Physicochemical modifications of high-pressure-treated soybean protein isolates

Changes induced by high pressure (HP) treatment (200-600 MPa) on soybean protein isolates (SP1) at pH 3 (SP13) and pH 8 (SP18) were analyzed. Changes in protein solubility, surface hydrophobicity (Ho), and free sulfhydryl content (SHF) were determined. Protein aggregation and denaturation and changes in secondary structure were also studied. An increase in protein Ho and aggregation, a reduction of free SH, and a partial unfolding of 7S and 11S fractions were observed in HP-treated SP18. Changes in secondary structure were also detected, which led to a more disordered structure. HP-treated SP13 was partially denatured and presented insoluble aggregates. A major molecular unfolding, a decrease of thermal stability, and an increase of protein solubility and Ho were also detected. At 400 and 600 MPa, a decrease of the SHF and a total denaturation were observed.