Capture modes evaluation of four flavor constituents in β-lactoglobulin by high-resolution mass spectrometry and molecular dynamics simulation approaches

Flavor retention and consumer receptivity of goat milk are strongly influenced by the interaction between flavor constituents and proteins. Few previous works suggested the impact of interactions between beta-lactoglobulin (beta-LG) and flavor constituents in goat milk on the release of volatile compounds. In present research, binding of beta-lactoglobulin with four model flavor constituents, octanoic acid (OA), 4-methyloctanoic acid (MCA), 2-tridecanone (TO) and tert-butanol (TB) was deciphered. UHPLC-Q-Orbitrap high-resolution mass spectrometry results identified that all flavor molecules bound to beta-lactoglobulin in the 1:1 stoichiometric ratio. Docking analysis of the lowest binding energy indicated that the strongest binding relationships between beta-LG and MCA/OA/TB/TO were expected to be beta-LG/TO > beta-LG/MCA > beta-LG/OA > beta-LG/TB, which were spontaneous. Via molecular dynamic simulations, TO was located at hydrophobic cavity of beta-barrel causing beta-LG structure to further curl. The spatial direction of MCA began to gradually approach outer surface near Trp19-Arg124. OA was located in entrance of the hydrophobic core of each beta-barrel. TB remained relatively stable at surface hydrophobic sac in the groove between beta-barrel and a-helix. The effect of beta-LG conformation was also evaluated by fluorescence spectroscopy, which was same to the molecular dynamics simulation. Present study may help to better understand the interaction mechanism of beta-LG and flavor constituents and evaluate the ability of flavor compounds having a broad array of different functional groups to react with beta-LG, which provided theoretical basis for quality maintenance of goat milk.