Molecular motions in olive oil from nuclear magnetic relaxation over five orders of magnitude of magnetic field

In this manuscript, we study the complex motions of the individual hydrogen atoms in olive oil, a popular, real-world example of a complex viscous liquid, by measuring the magnetic field-dependence of their relaxation rates. These rates depend on several structural and motional parameters, and are thus relevant for understanding molecular structure and dynamics: the analysis of individual rates can inform on motions occurring on a wide range of timescales (from microseconds to tens of picoseconds) and on their relative weights, providing insights on the different mobility regimes of molecular groups that can move – at least in part – independently, and which are at the basis of their macroscopic properties. We have here combined field-cycling relaxometry measurements performed from 0.01 to 40 MHz using a fast field-cycling relaxometer, with no spectral resolution, and site-specific measurements performed from around 2 to 400 MHz using a newly developed fast sample shuttle system installed on a 600 MHz NMR spectrometer, which allows for polarization and detection at high field. We performed an integrated analysis of these relaxometry measurements. Molecular dynamic simulations are in qualitative agreement with the physico-chemical picture emerging from the data. The same experimental strategy is applicable to all kinds of triglycerides in the liquid state and, more generally, to many complex viscous liquids.