Improvement of nutritional quality of soybean meal by Fe(II)-assisted acetic acid treatment.

We investigated the effect of Fe(II)-assisted acetic acid treatment on improvement of nutrition quality of soybean meal (SBM) by degrading antinutritional factors (ANFs) and maintaining initial nutrition quality. Fe(II)-assistance reduced trypsin inhibitor (TI) content significantly from 5.20 to 0.86 mg/g, and allergenic proteins were completely degraded at 55 °C, due to changes in the conformation of soybean protein isolate (SPI) that renders proteins more prone to acetic acid-mediated degradation. The red-shift of maximum emission wavelength indicated that Fe(II)-assisted acid induced molecular unfolding of SPI and increased surface hydrophobicity. Investigation of protein secondary structure revealed that Fe(II)-assisted acid treatment decreased the β-sheet structure by 4.65% and increased the α-helical content by 7.37%. This demonstrated that Fe(II) and acetic acid synergistically degrade ANFs by altering protein conformations in SBM.