Ultrasound-enhanced interfacial adsorption and inactivation of soy trypsin inhibitors

In this study, liquid-liquid interfacial protein adsorption was proposed as a means of inactivating soy trypsin inhibitors (TIs, including Kunitz (KTI) and Bowman-Birk inhibitor (BBI)). Hexane-water was first selected as a model system to compare three emulsification methods (hand shaking, rotor-stator and ultrasound mixing). Ultrasound could generate the smallest and least polydisperse emulsion droplets, resulting in highest interfacial adsorption amount of KTI and BBI as well as the highest inactivation percentage of TIs (p < 0.05). Therefore, ultrasound was selected to further explore the effect of the non-aqueous phase on interfacial adsorption and inactivation kinetics of TIs in a food emulsion system containing vegetable oil (VTO). The adsorption amounts of KTI and BBI in the VTO-aqueous emulsion increased by similar to 25 % compared to the hexane-aqueous emulsion. In addition, the adsorption amounts of KTI and BBI were rapidly increased as a function of sonication time, especially for the hexane-aqueous emulsion system. This result suggests that such inactivation of TIs could be implemented in continuous systems for large-scale processing. Finally, the pathways of interface-induced inactivation of BBI and KTI were investigated based on separate experiments on individual BBI and KTI systems. The results showed that the interface adsorption caused the changes in the secondary and tertiary structure of KTI that led to its activitation. However, BBI was quite stable at the liquid-liquid interface without significant conformational change. Overall, ultrasound-assisted interfacial adsorption can be considered a rapid and highly efficient method to inactivate KTI.

Automated summary

Liquid-liquid interfacial protein adsorption was proposed as a method to inactivate soy trypsin inhibitors. Ultrasound mixing generated the smallest and most uniform emulsion droplets, resulting in the highest adsorption amount and inactivation percentage. The adsorption amount of trypsin inhibitors increased in the presence of vegetable oil and rapidly increased with sonication time. The pathways of interface-induced inactivation differed for different inhibitors. Overall, ultrasound-assisted interfacial adsorption is a rapid and efficient method to inactivate soy trypsin inhibitors.