Noninvasive analyses of food products using low-field time-domain NMR: A review of relaxometry methods

In the last two decades, several noninvasive physical methods based on the interactions of electromagnetic radiation with matter have been developed to evaluate the food quality. Some of these methods uses ionizing radiation or radiation that strongly interacts with chemical compound limiting the analysis to the food surface. Nuclear magnetic resonance (NMR) is based on radiofrequency radiation, so it does not use ionizing radiation and is not strongly attenuated by food or package composition; therefore, it can be used in noninvasive analysis of intact and packaged foods. Although high-resolution NMR spectroscopy and imaging have been used in food analysis, they are usually based on expensive and bulky instruments that limit their practical application. Therefore, most noninvasive NMR-based analyses of intact food have been performed using low-cost, low-field, time-domain NMR instruments (TD-NMR). Instrumental requirements, pulse sequences, applications and limitation of TD-NMR in noninvasive analysis of fresh and industrialized food products will be reviewed. (author)