A brief review on the application of NMR relaxation methods in food metabolomics for arabica coffee

Nuclear Magnetic Resonance (NMR) relaxometry has emerged as a complementary tool in food metabolomics to investigate molecular dynamics beyond conventional spectral analysis. In coffee systems, longitudinal (T₁) and transverse (T₂) relaxation times provide insights into molecular movements and interactions relevant to flavor and aroma development during brewing. T₁ relaxation is primarily associated with slower molecular motion and bulk interactions, such as water mobility and lipid matrix organization on longer timescales. In contrast, T₂ relaxation is more sensitive to faster, localized molecular dynamics, including water-solute interactions, molecular confinement, and structural heterogeneity within the coffee matrix. These short-range dynamics are directly involved in the release, diffusion, and perception of volatile and non-volatile compounds, making T₂ relaxation more closely related to aroma intensity and flavor expression during extraction. This review summarizes the principles of NMR relaxation and its applications in various food matrices, with Arabica coffee discussed as a representative complex system. Methodological challenges, inconsistencies in reporting, and limitations in interpretation are highlighted. From a sustainability perspective, NMR relaxometry aligns with the principles of green analytical chemistry by enabling rapid, non-destructive analysis with minimal solvent consumption. Future directions toward standardized and meaningful relaxation-based NMR applications in coffee research are discussed.