Effect of different denaturating methods on lipid-protein complex formation

To investigate the effect of denaturation of protein on lipid-protein complex formation in soybeans, different denaturing agents including urea, ethanol, autoclaving, and extreme pH treatment were used. Protein was denatured either in the presence of the oxidized crude soybean oil (MOx OD), or before it was added to the crude oxidized oil (DMOxO). Nitrogen solubility index and in vitro digestibility of the proteins were used to investigate the formation of the lipid-protein complexes. The meal resulting after the denaturation treatment was compared to untreated soybean meal. All treatments resulted in very highly significant differences (P > 0.001) in the studied parameters when compared to untreated meal. Results proved that denaturation of protein in the presence of oxidized oil caused more lipid-protein complex formation than denaturation of the protein prior to the addition to the oxidized oil. Among the denaturing agents examined, urea caused the highest lipid-protein complex as indicated by the in vitro digestibility and nitrogen solubility of the protein. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.