Carbohydrate and mineral removal during the production of low-phytate soy protein isolate by combined electroacidification and high shear tangential flow ultrafiltration.

In this work, soy protein isolates were produced by a combination of electroacidification and high shear tangential flow hollow fiber ultrafiltration with a 100 kDa membrane under constant pressure. The filtration performance was evaluated by comparing the filtration time and the final product composition for an electroacidified (pH 6) and a non-electroacidified (pH 9) soy protein extract. The removal of carbohydrates during the filtration was always consistent with the theoretical predictions (based on free permeability assumption) for both the electroacidified and the non-electroacidified feeds. A higher removal of calcium, magnesium, and phytic acid was achieved during the filtration of the electroacidified feed compared to the non-electroacidified feed. However, the electroacidification pretreatment had a negative impact on the permeate flux and resulted in more significant membrane fouling with correspondingly longer filtration times. A discontinuous diafiltration enhanced the removal of carbohydrates and minerals, thus yielding a product with higher protein content but was unable to improve the permeate flux for the electroacidified feed.