The e β ect of adding steam (at 0Γ6 and 1Γ2 bar) and water (1Γ9% and 64% of the Γux of soy grits) in a conventional barrel type conditioner and its e β ects on protein dispersibility index (PDI), nitrogen solubility in 0Γ2% KOH and trypsin inhibitor activity (TIA) of commercial soy grits was studied. In addition, conditioned soy grits were subjected to expander treatment at two di β erent screw speeds (2 and 3 rps) and PDI, NSI and TIA were measured. Analysis of variance was used to determine the e β ects of steam pressure, water addition and screw speed on the mentioned protein quality parameters. In addition, resultant temperature from steam addition was used in an analysis of covariance to determine the e β ects of temperature as a covariate, water addition and screw speed on protein quality parameters. A signiΓcant interaction for steam pressure and water addition was found on all parameters. The highest denaturation or inactivation of the protein was found at the combination incorporating high steam and high water addition. Screw speed during expander treatment did not signiΓcantly a β ect protein quality parameters. It was concluded both from this study and from literature that PDI is a better parameter to evaluate technological treatments when low amounts of motor power are dissipated (\110 kJ kg~1) and that NSI in 0Γ2% KOH is a better parameter to discriminate between technological treatments when moderate to high amounts of motor power are dissipated in soy grits. TIA decreased with increasing water or steam content. The e β ect of trypsine inhibitor inactivation in soy grits was highest at higher temperatures and was not a β ected by screw speed of the expander.