SAMPLE PREPARATION FOR SELECTIVE AND SENSITIVE DETECTION OF SOYA PROTEINS IN DAIRY-PRODUCTS WITH CHROMATOGRAPHIC AND ELECTROPHORETIC TECHNIQUES

Soya proteins are insoluble in a tetraborate-EDTA buffer, which thus a llows removal of soluble caseins from samples. This selective treatmen t in combination with gel-permeation chromatography achieved a detecti on limit for mass fraction of soya protein in total protein of melted cheese of 6 g/kg. Combination with sodium dodecyl sulfate-polyacrylami de gel electrophoresis achieved a detection limit of 0.6 g/kg, except with enzyme-treated soya proteins. Isoelectric focusing was suitable f or characterizing soya proteins. In combination with the selective sam ple treatment, it achieved a detection limit of 30 g/kg.