The liquid structure of some food aromas: Joint X-ray diffraction, all-atom molecular dynamics and reverse Monte Carlo investigations of dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide

Following synchrotron X-ray diffraction measurements on liquid dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide, all-atom molecular dynamics (MD) simulations were carried out for these materials which are known widely used food aromas. The X-ray weighted structure factor calculated from the MD particle configurations was in reasonably good agreement with the experimental data for each liquid. For refining the structure, series of Reverse Monte Carlo (RMC) simulations using various combinations of the experimental structure factor. MD-based partial radial distribution functions, as well as constraints on cosine distribution of bond angles were carried out. The best representation of the structure could be achieved by the simultaneous application of all the above constraints, thus providing an MD-aided RMC structural model of the three liquids. The largest inconsistency between MD and the experimental structure factor showed up in terms of the S-H partial radial distribution function for dimethyl sulfide and disulfide. The coherency between MD results and the experimental structure factor increased with the number of sulfur atoms in the molecule. It is shown that a great deal of information on the intramolecular structure is contained in the X-ray weighted structure factor, whereas intermolecular correlations are represented to a somewhat lesser extent. (C) 2012 Elsevier B.V. All rights reserved.