Effects of Surfactants on Wheat Protein Fractionation by Flow Field-Flow Fractionation†

Abstract

The effects of different nonionic (Brij 35, FL-70, Triton X-100, Tween 20 and Tween 80), cationic (CTAB) and anionic (SDS) surfactants in 0.05M acetic acid, at several concentrations, on flow field-flow fractograms of three wheat gluten fractions were assessed. Alcohol soluble gliadins, acetic acid soluble glutenins and sonicated acetic acid insoluble glutenin fractions all showed optimum resolution and reproducibility with FL-70, Brij 35 or Triton X-100. Fl-70 proved superior compared to the other two surfactants due to its lower tendency to foam, making buffer preparation much easier. Fractograms obtained in the presence of low concentration of other nonionic surfactants (Tween 20 and 80) and the cationic surfactant, CTAB, gave similar fractograms but resolution was inferior. At higher concentration, above the critical micelle limit, CTAB gave poor resolution and reproducibility. Low concentrations of SDS caused protein precipitation. At a higher concentration of SDS, also above the critical micelle concentration, reproducibility was also a problem. However, results indicated that SDS was able to release lower molecular weight proteins from the larger polymeric insoluble gluten fraction which remained bound with nonionic detergents. †Contribution No 750 of the Canadian Grain Commission, Grain Research Laboratory, 1404–303 Main St., Winnipeg, MB R3C 3G8.