Effect of pulsed electric field on the secondary structure and thermal properties of soy protein isolate

Changes of structure and thermal stability of soy protein isolate after pulsed electric field treatment were analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC). When the applied pulsed electric field (PEF) treatment intensity was over 35 kV/cm, the amino acid side chain, anti-parallel b-sheets, b-turn as well as b-sheets in soy protein isolate (SPI) secondary structure were significantly changed, which suggested that PEF treatment might be a new processing method for SPI; the dipole moments of some bonds, such as C=O, C–O, and C–O–C were partially polarized, accompanying with complete denaturation of b-conglycinin and glycinin obtained from DSC. Furthermore, selfreassembly from b-turn to a-helix in SPI structure abruptly happened under intense PEF treatment condition, which suggested that the PEF treatment had induced change of the orientation of a-helix dipole moment to stabilize a-helix. This observation implies that PEF treatment technique may be a novel method for preparation of protein nanotube.