Combination of Ultrafiltration/Diafiltration and Ammonium Sulfate Precipitation for the Purification of 11S and 7S Pea Globulin Fractions

The efficiency of ultrafiltration/diafiltration (UF/DF) combined with selective ammonium sulfate precipitation was evaluated for the recovery of purified 11S and 7S pea globulin fractions. Three UF membranes (30, 100, and 300 kDa) were tested for the fractionation of pea globulins from albumins during pea protein isolate (PPI) production. PPIs were compared to pea protein concentrates, and yields and purities were calculated after ammonium sulfate precipitation. Results showed that UF/DF had no impact on the pea protein profile, purity, and 11S legumin recovery yield. However, the yield of 7S fractions generated from UF/DF-produced PPI was improved. The 11S and 7S fractions had free sulfhydryl group contents of 2.35 and 1.02 μmol/g of proteins and disulfide bond contents of 22.65 and 4.87 μmol/g of proteins, respectively. The temperature of denaturation was 87.15 °C for 11S legumin and 79.07 °C for 7S vicilin. Consequently, PPI production by UF/DF is required prior to ammonium sulfate precipitation to maximize the 7S vicilin yield.