Abstract: The ultrasonic extraction of soy protein from defatted soy flakes and the effects of ultrasonic treatment on the functionality of soy protein isolates （SPI） were studied．The results show that the ultrasonic treatment could obviously increase the extraction of protein from different denatured defatted soy flakes．The protein extraction of defatted soy flakes and white flakes with ultrasonic treatment at300● W and12●kHz for8●min were73．43％ and90．28％ respectively‚but only49．58％ and66．54％ with conventional stirring extraction at 45 ℃ for 1 h．SDS-PAGE and GPC analyses show that ultrasonic treatment mainly affects the 7S components of soy protein．The ultrasonic treatment can also improve the functionality of soy protein isolates （SPI） obviously．The emulsifying property of SPI increased while the viscosity decreased with ultrasonic treatment．

Key words: ultrasonification, soy protein, extraction, functionality