Optimization of the effect of physical treatment on soybean trypsin inhibitor activity by response surface methodology

The purpose of this study was to determine the effects of physical treatment, including thermal, ultrasound and supercritical carbon dioxide (SC-C0₂) on the decrease of the soybean trypsin inhibitors (STIs) under various experimental conditions. In general, the results obtained indicated that the water bath heating, microwave heating and ultrasound treatment effectively decreased STI activity by 55.11, 22.37 and 38.81% at 120, 4 and 120 min, respectively, as compared to control. However, gradual increase of STI activity of 3.47% was observed with SC-C0₂-treatment. SDS-PAGE activity staining determined expected molecular size of the Kunitz Trypsin Inhibitor (KTI) protein through various treatments demonstrating that thermal and ultrasound were more effective to reduce STI activity according to the 50% inhibition of an enzymatic reaction assay (I₅₀). Furthermore, response surface methodology (RSM) was applied to determine the optimal inhibition rate by effective treatments that gave ideal inactivation of STI by the factor interactions. Applying the model method, desirable condition was formulated and performed for STI inactivation. The present study concludes that the potential of decrease of STI activity was achieved by various physical treatments, demonstrating the favourable conditions of efficient treatments by the treatment interactions in order to select suitable process for soybean processing.