Low-resolution 1H spin-spin relaxation of n-decane/water emulsions stabilized by β-casein

A low-resolution 1H NMR relaxometry study on the dynamics of an n-decane/water emulsion stabilized by β-casein is presented. Spin-spin (transverse) relaxation time constants (T2) were used to assess relative mobilities of emulsion components, by a selective deuteration procedure. Data analysis allowed the emulsion investigated to be described by a heterogeneous collection of dynamically distinct populations. A major population of n-decane molecules presented an average mobility that very nearly approached that of pure solvent, which is compatible with its occurrence in the emulsion continuous microphase. β-Casein molecules displayed a prevalent population with significantly decreased mobility as compared to the free protein in solution, which is in accordance with the protein location at the oil/water interface. Also, a major H2O population with significantly lower average T2 as compared to the pure liquid was detected and has been assigned to interfacial water.