Effect of Temperature on the Separation of Soybean 11 S and 7 S Protein Fractions during Bipolar Membrane Electroacidification

The purpose of this study was to evaluate the effect of temperature (10 and 27 °C) on the efficiency of bipolar membrane electroacidification (BMEA) to fractionate soybean proteins. BMEA is a technology derived from electrodialysis, based on the isoelectric precipitation of proteins. It appears that temperature has a significant effect on the selective precipitation of the soybean protein fractions, mainly 11 S and 7 S, during BMEA. At 27 °C, the precipitation profile of the four protein fractions is situated in a pH range from 6.6 to 4.4, with no possibility of separating any of theses fractions. However, at 10 °C, the 11 S globulin precipitates at a higher pH than at 27 °C, pH 6.7 vs 5.9, allowing the fractionation of 11 S from the other fractions. Using electroacidification it is possible to obtain a precipitate solution enriched in the 11 S fraction (71.8% of 11 S and 10.8% of 7 S) and a supernatant solution enriched in the 7 S fraction (46.6% of 7 Sand 4.6% of 11 S).