Determination of a molecular fouling model for the micro- and ultrafiltration of whey: A recombination study from single whey proteins to complex mixtures

Since there has been a lack of knowledge concerning the molecular understanding of the specific fouling mechanism during deposit layer structure formation, in this study membrane fouling during the filtration of single whey protein fractions was investigated at various pH and ionic strength. During the filtration of both individual whey proteins and whey protein mixtures, membrane fouling was found to be strongly correlated to repulsive inter-particle forces and pH-dependent protein cross-linking reactions. A disproportionate decrease of the specific fouling resistance from pH 6.4 to pH 7.5 was observed when proteins with a free thiol group were present. At pH 3, α-lactalbumin exists in apo-form, which may cause an increased fouling resistance at acidic pH. Based on the insights gained from this study, membrane fouling during the filtration of whey protein mixtures comprising different native whey proteins in either acid or rennet whey can be explained.