Fractionation of wheat proteins by counter-current distribution using aqueous two-phase systems containing propionic acid

Wheat proteins, soluble in diluted acid (glutenins), have been fractionated by counter-current distribution (CCD) using an aqueous two-phase system. The phase system is based on poly(ethylene glycol) and dextran but contains also 1% propionic acid and 6 mM magnesium sulfate. Approximately half of the bulk proteins partitioned to the upper phase while starch and other particles were recovered only into the lower phase. Whole wheat flour could be applied as sample for the CCD and 57 transfers were carried out. Starch and insoluble proteins remained stationary, while proteins followed the mobile phase to various degrees giving rise to a distribution pattern. The CCD pattern of the proteins showed distinct differences when various kinds of wheat flour were analysed. The patterns indicate that at least six subpopulations of proteins can be obtained by using two-phase extraction.