments, diffusion and movement can be obtained by detecting proton signals prevalently ascribable to H 2 O contained in foodstuffs. The main advantage of this technique is that it does not require any pretreatment of the sample and once developed, standard protocols based on rapid measurements can be easily transferred to quality control applications. An actual breakthrough for the low-field NMR application to food science has certainly been the development of unilateral NMR sensors. These devices present an attractive option for non-invasive assessment of compositional and microstructure of food materials. They are portable and allow easy sample access, which makes them attractive for quality control in industrial environments and directly on sealed packaged foods. A price to pay is the inhomogeneity of the magnetic field, which compromises the sensitivity of these devices. However, recent developments in unilateral magnets design offer larger sensitive volume, higher sensitivity and shorter dead times. In this brief review, we highlight the different uses of unilateral NMR devices in food analysis.

Nuclear Magnetic Resonance (NMR) Spectroscopy in Food Science: A Comprehensive Review

“…A descriptive summary of the most essential NMR concepts that may not be widely recognized by the majority of food scientists, will be provided as well. The most common categories of current NMR analyses of foods are relaxometry (Capitani et al, ; Tavares, ), where differences in the magnetic relaxation of food components are investigated; diffusometry (Mariette, ), where the translational diffusion of molecules is measured; imaging (Ablett, ; Hills, ); and high‐resolution NMR spectroscopy (Belton et al., ; Laghi, Picone, & Capozzi, ; Mannina, Sobolev, & Viel, ; Spyros & Dais, ). In this article, we will focus on high‐resolution NMR applications, although selected application examples from other categories, such as diffusion, will be mentioned as modern high‐resolution NMR instruments are capable of running such experiments if equipped with the appropriate hardware.…”

Potential uses of LF‐NMR and MRI in the study of water dynamics and quality measurement of fruits and vegetables

“…Such spatial details enable the examination of temperature and mass movement in foods and organic materials amid dynamic processes like freezing, thermal dehydration, heating, and preservation (Cikrikci & Oztop, ; Tao & Ngadi, ; Wang et al, ). Technical improvement of equipment and pulse sequences have led to an ever‐increasing number of approved applications, for example, water, oil, fat, and bead size assessment (Capitani, Sobolev, Tullio, Mannina, & Proietti, ). Both LF‐NMR and MRI are able to characterize the water status and distribution in a fast and nondestructive manner.…”

Non-Destructive Quantification of Lipid and Water in Fresh Tuna Meat by a Single-Sided Nuclear Magnetic Resonance Scanner

“…Such measurement systems of the lipid content are also needed for the quality control of aquatic food products at factories (Marcone et al, 2013;Tao and Ngadi, 2018). One such measurement system is a low-field time-domain (non-imaging) proton nuclear magnetic resonance (NMR) surface scanner using single-sided permanent magnets (Blümich et al, 2008;Blümich and Singh, 2018;Capitani et al, 2017;Casanova et al, 2011;Erikson et al, 2012). NMR surface scanners allow the water and lipid contents to be quantified separately by taking advantage of the difference between the proton spin-spin relaxation times (T2 values) of the water molecules in the muscle and the lipid molecules.…”