Contamination of food by fluorinated surfactants – Distribution in emulsions and impact on the interfacial protein behaviour

Perfluorooctanesulphonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the final products of degradation of numerous fluorochemicals, intensively used in industry. Due to their high stability and low level of biodegradability, they remain in the environment. Their occurrence in milk constitutes one of the numerous initial steps of contamination of many manufactured food products. We contributed to the understanding of the food contamination in analysing the distribution of PFOS and PFOA in food model emulsions. Emulsions stabilised by whey protein isolates were prepared from either contaminated aqueous phase or contaminated sunflower seed oil phase and homogenised at high pressures. Aqueous and creamed phases of emulsions were separated to evaluate the distribution of PFOS and PFOA between these two phases using a combination of liquid chromatography and mass spectrometry. PFOS and PFOA, initially present in water, migrate in the creamed phase due to their bindings with proteins that cover the oil–water interface of oil droplets. PFOS may also be present at interfaces due to its hydrophobicity. PFOS and PFOA bound to proteins moreover modified the interfacial behaviour of proteins at model air–water interfaces in proportions depending on the concentration and the head group of the perfluorinated surfactants.