Fractionation of soybean proteins with pressurized carbon dioxide as a volatile electrolyte

Fractionation of specific proteins from plant material is a complex and inv olved science, yet pure protein extracts are in high demand by a wide range of food and pharmaceutical industries. In this study carbon dioxide has be en used as a volatile electrolyte to isoelectrically precipitate two major protein constituents of soybean. Carbon dioxide was shown to be effective i n purifying glycinin and beta -conglycinin in a three-step process as 95% a nd 80% concentrated fractions with precipitation yields of 28% and 21%, res pectively. Recycling of the mixed precipitate of the intermediary step enab les complete separation into the concentrated fractions. Fractionation acid ity was precisely controlled by a simple modification of pressure. in addit ion, the occurrence of a pH overshoot was prevented at any point in the fra ctionation vessel, as the pH minimum was defined by its equilibrium relatio nship with carbon dioxide operating pressure. The removal of the glycinin p recipitate was an important factor in the purification procedure. The yield of the individual concentrated glycinin and beta -conglycinin precipitate fractions was a function of carbon dioxide pressure, extract concentration and, to a much lesser extent, temperature. (C) 2001 John Wiley & Sons, Inc.