Complexes between linoleate and native or aggregated β-lactoglobulin: Interaction parameters and in vitro cytotoxic effect

The dairy protein beta-lactoglobulin (beta lg) is known to form a complex with fatty acids (FA). Due to industrial processing, beta lg is often in its non-native form in food products, which can modify the FA/beta lg complex properties. We investigated the interaction of bovine beta lg, in selected structural forms (native beta lg, a covalent dimer and as nanoparticles), with linoleate (C18:2). Using fluorescence and Isothermal Titration Calorimetry, linoleate was found to bind beta lg at two different binding sites. Regardless of the structural state of beta lg, association constants remained in the same order of magnitude. However, the stoichiometry increased up to 6-fold for nanoparticles, compared to that of native beta lg. The impact of these structural changes on linoleate uptake in vitro was measured by cytotoxicity assays on Caco-2 cells. The order of cytotoxicity of linoleate was as follows: free > complexed to dimers > complexed to nanoparticles > complexed to native beta lg. Therefore, the in vitro cytotoxicity of linoleate could be modulated by altering the state of beta lg aggregation, which in turn affects its binding capacity to the FA. (C) 2013 Elsevier Ltd. All rights reserved.