EMULSIFYING PROPERTIES OF PURE AND MIXED ALPHA-S1-CASEIN AND BETA-CASEIN FRACTIONS - EFFECTS OF CHEMICAL GLYCOSYLATION

Alpha-s1- and beta-caseins were prepared from whole casein by batchwise ion-exchange chromatography before being chemically galactosylated. Solubility of these pure fractions was found to be minimal around the isoelectric point (pH 4-5). The glycosylation and the increase of the ionic strength improved the solubility in the range of isoelectric pH and had a small effect on both sides of this pH. Glycosylation had little effect on the emulsifying index. Emulsions made from alpha-s1-caseins do not have the same stability as emulsions from beta-caseins. Nevertheless, glycosylation does not influence the behavior of each fraction as far as emulsion stability is concerned. Binary mixtures of alpha-s1- and beta-caseins had a lower emulsifying activity index than the arithmetical calculated value. Adding galactosylated beta-casein to those binary mixtures improved the emulsifying activity of the resulting ternary mixtures. Then, glycosylation would limit the intermolecular interactions rather than improve the properties of the monomeric casein fractions.