Phytate, as a minor constituent of soybeans, has been reported to interfere with the dietary mineral absorption of mammals. Commercial soy protein isolate contains 2-3% tightly bound phytate. Practifrom soy protein materials. However, in this reported process, the phytate content was reduced to extremely low levels using commercially feasible processing techniques. The first step of this process was the extraction of water soluble components from soy flakes using routine commercial procedures. In the second step, the extract was adjusted to pH 11.6 at 28 C to insolubilize the phytate. The phytate was removed by centrifugation or vacuum filtration. Neutralization followed the phytate removal. The temperature and pH are critical for phytate removal but also must be carefully controlled to prevent protein degradation. Lysinoalanine was not detected nor was cysteine or other amino acids found to be degraded. The third step of this process was purification of the protein. In this case, the low phytate soy extract was purified by Ultrafiltration until permeate equivalent to 1/2 times the volume of the extract was collected. The phytate and phosphorus contents of the resulting soy protein isolate were 0.1 and 0.2%, respectively, compared to 2.6 and 0.8 for typical commercial soy protein isolate. The PER was significantly better than an acid isolate prepared from the same soy flakes or the commercial soy isolate tested. The retenate obtained after purification by Ultrafiltration was a translucent liquid with a protein content of 5-6%. This protein was in a very soluble form and was stable to heat. © 1979 American Oil Chemists' Society.
