Abstract:

The aims of the present study were to determine the effect of high-speed shearing before flavourzyme hydrolysis on the degree of hydrolysis (DH) of soybean protein isolate and to analyze the relationship between the DH and dispersibility of soy protein isolate (SPI) in an aqueous solution at the isoelectric point. The introduction of high-speed shearing effectively propelled the enzymatic modification of SPI with flavourzyme. As the hydrolysis time was prolonged from 0.5 to 2.0 h, both the DH and disperisibility of SPI showed a gradual rise. The optimal shearing treatment conditions were found to be: substrate concentration, 100 g/L; shearing rate, 6000 r/min; and shearing duration, 4 min, and the DH of SPI was increased from 1.92% to 4.16% and the disperisibility at the isoelectric point from 20.62% to 46.82% under these conditions, reaching 3.22- and 2.27-fold increments, respectively, but the time required for the completion of enzymatic modification was shortened from 4.5 to 2.0 h.

Key words: soy protein isolate, high-speed shearing, degree of hydrolysis, dispersibility