Abstract: Soybean protein isolate microgel (SPIM) was prepare by extreme acid combined with heat induction. The structural changes and molecular interactions of the protein, and the microstructure and gel properties of the microgel were explored by fluorescence spectroscopy, infrared spectroscopy, and atomic force microscopy, and the effects of different heat induction temperatures (25, 45, 55, 65, 75 and 85 ℃) on the structure and properties of the microgel were evaluated. The results showed that the relative content of β-sheet increased during the formation of SPIM, and electrostatic interaction, hydrophobic interaction and hydrogen bonding were involved in the self-assembly of microgels. In addition, with increasing temperature, the surface hydrophobicity index of SPIM increased first and then decreased, and that the thermal stability gradually increased. Compared with extreme acid, the specific surface area, emulsifying activity, emulsion stability and water-holding capacity of the microgel formed by extreme acid combined with heat induction at 75 ℃ were significantly increased (P < 0.05). Overall, extreme acid combined with heat induction is an effective method to regulate the structure and properties of protein microgels, and the quality of microgels can be improved by precise temperature control.

Key words: soy protein isolate; extreme acid; heat induction; microgel; gel properties