Beyond Moisture Content: Time-Domain NMR for Quantifying Molecular Mobility, Water Accessibility and Food Function.

Moisture content is among the most routinely measured properties of foods, yet water quantity alone does not determine processing behavior, stability, texture, fluid release or sensory function. In heterogeneous food matrices, water occupies environments differing in molecular restriction, compartmentalization, exchange, connectivity and translational mobility. Time-domain nuclear magnetic resonance (TD-NMR) provides a rapid and non-destructive means of interrogating these properties through proton signal intensity, longitudinal and transverse relaxation, relaxation-time distributions, self-diffusion and multidimensional correlation measurements. This review develops a framework extending food-water analysis from quantity to molecular state, mobility, translational accessibility and function. Particular emphasis is placed on distinguishing local molecular environments reflected by relaxation from longer-range molecular displacement characterized by diffusion. Applications in meat, plant-based foods, dairy systems, cereals, gels, frozen and dried foods, and edible oils illustrate how TD-NMR descriptors can be connected with water holding, texture, juiciness, processing behavior, oxidation and shelf life. Integration with structural imaging, mechanical measurements, chemometrics and machine learning further positions TD-NMR as a molecular-state sensing platform for predictive food analysis, product design and intelligent manufacturing.